- organic compound, single-axis carboxylic acid composition CH 3 COOH. Under normal conditions, it is a colorless liquid with a sharp smell. The melting point of pure acid is somewhat lower than room temperature, it turns into colorless crystals when freezing - it gave it technical name ice acetic acid.
The name of the acid is formed by the word vinegar, What comes from the lat. Acetum. - sour wine. According to the IUPAC nomenclature, it is a systematic name yetanova Acid, which characterizes the connection as a derivative of ethane. Since the acid molecule has in its composition a functional group of acetyl CH 3 CO (conventional designation AC) Its formula can also be written as Acoh. In the context of acid-base interactions with a symbol AC Sometimes acetate-anion CH 3 COO is affected - - in this case, the formula will have a record HAC.
Interacting with metals, alkalis and alcohols, acetic acid forms a number of salts and esters - acetates (eetanoival).
Acetic acid is one of the basic products of industrial organic synthesis. More than 65% of the global acetic acid production is based on the manufacture of polymers, cellulose derivatives and vinyl acetate. Polyvinyl acetate is the basis of many ґvintage coatings and paints. With acetate cellulose, acetate fiber is made. Acetic acid and its esters are important industrial solvents and extractants.
General
Acetic acid is known to humanity from ancient times. Vinegar, 4-12% acetic acid solution in water, as a wine fermentation product received a wide whistle for more than 5,000 years ago, primarily like a food preservative. The ancient Greek Hippocrates doctor used acid solutions as an antiseptic, as well as in the composition of non-phones from numerous diseases, including fever, constipation, gastric ulcers, pleurisy.
Acetic acid is in low concentrations in many plant and animal systems. It, in particular, is synthesized by the bacteria of the genus Acetobacter. and Clostridium. Among Roda Acetobacter. most effectively view Acetobacter Aceti.
In 1996, American scientists were informed about the observation of acetic acid molecules in the gas-dust cloud Sagittarius B2. Such discovery was first implemented using interferometric equipment.
Physical properties
Acetic acid at a standard state is a colorless liquid with a sharp smell. When freezing at a temperature of 16,635 ° C, it turns into transparent crystals (Ice acetic acid).
Acetic acid is indefinitely mixed with water, forms a significant amount of azeotropic mixtures with organic solvents:
Other physical properties:
- critical pressure of 5.79 MPa;
- critical temperature 321.6 ° C;
- specific heat capacity 2 010 J / (kg · k) (at 17 ° C);
- surface tension 27.8 · 10 -3 J / m² (at 20 ° C);
- corrosion activity of a 10% aqueous solution with respect to Art. 3 2.97 g / (h · m²) (20 ° C).
Obtaining
The synthesis of acetic acid solutions (vinegar) is carried out mainly by the method of fermentation, and to obtain pure acid, methods of carbonylation of methanol, oxidation of butane and ethannel are used in significant scales. The main method is obtaining from methanol.
Methanol carbonylation
The possibility of obtaining acetic acid from methanol was opened in the German concern BASF in 1913:
In 1938, BASF employee Walter Repe demonstrated the efficiency of using metal carbonyl catalysts VIIIB Groups (Group 9), in particular, cobalt carbonyl. The first full-scale production with the use of the cobalt catalyst was deployed in 1960 in Ludwigsgafenius, Germany.
In the late 1960s, Monsanto developed a new type of rhodium-based catalysts, which had significantly higher activity and selectivity compared to cobalt: Even at atmospheric pressure, the end of the final product was 90-99%. In 1986, this method acquired BP Chemicals and transferred it to the improvement of Celanese.
In the early 1990s, Monsanto patented the use of a new, iridium, catalyst. Its advantage was greater stable and smaller than liquid by-products. "BP" acquired the rights to this patent and implemented in production called cativa method (eng. Cativa Process).
BASF method
In the production of BASF method, the catalyst is carbonyl cobalt, which in situ. Get Cobalt (II) from iodide:
In the reaction system, carbonyl is formed activated and in the future it is in the form of a complex -:
In the first stage, the starting methanol interacts with iodine, which is a concomitant product of the synthesis of carbonyl, with the formation of iodomethane:
Yodomethane reacts with carbonyl:
Subsequently, carbonylation is carried out that leads to a complex acylbony intermediate:
Under the action of iodide ions, the complex decomposes, releasing the catalyst and acetylodide, which is hydrolyzed to acetic acid:
By the on-site products in this cycle is methane, ethanal, ethanol, propionic acid, alkyl acetates, 2-eethylbutane-1-ol. About 2.5% of methanol is converted to methane, and 4.5% on liquid by-products. 10% carbon monoxide is oxidized to dioxide:
For the carbonylation reaction of methanol, partial pressure of the starting materials are extremely important. Thus, the yield of the final product reaches 70% depending on the supply of carbon monoxide and 90% depending on methanol.
MONSANTO method
According to the MONSANTO method, the catalyst is diodeodicarbonyl sodes - which synthesize in situ. From iodide Rhodium (III) in aquatic or alcohol environment.
Celanese enhanced this method, adding its acid optimization cycle, when a minor additional amount of acetic acid in the form of acetate ions was supplied to the catalyst and increased its effectiveness at low concentrations of the initial compounds.
Synthesis is carried out at a temperature of 150-200 ° C and a pressure of 3.3-3.6 MPa.
Cativa method
The Monsanto method is the Cativa method. Here, the catalyst is the charged complex.
Compared to a rhodium catalyst, Iridiyevaya has the advantages and disadvantages: so, the oxidation of iridium iodomethane occurs 150-200 times faster, but the migration process of the methyl group takes place at 10,5 -10 6 times slower, besides the formation of methane by-product for Iridiyevoy catalyst above.
Oxidation of ethannel
The precursor for obtaining acetic acid is ethanol, which is synthesized by the oxidation of ethanol in the presence of silver salts:
Aldehyde oxidation occurs on a radical mechanism using the initiator:
The reaction passes through the stage of the formation of a peroxoacetable radical:
The resulting peroxoacetate acid reacts with acetaldehyde to form acetaldehyde-duratage, which, according to the mechanism of rearrangement of the Bayer - Wiliger, decomposes on acetic acid:
The by-product is methyl formate, which is formed as a result of migration of the methyl group.
Catalysts of interactions are cobalt or manganese salts. They also play an important role in reducing the amount of peracetate radicals in the reaction system, thereby preventing the formation of explosive concentrations:
The interactions on this method are carried out at a temperature of 60-80 ° C and a pressure of 0.3-1.0 MPa. The conversion of aldehyde into acetate acid usually occurs with a yield of more than 90% and with an acid selectivity of more than 95%.
Oxidation of hydrocarbons
Acetic acid can be obtained from butane and light oil fractions. This method is one of the most common thanks to the low cost of hydrocarbon raw materials. In the presence of metal cobalt type metal catalysts, chromium, manganese, butane is oxidized by air:
The main by-products are acetaldehyde and butanone.
Fermentation
Some bacteria, in particular, kind Acetobacter. and Clostridium, They produce acid in the process of its livelihoods. The use of such fermentation processes is known for more than a long time. Thus, low-centered acetic acid is formed, which fully satisfies household needs.
The types of bacteria are attracted to enzymatic production. Acetobacter Aceti. And artificially derived Clostridium ThermoaceTicum. For feeding bacteria use sugar-containing raw materials - glucose, xylose, and so on.:
A significant advantage of this method is the complete environmental friendliness of production.
Chemical properties
In the gas phase, hydrogen bonds arise between acid molecules, so they are mainly in dimmer form (also known tetramers):
In addition, the formation of a hydrated dimer is possible: molecules are combined with each other by only one bond, and the free carboxyl and hydroxyl groups are joined by hydrogen bonds on one water molecule. The degree of conversion to dimeric structures increases with an increase in the concentration of the solution and decreases with increasing temperature.
