Preparation of carboxylic acids

I. In industry

1. Isolated from natural products

(fats, waxes, essential and vegetable oils)

2. Oxidation of alkanes:

2CH 4 + + 3O 2 t,kat→ 2HCOOH + 2H 2 O

methaneformic acid

2CH 3 -CH 2 -CH 2 -CH 3 + 5O 2 t,kat,p→4CH 3 COOH + 2H 2 O

n-butaneacetic acid

3. Oxidation of alkenes:

CH 2 =CH 2 + O 2 t,kat→CH3COOH

ethylene

WITH H 3 -CH=CH 2 + 4[O] t,kat→ CH 3 COOH + HCOOH (acetic acid + formic acid )

4. Oxidation of benzene homologues (production of benzoic acid):

C 6 H 5 -C n H 2n+1 + 3n[O] KMnO4,H+→ C 6 H 5 -COOH + (n-1)CO 2 + nH 2 O

5C 6 H 5 -CH 3 + 6KMnO 4 + 9H 2 SO 4 → 5C 6 H 5 -COOH + 3K 2 SO 4 + 6MnSO 4 + 14H 2 O

toluenebenzoic acid

5.Receipt formic acid:

Stage 1: CO+NaOH t , p→HCOONa (sodium formate – salt )

2 stage: HCOONa + H 2 SO 4 → HCOOH + NaHSO 4

6. Preparation of acetic acid:

CH3OH+CO t,p→CH3COOH

Methanol

II. In the laboratory

1. Hydrolysis of esters:

2. From salts of carboxylic acids :

R-COONa + HCl → R-COOH + NaCl

3. Dissolving carboxylic acid anhydrides in water:

(R-CO) 2 O + H 2 O → 2 R-COOH

4. Alkaline hydrolysis of halogen derivatives of carboxylic acids:

III. General methods for preparing carboxylic acids

1. Oxidation of aldehydes:

R-COH + [O] → R-COOH

For example, the “Silver Mirror” reaction or oxidation with copper (II) hydroxide are qualitative reactions of aldehydes

2. Oxidation of alcohols:

R-CH 2 -OH + 2[O] t,kat→ R-COOH + H 2 O

3. Hydrolysis of halogenated hydrocarbons containing three halogen atoms per carbon atom.

4. From cyanides (nitriles) - the method allows you to increase the carbon chain:

WITH H 3 -Br + Na-C≡N → CH 3 -CN + NaBr

CH3-CN - methyl cyanide (acetic acid nitrile)

WITH H 3 -CN + 2H 2 O t→ CH 3 COONH 4

acetate ammonium

CH 3 COONH 4 + HCl → CH 3 COOH + NH 4 Cl

5. Usage reagent Grignard

R-MgBr + CO 2 →R-COO-MgBr H2O→ R-COOH + Mg(OH)Br

APPLICATION OF CARBOXYLIC ACIDS

Formic acid– in medicine - formic alcohol (1.25% alcohol solution of formic acid), in beekeeping, in organic synthesis, in the production of solvents and preservatives; as a strong reducing agent.

Acetic acid– in the food and chemical industries (production of cellulose acetate, from which acetate fiber, organic glass, film are produced; for the synthesis of dyes, medicines and esters). IN household as a flavoring and preservative substance.

Butyric acid– for the production of flavoring additives, plasticizers and flotation reagents.

Oxalic acid– in the metallurgical industry (descaling).

Stearic C17H35COOH and palmitic acid C 15 H 31 COOH – as surfactants, lubricants in metalworking.

Oleic acid C 17 H 33 COOH is a flotation reagent and collector for the enrichment of non-ferrous metal ores.

Individual representatives

monobasic saturated carboxylic acids

Formic acid was first isolated in the 17th century from red forest ants. Also found in stinging nettle juice. Anhydrous formic acid is a colorless liquid with a pungent odor and pungent taste that causes burns on the skin. It is used in the textile industry as a mordant for dyeing fabrics, for tanning leather, and also for various syntheses.
Acetic acid widespread in nature - found in animal excretions (urine, bile, feces), in plants (in green leaves). It is formed during fermentation, rotting, souring of wine, beer, and is found in sour milk and cheese. The melting point of anhydrous acetic acid is + 16.5°C, its crystals are transparent as ice, which is why it is called glacial acetic acid. It was first obtained at the end of the 18th century by the Russian scientist T. E. Lovitz. Natural vinegar contains about 5% acetic acid. Vinegar essence is prepared from it, used in the food industry for preserving vegetables, mushrooms, and fish. Acetic acid is widely used in the chemical industry for various syntheses.