Acetic acid is a typical carboxylic acid, it is involved in all reactions characteristic of this series of compounds. In an aqueous solution of acid disintegrates and gives ion H + water molecules, forming a structure with two equal connections C-O:
Showing acidic properties, acetic acid reacts with active metals, oxides and hydrides of metals, organometallic compounds, ammonia, forming a number of salts - acetates.
Organic acetates are esters - acid interaction products with alcohols:
Condensation of acid with ethen synthesize vinyl acetate - industrially important compound, polyvinyl acetate monomer:
When exposed to strong dehydrating agents (type P 2 O 5), acetic anhydride is formed. A similar result with the participation of some chlorination agents (thionyl chloride, phosgene) is then the synthesis of anhydride passes through the stage of obtaining acetyl chloride.
Passing a preheated pair of acids over the catalyst (manganese oxides, thorium, zirconium), you can synthesize acetone (with a yield of about 80%):
When heated to 600 ° C, acetic acid is dehydrated to Katen - Retenon:
Toxicity
Being in a state of steam in the air, the acid damages the eyes, the nose and the throat at a concentration of more than 10 mg / m³. Serious consequences are observed with a ten-day repeating action of air polluted acid with a content of up to 26 mg / m³.
Low-centered acetic acid solutions (about 5%) can irritate mucous membranes. Concentrated acid greatly damages the skin at contact: in case of its hit, it is necessary to wash the affected area with a large amount of water or a solution of food soda. By swallowing acetic acid, pain in the esophagus and mouth is observed, this can lead to the appearance of nausea and breathing problems. In this case, it is necessary to rinse the oral cavity and consult a doctor.
Toxic doses in the consumption of acid by a person are not exactly known. The half-dollar dose for rats is 3310 mg / kg, for rabbits - 1200 mg / kg. Consumption by man 89-90 g of pure acid is extremely dangerous, and the maximum number for daily consumption is 2.1 g.
Application
The use of acetic acid is quite diverse. In the chemical industry, plastic masses produce, various dyes, medicinal substances, artificial fiber (acetate silk), non-flammable film and many other substances. Acetic acid salts are an acetates of aluminum, chromium, iron - used as a dreach when painting tissues. Acetic acid has widespread use and as a solvent.
In the food industry, it is used as a preservative, an acidity regulator and flavored seasoning; In the European system of food additives, acetic acid has a code E260.
Acid is used in a salty-acid processing of the crusar zone of the reservoir as a stabilizer (in order to stabilize the reaction products) from the falling out of the wrecks of gel-shaped iron compounds (precipitate). Depending on the iron content in the acidic solution (from 0.01 to 0.5%), they take 1-3% acetic acid. For the preparation of working solutions, both synthetic acid and woodymic technical purified are used.
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Acetic acid (methan-marginal, etching acid)CH 3 COOH - colorless liquid with a sharp odor and sour taste. Anhydrous acetic acid called"Ice". Melting point is16, 75 ° C, boiling point118, 1 °; 17, 1 ° at a pressure of 10 mm. RT. Post, 42, 4 ° at 40 mm., 62, 2 ° at 100 mm., 98, 1 ° at 400 mm. and 109 ° at 560 mm. Mercury pillar.
The specific capacity of acetic acid is equal0, 480 kal / g. hail., q combustion 209, 4 kcal / mol.
Acetic acid belongs to weak acids, dissociation constant K \u003d1, 75 . 10 -5 . It is mixed in all respects with water, alcohol, ether, benzene and insoluble in the servo carbon. When diluting acetic acid with water, the volume of the solution is reduced. Maximum density1, 0748 g / cm 3 responsible monohydrate.
Acetic acid is the first of the acids, which became known to humanity (in the form of vinegar formed during the zealing of wine). In concentrated form, it was received by the staff in1700 year, and the composition was installed by Berzelius in1814 year. Acetic acid is widespread in plants both in free form and in the form of salts and esters; It is formed during rotting and fermentation of dairy products. Transformation of alcohol liquids into vinegar (3-15% acetic acid) occurs under the action of bacteria« acetic fungus»Micoderma Aceti. . From the distorted liquid distillation get80% acetic acid is acetic essence. Acetic acid on a limited scale is obtained from« wood vinegar» - One of the products of dry distillation of wood.
The main industrial method for obtaining acetic acid consists in oxidation of acetaldehyde, synthesizedfrom acetylene for coaching reactions. Oxidation is produced by air or oxygen when60 ° and catalysis (CH 3 SOS) 2 m n. This way is obtained95-97% acetic acid. In the presence of acetatecobalt and copper at 40 ° a mixture of acetic acid is obtained (50-55%), acetic anhydride (30-35%) and water (~ 10%). The mixture is separated by distillation. The technical value for the preparation of acetic acid is also the oxidation of ethylene, ethyl alcohol and others, as well as actionsulfuric acid on nitroean.
Clean acetic acid is obtained from industrial products to rectification.
Hydroxyl group of acetic acid is very reactive and can exchange on halogens,SH, OC 2 H 5, NH 2, NHNH 2, N 3, NHOH and others with the formation of its different derivatives, for example, acetylchloride CH 3 SOS L , acetic anhydride(CH 3 CO) 2 O, acetamide CH 3 C N H 2, Azide CH 3 with N 3 ; alcohols acetic acid esterifies, forming esters (acetates) CH 3 Soo R. The simplest of which is the volatile liquids with a fruit smell (for example, amylacetate and isoamila acetate« pear essence»), less often with floral odor (tert-butylcyclohexyl acetate).
The physical properties of some acetic acid esters are given in the table; they are widely used as solvents (especially ethyl acetate) for nitrocellulosic varnishes, glyphthalic and polyester resins, in the production of film andcelluloid as well as in the food industry and perfumery. In the production of polymers, artificial fibers, varnishes and adhesives based on vinyl acetate play a significant role.
Acetic acid finds an extensive and diverse application. The technique among its most common reactions includes the introduction of acetyl group of CH 3 Co with which protects, for example, in aromatic aminesNH 2 - a group of oxidation during non-nitration; Receive a number of medicinal substances (aspirin , Penacetin and others).
Significant amounts of acetic acid go to the production of acetone, acetylcellulose, synthetic dyes, are used for painting and tissue printing and in the food industry. Basic acetic saltsAL, FE, CR And others serve as rubbing during dye; They provide a durable dye dye with textile fiber.
Pairs of acetic acid irritate the mucous membranes of the upper respiratory tract. The chronic action of vapors leads to the diseases of the nasopharynx and to conjunctivitis. The maximum permissible concentration of its vapors in the air0.005 mg / l. Solutions with concentration Above 30% cause burns.
One of the first acids, which became known to people in antiquity, was acetic acid. It was found randomly - due to the appearance of vinegar when drying wine. In 1700, the stall received a concentrated species of the chemical variety of fluid, and in 1814 - Bercelyus has established an accurate composition.
The preparation of acetic acid is possible in different ways, but it is used quite widely in many directions of economic activity.
Acetic acid is a synthetic product of fermentation of carbohydrates and alcohols, as well as a natural whisening of dry grape wines. Taking part in the metabolic process in the human body, this acid is a dietary supplement used for the preparation of marinades and conservation.
Acid derivatives are vinegar - 3-9%, and acetic essence is 70-80%. Esters and acetic acid salts are called acetates. The composition of the usual vinegar, to which each mistress is accustomed, is an ascorbic, dairy, apple, acetic acid. Every year almost 5 million tons of acetic acid are produced in the world.
The transportation of acid at different distances is carried out in rail or car tanks made from specialized stainless steel stamps. In warehouse conditions, it is stored in hermetic tanks, containers, barrels under canopies or indoors. Pouring and store substance in the polymer container can be within one calendar month.
Qualitative acetic acid characteristics
Colorless liquid with an acidic taste and a rescued smell, which is acetic acid, has a number of certain advantages. Specific properties make acid essential in many chemical compounds and domestic products.
Acetic acid, as one of the carboxylic representatives, has the ability to manifest high reactivity. Entering the most different substances in the reaction, the acid becomes the initiator of the compounds with the functional derivatives. Thanks to such reactions, it becomes possible:
- Salts formation;
- Formation of amides;
- The formation of esters.
A number of specific technical requirements are presented to acetic acid. The liquid should be dissolved in water, not to have mechanical impurities and have the established proportions of high-quality components.
Main areas of use of acetic acid E-260
The variety of areas in which acetic acid is applicable is quite large. This acid is an indispensable component of many medicinal preparations - For example, fenacetin, aspirin and other varieties. The aromatic amines of the NH2-groups are protected during the nitration process by the introduction of the CH3SO acetyl group - it is also one of the most common reactions in which acetic acid is entering.
A rather important role is played by a substance in the manufacture of acetylcellulose, acetone, various synthetic dyes. It is not necessary without its participation production of various perfumery and non-combustible films.
Acetic acid is often applicable in the food industry - as a dietary supplement E-260. Canning and household cooking are also a successful field of action and the use of high-quality natural additive.
When painting the main types of acetic acid salts play the roles of special doors, providing a stable communication of textile fibers with a dye. These salts are often used in the fight against the most persistent varieties of pest plants.
Precautions when working with acetic acid
Acetic acid is considered a flammable liquid, which is assigned a third hazard class - in accordance with the classification of substances by the degree of dangerous impact on the body. For any work with this type of acid, specialists use individual modern protection tools (filtering gas masks).
Even a nutritional supplement E-260 may be toxic for the human body, however, the degree of exposure will depend on the quality of dilution with water concentrated acetic acid. Solutions, the concentration of acid in which exceeds the level of 30%, are considered life-threatening. In contact with the skin and mucous membranes, high concentration acetic acid will cause strongest chemical burns.
In this case, the method of obtaining an acid does not play a special role in its toxicological orientation, and a dose of 20 ml can be fatal. Various consequences can be destructive for many human organs - ranging from oral mucous and respiratory tract and ending with the stomach and esophagus.
In case of careless, the acid inside is important to drink as much liquid as possible before the arrival of the physicians, but in no case causing vomiting. The re-passing of substances by the body may re-burn organs. In the future, it is necessary to wash the stomach with the help of probe and hospitalization.
Undoubtedly, the most versatile from the known solvents relating to aliphatic mono-zero acids is all known acetic acid. It also has other names: acetic essence or stencil acid. Cheapness and accessibility at different concentrations (from 3 to 100%) of this substance, its stability and simplicity of purification, led to the fact that today it is the best and most well-known means with properties to dissolve most of the substances of organic origin, which are in great demand in various fields human activity.
Acetic acid was the only one who knew the ancient Greeks. From here and its name: "OKSOS" - sour, sour taste. Acetic acid is the simplest form of organic acids, which are an integral part of plant and animal fats. In small concentrations, it is present in food and beverage products and participates in metabolic processes in the ripening of fruits. Acetic acid is often found in plants, in animal discharge. Salts and acetic esters are called acetates.
Acetic acid is weak (dissociates in aqueous solution only partially). However, since the acidic medium suppresses the life activity of microorganisms, acetic acid is used in preserving food, for example, as part of marinades.
Acetic acid is obtained by oxidation of acetaldehyde and other methods, food acetic acid acetic acid fermentation of ethanol. Used to obtain medicinal and fragrant substances, such as a solvent (for example, in the production of cellulose acetate), in the form of a table vinegar in the manufacture of seasonings, marinades, canned food. Acetic acid participates in many metabolic processes in living organisms. This is one of the volatile acids present in almost all foods, sour taste and the main component of vinegar.
The purpose of this work: to explore the properties, production and use of acetic acid.
Tasks of this study:
1. To tell about the history of the opening of acetic acid
2. To study the properties of acetic acid
3. Describe methods for producing acetic acid
4. Reveal the features of the use of acetic acid
1. Opening acetic acid
The structure of acetic acid is interested in chemists since the opening of a dum of trichloroacetic acid, since this discovery caused a blow to the maintenance of the electrochemical theory of Berzelius. The latter, distributing elements on electropositive and electronegative, did not recognize the possibilities of substitution in organic substances, without a deep change in their chemical properties, hydrogen (electropositive element) with chlorine (element electronegative), and meanwhile by observations of Dumas ("Comptes Rendus" of the Paris Academy, 1839 ) It turned out that "the introduction of chlorine at the place of hydrogen does not change completely external properties of the molecule ..." why duma and wonders "whether electrochemical views and ideas about polarity attributed to molecules (atoms) of simple bodies, on such clear facts to They could be considered the subjects of the unconditional faith; if they should be considered as hypotheses, are these hypotheses for the facts suitable? ... should be recognized, it continues that it is different. In an inorganic chemistry, an isomorphism, theory, based on on facts, as well known, little consonant with electrochemical theories. In organic chemical And the same role is played by the theory of substitution ... and maybe the future will show that both views are more closely related between themselves that they leak out of the same reasons and can be summarized under the same name. In the meantime, on the basis of the conversion of U. Acid in chloroacetic and aldehyde in chloroldehyde (chloral) and from the fact that in these cases, all hydrogen can be substituted with a chlorine equal to it without changing the main chemical nature of the substance, it can be deducted that in organic chemistry There are types that are preserved and then when we introduce equal volumes of chlorine, bromine and iodine to the place of hydrogen. This means that the theory of substitution rests on the facts and, with the most brilliant in organic chemistry. ". Renting this excerpt in its annual report of the Swedish Academy (" Jahresbericht etc. ", vol. 19, 1840, p. 370). Burtsellius notices: "Duma prepared a compound to which it gives the rational formula C4Cl6O3 + H2O (modern atomic weights; trichloroacetic acid is considered as an anhydride compound with water.); This observation is counted to Faits Les Plus Eclatants De La Chimie Organique; This is the basis of its replacement theory. which, in his opinion, the tipping of electrochemical theories ..., and meanwhile it turns out that it is only its formula to write somewhat differently to have a compound of oxalous acid. With respective chloride, C2Cl6 + C2O4H2, which remains connected to oxalic acid and in acid, and in salts. We, therefore, are dealing with such a native of the compound, there are many examples of which are known; Many ... both simple and complex radicals possess the property that their oxygen-containing part can enter into a connection with the bases and to lose them, without losing touch with the chlorine-containing part. This appearance is not given in Dumas and have not been exposed to experienced verification, and meanwhile, if it is true, then the new teaching, incompatible, in Dumas, with the most theoretical ideas, are escaped from under the feet of the soil and it should fall. "Enumeration Some inorganic compounds, like, in its opinion, chloroacetic acid (the chromic acid anhydride chloride is also given between the Berzelius - Cro2Cl2, which he believed for the compound of the suplorn chromium (unknown and by this time) with a chromium anhydride: 3CRO2CL2 \u003d CRCl6 + 2CRO3) , Britzelius continues: "Duma chloroacetic acid is obviously belonging to this class of compounds; In it, carbon radical is connected with oxygen, and with chlorine. It may be, therefore, oxalic acid, in which half oxygen is substituted with chlorine, or a compound of 1 atom (molecules) of oxalic acid with 1 atom (molecule) of half-cooler carbon - C2Cl6. The first assumption cannot be accepted, because it allows the possibility of substitution of chlorine 11/2, oxygen atoms (according to bezer oxalic acid was C2O3.). In Dumas also holds the third view, completely incompatible with the two foregoing, on which chlorine is not replaced by oxygen, and the electropositive hydrogen, forming a C4Cl6 hydrocarbon, which has the same properties of a complex radical, as well as C4H6 or acetyl, and a capable allegedly with 3 oxygen atoms to give acid Celed according to the properties from W., but, as can be seen from the comparison (their physical properties), quite excellent from it. "As far as Burtselius was deeply convinced of the various constitution of acetic and trichloroacetic acid, it is clear from the comment made by him in that And year ("Jahresb.", 19, 1840, 558) Regarding the article Gerar ("Journ. F. Pr. Ch.", XIV, 17): "Gerard, he says, expressed a new look at the composition of alcohol, ether and their derivatives; It is as follows: The known chromium, oxygen and chlorine compound