Representatives of aromatic and unsaturated carboxylic acids

Benzoic acid C 6 H 5 COOH is the most important representative of aromatic acids. Distributed in nature in flora: in balms, incense, essential oils. In animal organisms it is found in the breakdown products of protein substances. This crystalline substance, melting point 122°C, easily sublimes. IN cold water does not dissolve well. It dissolves well in alcohol and ether.

Unsaturated unsaturated acids with one double bond in the molecule have the general formula C n H 2 n -1 COOH.

High molecular weight unsaturated acids often mentioned by nutritionists (they call them unsaturated). The most common of them is oleic CH 3 –(CH 2) 7 –CH=CH–(CH 2) 7 –COOH or C 17 H 33 COOH. It is a colorless liquid that hardens in the cold.
Polyunsaturated acids with several double bonds are especially important: linoleic CH 3 –(CH 2) 4 –(CH=CH–CH 2) 2 –(CH 2) 6 –COOH or C 17 H 31 COOH with two double bonds, linolenic CH 3 –CH 2 –(CH=CH–CH 2) 3 –(CH 2) 6 –COOH or C 17 H 29 COOH with three double bonds and arachidonic CH 3 –(CH 2) 4 –(CH=CH–CH 2) 4 –(CH 2) 2 –COOH with four double bonds; they are often called essential fatty acids. It is these acids that have the greatest biological activity: they participate in the transfer and metabolism of cholesterol, the synthesis of prostaglandins and other vital substances, and maintain the structure cell membranes, are necessary for the functioning of the visual apparatus and nervous system, affect the immune system. The absence of these acids in food inhibits the growth of animals, inhibits their reproductive function, and causes various diseases. The human body cannot synthesize linoleic and linolenic acids itself and must receive them ready-made with food (like vitamins). For the synthesis of arachidonic acid in the body, linoleic acid is necessary. Polyunsaturated fatty acids with 18 carbon atoms in the form of glycerol esters are found in the so-called drying oils - flaxseed, hemp, poppy, etc. Linoleic acid C17H31COOH and linolenic acid C 17 H 29 COOH are part of vegetable oils. For example, linseed oil contains about 25% linoleic acid and up to 58% linolenic acid.

Sorbic acid (2,4-hexadienoic) acid CH 3 –CH=CH–CH=CHCOOH was obtained from rowan berries (sorbus in Latin). This acid is an excellent preservative, so rowan berries do not become moldy.

The simplest unsaturated acid, acrylic CH 2 = CHCOOH, has a pungent odor (in Latin acris - pungent, pungent). Acrylates (esters of acrylic acid) are used to produce organic glass, and its nitrile (acrylonitrile) is used to produce synthetic fibers.

When naming newly isolated acids, chemists often give free rein to their imagination. Thus, the name of the closest homolog of acrylic acid, croton

CH 3 – CH = CH – COOH, does not come from a mole at all, but from a plant Croton tiglium, from whose oil it was isolated. The synthetic isomer of crotonic acid is very important - methacrylic acid CH 2 = C (CH 3) – COOH, from the ester of which (methyl methacrylate), as well as from methyl acrylate, transparent plastic is made - plexiglass.

Unsaturated carbon acids are capable of addition reactions:

CH 2 = CH-COOH + H 2 → CH 3 -CH 2 -COOH

CH 2 =CH-COOH + Cl 2 → CH 2 Cl -CHCl -COOH

VIDEO:

CH 2 =CH-COOH + HCl → CH 2 Cl -CH 2 -COOH

CH 2 = CH-COOH + H 2 O → HO-CH 2 -CH 2 -COOH

The last two reactions proceed against Markovnikov's rule.

Unsaturated carboxylic acids and their derivatives are capable of polymerization reactions.

In 1670, the English botanist and zoologist John Ray (1627-1705) conducted an unusual experiment. He placed red forest ants in a vessel, poured in water, heated it to a boil and passed a stream of hot steam through the vessel. This process is called steam distillation by chemists and is widely used to isolate and purify many organic compounds. After the steam condensed, Rey obtained an aqueous solution of a new chemical compound. It exhibited, and therefore was called formic acid (the modern name is methane). The names of salts and esters of methane acid - formates - are also associated with ants (Latin formica - “ant”).

Subsequently, entomologists - insect specialists (from the Greek “entokon” - “insect” and “logos” - “teaching”, “word”) determined that females and working ants have poisonous glands in their abdomens that produce acid. The forest ant has approximately 5 mg. Acid serves as an insect weapon for defense and attack. There is hardly a person who has not experienced their bites. The sensation is very reminiscent of a nettle burn, because formic acid is also contained in the finest hairs of this plant. Sticking into the skin, they break off, and their contents burn painfully.