has a formula \u003d Cro2Cl2, chlorine replaces an oxygen atom in it (is meant by Berzelius 1 oxygen atom of chromium anhydride - CRO3). W. Acid C4H6 + 3O encompasses 2 atoms (molecules) of oxalic acid, of which in one all oxygen is substituted with hydrogen \u003d C2O3 + C2H6. And such a game in formulas filled 37 pages. But next year, Dumas, developing the idea of \u200b\u200btypes, indicated that, speaking of the very title of properties of the property and trichloroacetic acid, he meant the identity of their chemical properties, visually expressing, for example, in the analogy of them under the influence of alkalis: C2H3O2K + KOH \u003d CH4 + K2CO8 and C2Cl3O2K + KOH \u003d CHCl3 + K2CO8, since CH4 and CHCl3 are representatives of the same mechanical type. On the other hand, Lubih and Gremis publicly spoke in favor of greater simplicity achieved on the soil of substitution theory, in the consideration of chloro-producing ordinary ether and the ether of the forming and U. acid, obtained by Malagetti, and Britzelius, yielding the pressure of new facts in the 5th ed. His "Lehrbuch Der Chemie" (preface is marked by November 1842), forgetting his sharp review about Gerard, found it possible to write the following: "If we recall the transformation (in the text decomposition) of acetic acid under the influence of chlorine in chloro-eyed acid (chloroable - chloroxalsaure - Britzelius calls trichloroacetic acid. ("Lehrbuch", 5 ed., P. 629).), It seems possible another look at the composition of acetic acid (acetic acid is called Berzelius Acetylsaure.), Namely - it can be combined oxalic acid, In which the combined group (Paarling) is C2H6, just as a combined group in chloroable acid is C2Cl6, and then the effect of chlorine on acetic acid would only be in converting C2H6 in C2Cl6. It is clear, it is impossible to decide whether such a representation is more correct. .., however, it is useful to pay attention to it. "
Thus, Berzelius had to admit the possibility of substitution of hydrogen by chlorine without changing the chemical function of the original body in which the replacement occurs. Without stopping at the appendix of his views to other compounds, I turn to the collee works, which for acetic acid, and then for other limit mono-abnormal acids, found a number of facts that harmonized with the views of Bercelius (Gerard). The initial point for the works of Kolbe served as a crystalline substance, the composition of CCL4SO2, obtained earlier by Berzelius and Marsa under the action of royal vodka on CS2 and formed in the collee under action on a CS2 wet chlorine. Near the conversion of Kolbe (see Kolbe, "Beitrage ZNR Kenntniss der Gepaarten Verbindungen" ("Ann. Ch. U. Ph.", 54, 1845, 145).) Showed that this body represents, expressing modern tongue , chlorine trichloromethylsulfonic acid anhydride, CCL4SO2 \u003d CCL3.SO2CL (Kohlensuperchlorid schwefligsaures call), capable of alkaliing to give salts of appropriate acid - CCL3.SO2 (OH) [on Colba but + C2Cl3S2O5 - ChlorkohlenunurschwefelSault] (Atomic weights: H \u003d 2 , CL \u003d 71, C \u003d 12 and O \u003d 16; And therefore, with modern atomic scales, it is C4SL6S2O6H2.), Which is under the influence of zinc, first replaces one atom with hydrogen, forming acid CHCL2.SO2 (OH) [by Colba - Wasserhaltige ChlorFormylunterschwefelSaure (Burtsellius ("Jahresb." 25, 1846, 91) Notes that it is correct to consider it with a combination of S2O5 dithionic acid with chloroforming, why it CCL3SO2 (OH) calls Kohlensuperchlorurur (C2Cl6) - DithionSaure (S2O5). Hydrate water, as usual, bezer Not taken into account.), And then another, forming the acid CH2CL.SO2 (OH) [on the collee - chlororelialunterschwefelsaure], and, finally, when restoring the current or potassium amalgam (the reaction is shortly before it was applied And the melt to restore trichloroacetic acid into acetic.) Replaces hydrogen and all three CL atoms, forming methyl sulphonic acid. Ch3.SO2 (OH) [Colbet - Methylunterschwefelsaure]. The analogy of these compounds with chloroacetic acids was involuntarily striking; Indeed, at the then formulas, two parallel rows were obtained, as seen from the following plate: H2O + C2Cl6.S2O5 H2O + C2Cl6.C2O3 H2O + C2H2CL4.S2O5 H2O + C2H2CL4.C2O3 H2H2CL4.C2O3 H2O + C2H4CL2.S2O5 H2O + C2H4CL2.C2O3 H2O + C2H6. S2O5 H2O + C2H6.C2O3 This has not escaped from Colba, which notes (I. p. 181): "To the combined sulfuric acids described above and directly in chloro-carbonnetic acid (above - H2O + C2Cl6.s2O5) adjoins chlorosal acid, known as chloroacetic acid. Liquid chloro-carbon - CCl (Sl \u003d 71, C \u003d 12; Now we write C2Cl4 is chloroethylene.), As you know, turns into the light under the influence of chlorine in hexakhloroethane (on the then nomenclature - Kohlensuperchlorurur), And we can expect that if it is simultaneously subjected to water with water, it, like a bismuth chloride, chlorine antimony, etc., at the time of education, replace chlorine oxygen. The experience confirmed the assumption. " Under the action of light and chlorine on C2Cl4, which was under water, the coloe was obtained on a row with hexachloroethane and trichloroacetic acid and expressed the conversion by such an equation: (since C2Cl4 can be obtained from CCl4 when it is transmitted through an anti-mounted) tube, and the CCL4 is formed under action, When heated, CL2 on CS2, then the Kolbe reaction was the first synthesis of acetic acid from the elements. ) "It is formed simultaneously and free oxalous acids. It is difficult to solve, since the chlorine immediately oxidizes it into acetic acid" ... the view of the bercelium on chloroacetic acid "an amazing way (AUF EINE TiberRaschende Weise) is confirmed by the existence and parallelism of the properties of combined sulfuric acids, and, as it seems to me (says Kolba I. p. p. 186), it comes out of the region of the hypotheses and acquires a high degree of probability. For if chloroHlenoxaure (chlorkohlenoxalsaure, so now Kolba calls chloroacetic acid.) It has a composition similar to the composition of chlorogen Acids, then we must consider acetic acid that meets the methyl services, for the combined acid and consider it, as a methyl grinding: C2H6.C2O3 (this is a look expressed by Gerarger). It is not incredible that we will be forced in the future to take a significant number for compound acids. of those organic acids in which at present, by virtue of the limitedness of our information - we accept the hypothetical Ske radicals ... "" As for the phenomena of replacement in these combined acids, they receive a simple explanation in the fact that various, probably, isomorphic compounds are able to replace each other in the role of combined groups (ALS RARLINGE, L. with. Page 187), without changing the essentially acidic properties of the body combined with them! "Further experimental confirmation of this look We find in Article Frankland and Kolbe:" Ueber Die Chemische Constitution Der Sauren Der Reihe (CH2) 2NO4 Und Der Unter Den Namen "Nitrile" bekannten verbindungen "(" Ann. Chem. N. Pharm. ", 65, 1848, 288). Based on the presentation that all the acids of the series (CH2) 2NO4 are constructed like methylchic acid (now we write CNH2NO2 and call methyl spacing acid - acetic .), They notice the following: "If the formula H2O + H2.C2O3 represents the true expression of the rational composition of formic acid, i.e. if it is considered for the oxalic acid, combined with one equivalent of hydrogen (the expression is not true; instead of NG. Frankland and Kolbe consume a crossed letter, which is equivalent to 2 N.), it is easily due to the conversion at a high temperature of ammonium anti-oxygen in aqueous sinyl acid, because it is known, and the Dobereer is found that Razv Elvohisha Ammonium disintegrates when heated into water and cyan. Hydrogen combined in formic acid is involved in the reaction only by the fact that it connects with a cyan forms a sinyl acid: the reverse formation of formic acid from the blue influence of alkalishes represents nothing more than the repetition of the known conversion of the cyana dissolved in the water in oxalic acid and ammonia, With only the difference; That at the time of formation, oxalic acid is combined with hydrogen of blue acid. " The fact that benzene cyano (C6H5CN), for example, on Feling, does not have acidic properties and does not form Berlin Lazari can be, according to Kolbe and Frankland, put in parallel with the inability of chlorine chloride of ethyl to reaction with AGNO3, and the correctness of their collee and Frankland prove the synthesis according to the nitrile method (nitriles of them were obtained by distillation of sulfuric acids with KCN (method of Duma and Malagetty with Lebed): R. ".SO3 (OH) + KCN \u003d R.CN + KHSO4) acetic, propionova (on the then, method acetone,) and capronic acid, then next year Kolbe subjected to electrolysis alkali salts of mono-axial limit acids and, in accordance with its scheme, observed, with electrolysis of acetic acid, the formation of ethane, coalic acid and hydrogen: H2O + C2H6.C2O3 \u003d H2 +, and with valerian electrolysis - octane, coal acid and hydrogen: H2O + C8H18.C2O3 \u003d H2 +. However, it is impossible not to notice that the collee expected from acetic acid methyl (CH3), connected to hydrogen, i.e. . Bolo. gas, and from Valerian - butyl C4H9, also connected to hydrogen, i.e. C4H10 (it calls C4H9 Wallel), but in this expectation it is necessary to see the concession, the significant rights of citizenship of Gerard, who abandoned its former look at Acetic acid and considered it not for C4H8O4 what a formula, judging by cryoscopic data, it also possesses and in fact, and for C2H4O2, as written in all modern chemistry textbooks.
The collee works of acetic acid, and at the same time, and all other organic acids were finally clarified and the role of subsequent chemists was reduced only to the division - due to theoretical considerations and the authority of Gerard, the Colza formulas in half and to translate them to the language of structural views, so that the formula C2H6.C2O4H2 turned into CH3.CO (OH).
2. Properties of acetic acid
Carboxylic acids are organic compounds containing one or more carboxyl groups -Oson associated with a hydrocarbon radical.
The acid properties of carboxylic acids are due to the displacement of electron density to carbonyl oxygen and caused by this additional (compared to alcohols) of the polarization of the O-N communication.
In an aqueous solution, carboxylic acids dissociate on ions:
With an increase in the molecular weight solubility of acids in water decreases.
According to the number of carboxyl groups, acids are divided into monosular (monocarbonic) and multi-axis (dicarboxylic, tricarboxyle, etc.).
According to the nature of the hydrocarbon radical, the acids are distinguished, unsaturated and aromatic.
Systematic acid names are given by the name of the corresponding hydrocarbon with the addition of suffix -com And words acid . Trivial names are also used.
Some limit monoise acids
Carboxylic acids exhibit high reactivity. They react with different substances and form a variety of compounds, among which are of great importance functional derivatives . Compounds obtained as a result of reactions for carboxyl group.
2.1 formation of salts
a) when interacting with metals:
2RCOOH + Mg ® (RCOO) 2 Mg + H 2
b) in reactions with metals hydroxides:
2RCOOH + NaOH ® RCOONA + H 2 O
Instead of carboxylic acids, their halogen chidrides are often used:
Amides are also formed in the interaction of carboxylic acids (their halogenantrides or anhydrides) with organic ammonia derivatives (amines):
Amides play an important role in nature. Molecules of natural peptides and proteins are constructed from A-amino acids with the participation of amide groups - peptide ties.
Acetic (etching acid).
Formula: CH 3 - Soam; transparent colorless liquid with a sharp odor; Below the melting point (mp. 16.6 degrees c) similar to ice mass (therefore, concentrated acetic acid is also called icy acetic acid). Soluble in water, ethanol.
Table 1. Physical properties of acetic acid
Synthetic food acetic acid is a colorless, transparent, flammable liquid with a sharp smell of vinegar. Synthetic food acetic acid is obtained from methanol and carbon monoxide in the rhodium catalyst. Synthetic food acetic acid is used in the chemical, pharmaceutical and light industry, as well as in the food industry as a preservative. Formula CH 3 coxy.
Synthetic food acetic acid is produced concentrated (99.7%) and in the form of an aqueous solution (80%).
In physical and chemical indicators, synthetic food acetic acid must comply with the following standards:
Table 2. Basic technical requirements
| Name of the indicator | Norm |
| 1. Appearance | Colorless, transparent liquid without mechanical impurities |
| 2. Water solubility | Full, solution transparent |
| 3. Mass fraction of acetic acid,%, not less | 99,5 |
| 4. Mass fraction of acetic aldehyde,%, no more | 0,004 |
| 5. Mass fraction of formic acid,%, no more | 0,05 |
| 6. Mass fraction of sulfates (SO 4),%, no more | 0,0003 |
| 7. Mass fraction of chlorides (CL),%, no more | 0,0004 |
| 8. Mass fraction of heavy metals precipitated by hydrogen sulfide (PB),%, no more | 0,0004 |
| 9. Mass fraction of iron (Fe),%, no more | 0,0004 |
| 10. Mass fraction of non-volatile residue,%, no more | 0,004 |
| 11. Stability of the color of a solution of manganese-solid potassium, min, not less | 60 |
| 12. Mass fraction of substances oxidized by two-axis potassium, Cm 3 sodium thiosulfate solution, concentration C (Na 2 SO 3 * 5H 2 O) \u003d 0.1 mol / dm 3 (0.1h), no more | 5,0 |
Synthetic food acetic acid - flammable liquid, according to the degree of impact on the body refers to the substances of the 3rd hazard class. When working with acetic acid, individual protection means should be applied (filtering gas masks). First assistance in burns - abundant watering with water.
Synthetic food acetic acid is poured into pure railway tanks, tank trucks with an inner surface of stainless steel, in containers, containers and stainless steel barrels with a capacity of up to 275 dm3, as well as in glass bottles and polyethylene barrels with a capacity of up to 50 dm3. The polymer container is suitable for the bay and storage of acetic acid for one month. Synthetic food acetic acid is stored in sealed stainless steel tanks. Containers, containers, barrels, bottles and plastic flasks are stored in storage rooms or under a canopy. Co-storage with strong oxidizers (nitric acid, sulfuric acid, potassium permanganate, etc.) is not allowed.
It is transported in railway tanks made of stainless steel brand 12x18h10t or 10x17h13m2t, with the upper plum.
3. Preparation of acetic acid
Acetic acid is the most important chemical product, which is widely used in industry for the preparation of esters, monomers (vinyl acetate), in the food industry, etc. The world production reaches 5 million tons per year. The preparation of acetic acid until recently was based on petrochemical raw materials. In the Walker-process, ethylene in mild conditions is oxidized by air oxygen to acetaldehyde in the presence of the catalytic system PDCl2 and CuCl2. Next, acetaldehyde is oxidized to acetic acid:
CH2 \u003d CH2 + 1/2 O2 CH3CHO CH3COOH
Under another method, acetic acid is obtained by oxidizing H-butane at a temperature of 200 C and a pressure of 50 atm in the presence of a cobalt catalyst.