Formic acid is also found in bee venom, pine needles, silkworm caterpillars, and in small quantities it is found in various fruits, organs, tissues, and animal and human secretions. In the 19th century formic acid (in the form of sodium salt) was obtained artificially by the action of carbon monoxide (II) on wet elevated temperature: NaOH + CO = HCOONa. Conversely, under the influence of concentrated formic acid, it decomposes with the release of gas: HCOOH = CO + H 2 O. This reaction is used in the laboratory to obtain pure. When the sodium salt of formic acid - sodium formate - is strongly heated, a completely different reaction occurs: the carbon atoms of two acid molecules seem to be cross-linked and sodium oxalate is formed - a salt of oxalic acid: 2HCOONa = NaOOC-COONa + H 2.

An important difference between formic acid and others is that it, like a two-faced Janus, has both the properties of both an acid and a a carbon atom that is part of the aldehyde group H-CO-. Therefore, formic acid reduces silver from its solutions - it gives a “silver mirror” reaction, which is characteristic of aldehydes, but not characteristic of acids. In the case of formic acid, this reaction, which is also unusual, is accompanied by the release of carbon dioxide as a result of the oxidation of organic acid (formic) to inorganic acid (carbonic), which is unstable and decomposes: HCOOH + [O] = HO-CO-OH = CO 2 + H 2 O.

Formic acid is the simplest and at the same time the strongest carboxylic acid; it is ten times stronger than acetic acid. When the German chemist Justus Liebig first obtained anhydrous formic acid, it turned out that this was a very dangerous compound. When it comes into contact with the skin, it not only burns, but also literally dissolves it, leaving wounds that are difficult to heal. As Liebig's collaborator Karl Vogt (1817-1895) recalled, he had a scar on his hand for the rest of his life - the result of an “experiment” conducted jointly with Liebig. And it is not surprising - it was later discovered that anhydrous formic acid even dissolves nylon, nylon and other polymers that do not take diluted solutions of other acids and alkalis.

Formic acid found an unexpected application in the production of so-called heavy liquids - aqueous solutions in which even stones do not sink. Geologists need such liquids to separate minerals by density. By dissolving the metal in a 90% solution of formic acid, thallium formate HCOOTl is obtained. This solid salt may not hold a record for density, but it is distinguished by exceptionally high solubility: in 100 g of water at room temperature you can dissolve 0.5 kg (!) of thallium formate. For a saturated aqueous solution, the density varies from 3.40 g/cm 3 (at 20 o C) to 4.76 g/cm 3 (at 90 o C). The solution of a mixture of thallium formate and thallium malonate, the salt of malonic acid CH 2 (COOTl) 2, has an even greater density.

When these are dissolved (in a 1:1 ratio by weight) in minimum quantity water, a liquid with a unique density is formed: 4.324 g/cm 3 at 20 o C, and at 95 o C the density of the solution can be increased to 5.0 g/cm 3. Barite (heavy spar), quartz, corundum, malachite and even granite float in such a solution!

Formic acid has strong bactericidal properties. Therefore, its aqueous solutions are used as a food preservative, and in pairs they disinfect food containers (including wine barrels) and destroy bee mites. A weak aqueous-alcohol solution of formic acid (formic alcohol) is used in medicine for rubbing.

Formic acid is a monobasic carboxylic acid registered as a food additive with code E236 according to the international classification, which is used as a preservative. It is considered the first representative in the series of saturated monobasic carboxylic acids.

Chemical formula HCOOH.

General characteristics of Formic acid

Formic acid is a clear, colorless, odorless, and sour taste. The substance has the property of dissolving in glycerin, benzene and acetone and miscible with water and ethanol. Formic acid was named after the Englishman John Ray isolated it from a huge number of red forest ants (calorizator). Chemically produced as a by-product of synthesis. Natural suppliers of formic acid are pine needles, and excretions of bees and ants.

Useful properties of Formic acid

Basics useful property formic acid - slowing down the processes of decay and rotting, respectively, increasing the shelf life and use of products. It has been noted that formic acid stimulates cell metabolism and is an irritant to nerve endings.

Harm E236

Food additive E236 Formic acid can cause allergic reactions and serious disorders gastrointestinal tract in case of overdose. If formic acid in its pure form gets on the skin or mucous membranes, as a rule, a burn occurs, which must be treated as quickly as possible with a solution and immediately contact a medical facility for qualified help.