Elegant Walker Process is one of the symbols of the development of petrochemistry - gradually replaced by new methods based on the use of coal raw materials. Methods for obtaining acetic acid from methanol have been developed:
CH3OH + CO CH3COOH
This reaction having a large industrial value is an excellent example illustrating the successes of homogeneous catalysis. Since both components of the reaction - CH3OH and CO can be obtained from coal, the carbonylation process should become more economical as oil prices rise. There are two industrial methanol carbonylation process. In an older method developed at BASF, a cobalt catalyst was used, the reaction conditions were rigid: temperature 250? C and pressure 500-700 atm. In another process, a rhodium catalyst was used in another process, the reaction was carried out at lower temperatures (150-200 C) and pressure (1-40 atm). Interesting the history of the opening of this process. Scientists companies investigated hydraulication using riforifosphin catalysts. The technical director of the petrochemical department proposed to use the same catalyst for carbonylation of methanol. The results of the experiments turned out to be negative, and these were related to the difficulty of forming the metal-carbon connection. However, remembering the lecture of the company's consultant on the easiest oxidative accession of iodistan methyl to metal complexes, the researchers decided to add an iodine promoter to the reaction mixture and received a brilliant result that was first not believed. Such discovery was also made by scientists from the competing company "Union Carbide", those behind just a few months. A team of methanol carbonylation technology in just 5 months of intensive work created the industrial process of Monsanto, with which 150 thousand tons of acetic acid was obtained in 1970. This process was the harbingers of the area of \u200b\u200bscience, which was called C1 chemistry.
The carbonylation mechanism was carefully examined. Iodisty methyl necessary for the implementation of the reaction is obtained by equation
CH3OH + HI CH3I + H2O
The catalytic cycle can be presented as:
The flat-sized complex - (i) opsisibly joins the methyl, with the formation of a six-coordinate complex II, then as a result of the introduction of Methyl-Rhodes, acetylrody complex (III) is formed. The reducing elimination of acetic acid odanhydride regenerates the catalyst, and the hydrolysis of iodangide produces acetic acid.
Industrial acetic acid synthesis:
a) catalytic oxidation of butane
2ch3-CH2-CH2-CH3 + 5O2 T 4CH3COOH + 2H2O
b) heating the mixture of carbon oxide (II) and methanol on pressure catalyst
CH3OH + CO CH3COOH
Production of acetic acid fermentation (acetic acid fermentation).
Raw materials: ethanol-changing liquids (Wine, born juices), oxygen.
Auxiliary substances: the enzymes of acetic acid bacteria.
Chemical reaction: Ethanol is biocatalytically oxidized to acetic acid.
CH 2 - CH - He + O 2 CH 2 - Soam + H 2 O
Main product: acetic acid.
4. Application of acetic acid
Acetic acid is used to obtain medicinal and fragrant substances, as a solvent (for example, in the production of cellulose acetate), in the form of a table vinegar in the manufacture of seasonings, marinades, canned food.
An aqueous solution of acetic acid is used as a flavor and preservative means (seasoning to food, marinating mushrooms, vegetables).
The composition of the vinegar includes acids such as apple, dairy, ascorbic, acetic.
Apple vinegar (4% acetic acid)
Apple vinegar contains 20 most important minerals and microelements, as well as acetic, propionic, milk and citric acid, a number of enzymes and amino acids, valuable ballast substances, such as potash, pectin. Apple vinegar is widely used in the preparation of various dishes and preservation. It is perfectly combined with all sorts of salads, both fresh vegetables and meat and fish. It can marine meat, cucumbers, cabbage, capers, portulas, as well as truffles. However, in the west, apple vinegar is known more than its healing properties. It is used with elevated blood pressure, migraines, asthma, headache, alcoholism, dizziness, arthritis, diseases of the kidneys, high temperature, burns, bargaining, etc.
Healthy people are recommended every day to use a useful and refreshing drink: in a glass of water stiring a spoonful of honey and add 1 spoon of apple vinegar. Wishing to lose weight, we recommend every time during food drinking a glass of waste water with two spoons of apple vinegar.
Vinegar is widely used in home canning for the preparation of marinades of various fortresses. In folk medicine, vinegar is used as a non-specific antipyretic agent (by wiping the skin with a solution of water and vinegar in proportion 3: 1), as well as with headaches by the method of a ride. The use of vinegar is common in insect bite by means of compresses.
It is known to use alcohol vinegar in cosmetology. Namely to give softness and gloss hair after a chemical curling and permanent color. For this, hair is recommended to rinse with warm water with the addition of alcohol vinegar (per 1 liter of water - 3-4 spoons of vinegar).
Vinegar grape (4% acetic acid)
Grape vinegar is widely used by leading chefs not only Slovenia, but also around the world. In Slovenia, it is traditionally used in the preparation of various vegetable and seasonal salads (2-3 tbsp. Spoons on a salad bowl), because He gives the unique and refined taste of the dish. Also, the grape vinegar is perfectly combined with various fish salads and dishes from marine products. When cooking kebabs from various varieties of meat, but especially from pork, grape vinegar is simply indispensable.
Acetic acid is also used to produce medicines.
Aspirin tablets (EC) contain an active ingredient acetylsalicylic acid, which is acetic ester of salicylic acid.
Acetylsalicylic acid is produced by heating salicylic acid with anhydrous acetic acid in the presence of a small amount of sulfuric acid (as a catalyst).
When heated with sodium hydroxide (NaOH) in aqueous solution, acetylsalicylic acid is hydrolyzed to sodium salicylate and sodium acetate. When the medium is acidified, salicylic acid falls precipitated and can be identified by melting point (156-1600c). Another method of identifying salicylic acid, formed during hydrolysis, is staining its solution into a dark purple color when adding iron chloride (FECL3). Acetic acid present in the filtrate turns into heating with ethanol and sulfuric acid into ethoxyethanol, which can be easily recognized by its characteristic odor. In addition, acetylsalicylic acid can be identified using various chromatographic methods.
Acetylsalicylic acid crystallizes with the formation of colorless monoclinic polyhedra or needles, a little sour taste. They are stable in dry air, but in a humid medium, gradually hydrolyzed to salicylic acid and acetic acid (Leeson and Mattocks, 1958; Stempel, 1961). Clean substance is a white crystalline powder that almost does not possess the smell. The smell of acetic acid indicates that the substance began to hydrolyze. Acetylsalicylic acid is exposed to esterification under the action of alkaline hydroxides, alkaline bicarbonates, as well as in boiling water.
Acetylsalicylic acid has an anti-inflammatory, antipyretic, as well as an painful effect, and is widely used for feverish states, headaches, neuralgia, etc. and as an antheumatic agent.
Acetic acid is used in and chemical industry (production of acetylcellulose, from which acetate fiber is obtained, organic glass, a film; for the synthesis of dyes, medicines and esters), in the production of non-combustible films, perfumery products, solvents, during the synthesis of dyes, medicinal substances, such as , aspirin. Acetic acid salts are used to combat pests of plants.
Conclusion
So, acetic acid (CH3COOH), a colorless combustible liquid with a sharp smell, well soluble in water. It has a characteristic sour taste, electric current conducts. The use of acetic acid in the industry is very large.
Acetic acid produced in Russia is at the level of the best world standards, is in high demand in the world market and is exported to many countries of the world.
The production of acetic acid has a number of its specific requirements, therefore specialists are needed, which have a wide experience not only in the field of automation and process management and proceedings, but also clearly understand the special requirements of this industry.
List of used literature
1. Artemenko, Alexander Ivanovich. Reference Guide for Chemistry / A.I. Artyomenko, I.V. Tikunova, V.A. Male. - 2nd ed., Pererab. and add. - M.: high school, 2002. - 367 with
2. Akhmetov, Nail Sibgatovich. General and inorganic chemistry: textbook for stud. Him.-tehnol. specialist. universities / Akhmetov N.S.-4th ed. / University - M.: Higher School, 2002.-743 p.
3. Berezin, Boris Dmitrievich. The course of modern organic chemistry: studies. Manual for studies universities, leisure. In Him.-Tehnol. Spec. / Berezin B.D., Berezin D. B.-M.: Higher School, 2001.-768 p.
4. I. G. Bolsheov, G. S. Zaitseva. Carboxylic acids and their derivatives (synthesis, reactivity, application in organic synthesis). Methodological materials at the general course of organic chemistry. Issue 5. Moscow 1997
5. Zommer K. Battery Knowledge of Chemistry. Per. With him., 2nd ed. - M.: Mir, 1985. - 294 p.
6. Karakhanov E.A. Synthesis gas as an alternative to oil. I. Fischer-Tropsch process and oxo-synthesis // Syrian educational magazine. 1997. No. 3. P. 69-74.
7. Karavaev M.M., Leonov E.V., Popov I.G., Shepelev E.T. Technology of synthetic methanol. M., 1984. 239 p.
8. Catalysis in C1 chemistry / ed. V. Kima. M., 1983. 296 p.
9. Reutov, Oleg Aleksandrovich. Organic Chemistry: Tutorial for stud. universities, leisure. for example and special. "Chemistry" / Reutov O.A., Kurtz A.L. Butin K.P.-M.: Publishing House of Moscow State University.-21 See Ch. 1.-1999.-560 p.
10. Soviet Encyclopedic Dictionary, Ch. ed. A.M. Prokhorov - Moscow, Soviet Encyclopedia, 1989
11. Chemistry: Reference Guide, Ch. ed. N.R. Lieberman - St. Petersburg, Publishing House "Chemistry", 1975
12. Chemistry: Organic Chemistry: Training Edition for 10 CL. environments shk. - Moscow, Enlightenment, 1993
Sommer K. Knowledge Battery in Chemistry. Per. With him., 2nd ed. - M.: Mir, 1985. P. 199.
I. G. Bolsheov, G. S. Zaitseva. Carboxylic acids and their derivatives (synthesis, reactivity, application in organic synthesis). Methodological materials at the general course of organic chemistry. Issue 5. Moscow 1997 P. 23
Sommer K. Knowledge Battery in Chemistry. Per. With him., 2nd ed. - M.: Mir, 1985. P. 201
Karakhanov E.A. Synthesis gas as an alternative to oil. I. Fischer-Tropsch process and oxo-synthesis // Syrian educational magazine. 1997. No. 3. P. 69
Sommer K. Knowledge Battery in Chemistry. Per. With him., 2nd ed. - M.: Mir, 1985. P. 258.
Sommer K. Knowledge Battery in Chemistry. Per. With him., 2nd ed. - M.: Mir, 1985. P. 264
Acetic acid (ACETIC ACID, etching acid, E260) is weak, limiting monosular carboxylic acid.
Acetic acid is a colorless liquid with a characteristic sharp odor and sour taste. Hygroscopic. Unlimited soluble in water. Chemical formula CH3COOH.
70-80% aqueous solution of acetic acid is called acetic essence, and 3-6% - vinegar. Aqueous acetic acid solutions are widely used in the food industry and household cooking, as well as in conservation.
Product of a natural whiskey of grape dry wines and fermentation of alcohols and carbohydrates. Participates in the metabolism in the body. Widely used in the preparation of canned food, marinades, vinegarets.
Acetic acid is used to obtain medicinal and fragrant substances, as a solvent (for example, in the production of acetylcellulose, acetone). It is used in typography and collapse.
Salts and acetic esters are called acetates.
Food additive E260 is known as acetic acid or vinegar. E260 additive is used in the food industry as an acidity regulator. Basically, acetic acid is used in the form of aqueous solutions in the proportion of 3-9% (vinegar) and 70-80% (acetic essence). E260 additive has a characteristic sharp smell. In aqueous solutions, the E260 acidity regulator is rather weak acid. In the purest form, acetic acid is a colorless caustic liquid absorbed by moisture from the environment and freezing already at a temperature of 16.5 ° C with the formation of solid colorless crystals. Chemical formula of acetic acid: C 2 H 4 O 2.
Vinegar was known for several more millennia ago, as a natural fermentation product of beer or wine. In 1847, the German chemist Herman Kolbe first synthesized acetic acid in laboratory conditions. Now in the world, only 10% of the total production of acetic acid is produced. But the natural method of fermentation is still important, as in many countries there are laws, according to which only acetic acid of biological origin should be used in the food industry. When biochemical production, E260 additives uses the ability of some bacteria to oxidize ethanol (alcohol). This method is known as acetic fermentation. As a raw material for the production of E260 supplements, born juices, wine or alcohol solution in water are used. There are also a number of acetic acid synthesis methods in industry. The most popular of them, which accounts for more than half of the global acetic synthesis, is to carbonylation of methanol in the presence of catalysts. The initial components for this reaction are methanol (CH 3 OH) and carbon monoxide (CO).
Acetic acid is important for the work of the human body. Its derivatives helps to split carbohydrates and fats in the body entering the body with food. Acetic acid stands out in the vital activity of certain types of bacteria, in particular Clostridium Acetobutylicum and bacteria Roda Acetobacter.. These bacteria are found everywhere in water, soil, food products and naturally fall into the human body.
The toxic effect of the E260 additive to the human body depends on the degree of dilution of acetic acid with water. Dangerous to health and life is considered solutions in which the concentration of acetic acid is above 30%. Highly concentrated acetic acid when contacting leather and mucous membranes can cause strong chemical burns.
In the food industry, the E260 supplement is used to baking confectionery, canning vegetables, mayonnaise production and other food products.
The E260 acidity regulator is allowed for use in food in all countries, as an additive safe for human health.
Acetic acid is also used:
- in everyday life (removal of scale from kettles, care for surfaces);
- in the chemical industry (as a solvent and chemical agent);
- in medicine (preparation of medicines);
- in other industries.
Food preservative E260 acetic acid is well-known to all people who are interested in the art of gastronomy. This product is the result of the whisening of grape wines in vivo, in which the alcohol and carbohydrates are fermented. In addition, it is known that acetic acid is directly involved in the process of metabolism in the human body.
Acetic acid is inherent in a sharp smell, but in its pure form it is a completely colorless liquid capable of absorbing moisture from the environment. This substance can be freezing at a temperature of minus 16 degrees, as a result forming transparent crystals.
It is noteworthy that a vinegar is called a 3-6% solution of acetic acid, while at 70-80 percentage contains acetic essence. Water-based E260 solutions are widely used not only in the food industry, but also in household cooking. The main use of food preservative E260 acetic acid is the manufacture of marinades and canned food.
In addition, this substance is actively added and in the industrial production of a number of confectionery products, as well as mayonnaise and canned vegetables. Often, with particular need for food preservative E260 acetic acid can be applied as a disinfectant and disinfection agent.
However, the product of food production is not the only sphere of use of the food preservative E260. Thus, it is widely used in chemical production when producing organic glass, acetate fiber, as well as in the manufacture of ethers and medicines.
By the way, the so-called acetic ether is widely used in pharmacology, which is more famous for a person called acetylsalicylic acid or aspirin. As a solvent, acetic acid also helps people in some cases, and the salt allocated from its composition is successfully used in the fight against pests of plants.
Harm of Food Preservative E260 Acetic Acid
Harm of food preservative E260 acetic acid for man is especially evident with the use of this substance in high concentrations, as in this form it is very toxic. By the way, the degree of toxicity of acid directly depends on how much it was diluted with water. Solutions are considered the most dangerous health, the concentration of which exceeds 30 percent. When contacting mucous membranes or leather with concentrated acetic acid, the strongest chemical burns arise.
Food Preservative E260 Acetic acid is allowed for use in the food industry in all countries of the world, as it is not considered dangerous to health. The only thing experts are recommended to avoid probable harm of the food preservative E260 acetic acid - to limit the use of products with this substance in the composition of people with liver diseases and the gastrointestinal tract. Such products do not advise to give children under 6-7 years.
The usual bottle of food vinegar, which can be found in the kitchen in any housewife, has many other acids and vitamins. Adding a pair of product droplets into the cooked food, salads cause a natural intensity of taste. But few of us seriously thought about the properties and the real scale of the application of the main component - acetic acid.
What is this substance?
The formula of acetic acid CH 3 of the coxy, which relates it to a row of fatty carboxylic acids. The presence of one carboxyl group (SON) refers it to monosocond acids. The substance occurs on the globe in organic form and is obtained by synthetic in laboratories. Acid is the easiest, but no less important representative of his row. Easily dissolved in water, hygroscopic.