Contact with concentrated formic acid vapor may cause damage to the eyes and respiratory tract. Accidental ingestion of even diluted solutions causes severe necrotizing gastroenteritis.

The danger of formic acid depends on the concentration. According to classification European Union, a concentration of up to 10% has an irritating effect, more than 10% has a corrosive effect.

Application of E236

The food additive E236 is most often used as an antibacterial and preservative agent in the production of livestock feed. In the food industry, the properties of E236 are used in confectionery, non-alcoholic and alcoholic drinks, canned fish and meat. Formic acid is also used in the chemical industry, medicine and pharmaceuticals, in the production of woolen fabrics and leather tanning.

Use of E236 in Russia

In the territory Russian Federation the use of food additive E236 as a neutral preservative is permitted, subject to compliance with the standards established Sanitary rules RF.

In the 17th century, it was found in ants and decided to be called formic. insects excrete when bitten.

John Rayem, who discovered the compound, studied red ants. With their help I obtained the reagent.

Later, it turned out that formic acid not at all antlike, or rather, not only.

The substance is found in fruits, plants, human sweat, and urine. In addition to ants, bees also produce stings.

So, everyone will remember the feeling of getting into it. It's a burning sensation. Although the reagent is not considered strong, it is still.

The class name is justified. All its compounds taste sour. But not now general properties, but the characteristics of the ant reagent.

Properties of formic acid

HCOOH is formic acid formula. COOH is called a carboxyl group by chemists.

In the heroine she is alone, therefore, the connection is monobasic. CH 4 – methane. Accordingly, methane.

Putting the data together, we get a monobasic carbonic methane compound. It is biogenic because it is produced by living organisms, and not just synthesized.

The chain of molecules is open. If it reacts with alcohol, an esterified form of the compound will be obtained.

This is typical for oils, waxes, in general, vegetable and fats. Therefore, methane is called fatty.

However, in its series the compound stands apart, since the carboxyl group is attached to.

Usually, it comes into contact with an alkyl, that is, a hydrocarbon radical. As a result, the heroine of the article can be classified not only as fatty acids, but also as aldehydes, and simply as alcohols.

Like them, formic acid is capable of oxidizing. The result of the reaction is acid.

From aldehydes, the compound also acquired the ability to reduce mercury oxides. Formic acid reactions go with them when heated.

The result is nitrous oxide, and sometimes its metallic form. A similar reaction occurs with.

Interaction gives formic acid salt. It simply decomposes, again yielding pure argentum.

Antweed does not have a crystalline state. The compound is initially liquid and easily mixed with acetone, glycerin, and benzene.

The latter substances are aromatic. Formic acid also has an odor. The aroma is specific, sharp.

In aqueous solutions of the compound, it dissipates as the acid concentration decreases. The smell is pungent only in its anhydrous form.

Although, water may be found in it. You just need to mix sulfuric acid with formic acid. The result of the reaction is carbon monoxide and water.

The latter is used for household needs. But carbon monoxide is a product needed to create synthetic liquid fuels, organic acids, and alcohols.

Carbon dioxide can also be obtained from formic acid. The heroine of the article disintegrates into it and hydrogen in the presence of two metals - and.

One of them is enough for a reaction. Speaking in simple language, carbon dioxide is carbon monoxide.

However, industrialists also need it. The compound is added to sodas, and.

It remains to find out why you need it yourself formic acid. Reviews industrialists, and not only, further.

Applications of formic acid

Application The compound was found in the food industry. If you see E236 on the package, you know this formic acid. Buy They offer drinks with it, both non-alcoholic and alcoholic, for example, wine.

E236 is also added to animal feed and canned vegetables. Accordingly, the additive helps products last longer. Conclusion: - the reagent has antibacterial properties.

In organism formic acid solution does not linger, is quickly removed. The main thing is not to overdo it.

If the compound concentrate accidentally gets on the skin or inside, burns, poisoning, and loss of vision cannot be avoided.

Animals are also offered products containing formic acid. It's no longer about pets and their food.

Ant compounds are also added to hay and silage for livestock. Acid slows down the decay process. The decomposition of hay slows down, it remains healthy and tasty until spring.

Formic acid in pharmacies It is sold not only as a disinfectant, but also as a medicine for varicose veins.

Getting into small quantities, the reagent promotes vasodilation, and therefore improves blood flow.

This serves to prevent blood clots - fatal dangerous consequences varicose veins

Blood stagnates in the veins, and clots form that attach to the walls of the vessels. Breaking away, they rush to the heart.

If they reach it, instant death will follow. The problem, as you can see, is acute and no less “acute” can help solve it. agent – ​​formic acid.