The physical properties of acetic acid and the density change depending on the temperature regime. At room temperature in 20 o C acid, it is in a liquid state, has a density of 1.05 g / cm 3. It has a specific smell and sour taste. The solution of the substance without impurities is hardening and passes into the crystals at a temperature below 17 o C. The boiling process of acetic acid begins at a temperature of above 117 o C. Metyl group (CH 3) of acetic acid formulas is obtained by interacting with oxygen alcohols: fermentation of alcohol and carbohydrates, Skin wines.
A bit of history
The opening of the vinegar was one of the first in the row of acids and was accomplished in stages. Initially, acetic acid began to produce by distillation Arabic scientists of the 8th century. However, in ancient Rome, this substance obtained from the skysheld wine was used as a universal sauce. The name itself with ancient Greek is translated as "sour". In the 17th century, scientists of Europe managed to produce a pure substance substance. At that time, they brought the formula and found an unusual ability - Acetic acid in a vapor state flammed with blue fire.
Until the 19th century, scientists found the presence of acetic acid only in organic form - as part of salts and ether compounds. As part of plants and their fruits: apples, grapes. In the body of people and animals: sweat selection, bile. At the beginning of the 20th century, Russian scientists randomly produced acetic aldehyde from the acetylene reaction with mercury oxide. Today, the consumption of acetic acid is so large that its main production occurs only with a synthetic way in a huge scale.
Methods of production
Will there be acetic acid of a pure form or with the presence of impurities in the solution Depends on the mining method. Food acetic acid is obtained by a biochemical method in the process of ethanol fermentation. In industry, several acid production methods are isolated. As a rule, reactions are accompanied by high temperatures and the presence of catalysts:
- Methanol in the carbon reaction (carbonylation).
- Oxidation of oil fraction oxygen.
- Pyrolysis of wood.
- oxygen.
Industrial method is more efficient and more economical biochemical. Thanks to the industrial method, the volume of hydrocarbon acid production in the 20th and 21st century increased hundreds of times, compared with the 19th century. Today, the synthesis of acetic acid is carbonylation of methanol gives a 50% of the total volume produced.
Physical properties of acetic acid and its effect on the indicator
In a liquid state, acetic acid is colorless. The level of acidity pH 2.4 is easily checked with a litmus paper. Acetic acid when hitting the indicator stains it in red. The physical properties of acetic acid change visually. When the temperature drops below 16 o C, the substance takes a solid shape and resembles minor ice crystals. It is easily dissolved in water and interacts with a wide range of solvents, except hydrogen sulfide. Acetic acid reduces the total volume of fluid when it diluted with water. We independently describe the physical properties of acetic acid, its color and consistency that you observe in the following image.
The substance flammives at a temperature of from 455 ° C with heat release in 876 kJ / mol. The molar mass is 60.05 g / mol. The physical properties of acetic acid as an electrolyte in reactions appear weakly. The dielectric constant is 6.15 at room temperature. Pressure, like density, - The variable magnitude of the physical properties of acetic acid. With a pressure of 40 mm. RT. Art. and the temperature of the boiling process 42 o C will begin. But already at a pressure of 100 mm. RT. Art. Boiling will occur only at 62 o C.
Chemical properties
Entering the reaction with metals and oxides, the substance exhibits its acidic properties. Perfectly dissolving more complex compounds, acid forms salts that are called acetates: magnesium, lead, potassium, etc. PK acid is 4.75.
When interacting with gases, vinegar enters, followed by the displacement and formation of more complex acids: chlororacus, iodoacetic. Dissolving in water, the acid dissociates with the release of acetate ions and hydrogen protons. The degree of dissociation is 0.4 percent.
The physical and chemical properties of acetic acid molecules in crystalline form form diamers on hydrogen bonds. Its properties are also necessary when creating more complex fatty acids, steroids and biosynthesis of sterols.
Laboratory tests
Detect acetic acid in solution by identifying its physical properties, such as smell. It is enough to add stronger acid to the solution, which will begin to force out the salt of vinegar with the highlight of its vapors. By laboratory distillation CH 3 Coona and H 2 SO 4, it is possible to obtain acetic acid in a dry form.
We will experience experience from the school curriculum of grade 8. The physical properties of acetic acid brightly demonstrates the chemical response of the disposal. It is enough to add to the solution to the substance of copper oxide and heat it slightly. The oxide is completely dissolved, making a solution of bluish color.
Derived substances
Qualitative reactions of the substance with many solutions form: ethers, amides and salts. However, during the production of other substances, the requirements for the physical properties of acetic acid remain high. It should always have a high degree of dissolution, which means not to have third-party impurities.
Depending on the concentration of acetic acid aqueous solution, a number of its derivatives are distinguished. The concentration of the substance is more than 96% is called icy acetic acid. Acetic acid in 70-80% can be purchased at grocery stores, it will be called - Acetic essence. Table vinegar has a concentration of 3-9%.
Acetic acid and everyday life
In addition to food features, acetic acid has a number of physical properties, which humanity has found its use in everyday life. The solution of the substance of a low concentration easily removes the flare from the metal products, the surface of the mirrors and windows. The ability to absorb moisture also plays benefit. Vinegar is well eliminating smells in the stale premises, removes stains from vegetables and fruits on clothes.
As it turned out, the physical property of acetic acid - Eliminate fat from the surface - can be used in folk medicine and cosmetology. A weak solution of food vinegar process hair to give them glitter. The substance is widely used to treat colds, removing warts and skin fungi. Picks the pace the use of vinegar as part of cosmetic wraps to combat cellulite.
Use in production
In salts and other complex substances, acetic acid performs an indispensable element:
- Pharmaceutical industry. To create: aspirin, antiseptic and antibacterial ointments, fenacetin.
- Production of synthetic fibers. Non-combustible films, acetylcellulose.
- Food industry. For successful conservation, making marinades and sauces, as a food additive E260.
- Textile industry. Included in the dyes.
- Production of cosmetics and hygiene products. Aromatic oils, cream to improve skin tone.
- Making a dory. Used as insecticide and rubbing from weeds.
- Production of varnishes. Technical solvents, production of acetone.
Annually, the production of acetic acid increases. Today, its volume in the world is more than 400 thousand tons per month. Acid transportation is carried out in durable steel tanks. Storage in plastic containers in many industries due to the high physical and chemical activity of acetic acid is prohibited either limited to a period of up to several months.
Security
High concentration acetic acid has a third degree of ignition and highlights toxic pairs. It is recommended to wear special gas masks and other personal protective equipment in the process of working with acid. Mortal dose for the human body from 20 ml. At the time of entering the substance inside the acid, first of all burns the mucous membrane, and then affects the remaining organs. In such cases, immediate hospitalization is needed.
After entering the acid to open areas, it is recommended to rinse them immediately with running water. Superficial rehabilitation can cause tissue necrosis, which also requires hospitalization.
Scientists of physiology found out that the person is not required to receive acetic acid at all - without food additives you can do. But people with intolerance to acid, as well as with the problems of the stomach, the substance is contraindicated.
Acetic acid is used in typography.
The substance in a small amount was found in honey, bananas and wheat.
By cooling the acetic acid and having sharply stalking with it the container, it is possible to observe its sharp frost.
A small concentration of acetic acid can reduce pain symptom from the bite of insects, as well as small burns.
Admission to food products with a small content of acetic acid reduces cholesterol levels in the body. The substance well stabilizes the level of sugar from diabetics.
The use of protein and carbohydrate food together with a small amount of acetic acid increases their digestibility by the body.
If the food is saved, it is enough to add a couple of vinegar drops to smooth out the brassiness.
Finally
The millennium of using acetic acid led to the fact that its physical and chemical properties are used at each step. Hundreds of possible reactions, thousands of useful substances, thanks to which humanity goes on. The main thing is to know all the features of acetic acid, its positive and negative qualities.
Do not forget about benefits, but it should always be remembered what harm can cause a careless handling of high concentration acetic acid. By its danger, she stands next to the salt and always remember the safety technique when using acid. Right and carefully dilute the essence of water.