Doctors also use methanoic acid as an immunostimulant. The compound plays this role in the treatment of tuberculosis.

The reagent is also capable of fighting fungal diseases. Although, some of the pharmaceutical products are more cosmetic-oriented.

So, based on the heroine of the article, acne remedies are made. You can also buy cream with formic acid.

It is usually taken for solariums. The product is slightly irritating and therefore warms the skin.

Eventually, metabolic processes proceed faster, the integument seems to attract ultraviolet radiation.

So, formic acid for tanning allows you to reduce the time you spend in the solarium, while still getting the desired effect.

In the chemical industry, formic acid serves as a reducing agent. Properties borrowed from aldehydes help.

The reagent is also needed in the textile industry for dyeing fabrics. Formic acid acts as a mordant.

It is needed to prepare the surface of the material, otherwise the dye will lie unevenly.

Interestingly, formic acid is also used outside of human society.

So, after hibernation, bears go to anthills and lie down on them. Giants bear no grudge against insects.

Formic acid extraction

Preparation of formic acid- a road that branches. There are several ways to obtain the reagent.

First - formic acid production from carbon compounds, for example, chloroform. It is exposed to diluted alkali.

It is also possible to saponify hydrocyanic acid, react with carbon dioxide on hydrite, and heat oxalic acid in the presence of glycerin.

However, industrialists use only one method. This is the passage of carbon monoxide through caustic soda.

An aqueous solution of the reagent can be obtained by distilling formic acid and sulfuric acid.

If you need to remove water, use oxalic acid concentrate. The usual fractional distillation of aqueous solutions will not help.

At 107 degrees, a mixture of methane acid and water is a constantly boiling composition. Moreover, the heroine of the article is only 77%.

Formic acid price

On formic acid price depends mainly on concentration. Most often, they sell solutions rather than a dehydrated reagent.

For medical purposes, for example, a concentration of only 1.4% is needed. The drug is called formic alcohol and costs about 20 rubles for a 50-ml bottle.

If additional components are added to the compound, for example, body care, the price will be different. So, a 75-ml bottle of skin balm can cost 110, or even 200 rubles.

For industrialists, the reagent is shipped in tanks or canisters of 25 and 35 kilograms. For the latter, they ask for around 3000-4000 rubles.

The price per kilo is 50-150 rubles. These are seller requests for 85 percent acid.

The price range is related to the purity of the connection and the personal ambitions of businessmen, as well as the place of production.

The most profitable products are from and domestic samples. The price is partly affected by packaging. It can be metal or plastic.

The presence of a convenient drain, like canisters, is taken into account. As a rule, this is not the case in barrels. There are a number of containers that, once opened, cannot be closed.

For this inconvenience, the price is slightly reduced. They also reduce it for wholesalers. For large orders you can save from 5 to 20, and sometimes even 25%.

The attitude towards regular partners is especially loyal. To some of them, acid is shipped even without prepayment.

Methane boiler.

Chemical properties

Chemical formula of formic acid: HCOOH. This is one of the first representatives of single-base carbon compounds. The substance was first isolated in 1670 from the forest (red) ant. IN natural environment found in bee venom, nettles and needles coniferous trees, jellyfish secretions, fruits.

Physical properties

Racemic formula of methanoic acid: CH2O2. Substance at normal conditions has the appearance of a colorless liquid that is highly soluble in, acetone , toluene And benzene . Molar mass = 46.02 grams per mole. Esters (ethyl ether and methyl ether) and methane salts are called formates .

Chemical properties

Based on the structural formula of Formic acid, we can draw conclusions about its chemical properties. Formic acid is capable of exhibiting properties of the kit and some of the properties of aldehydes (reduction reactions).

When formic acid is oxidized, for example, carbon dioxide is actively released. The substance is used as a preservative agent (code E236). Formic acid reacts with acetic acid (concentrated) and decomposes into carbon monoxide and ordinary water with the release of heat. A chemical compound reacts with sodium hydroxide . The substance does not interact with hydrochloric acid, silver, sodium sulfate and so on.

Preparation of formic acid

The substance is formed as a by-product during oxidation butane and production vinegar . It can also be obtained by hydrolysis formamide And methyl formate (with excess water); during the hydration of CO in the presence of any alkali. Qualitative reaction for detection methanoic acid may be a reaction to algedigs . The role of an oxidizing agent can be ammonia solution of silver oxide and Cu(OH)2. The silver mirror reaction is used.

Applications of formic acid

The substance is used as an antibacterial agent and preservative when preparing feed for long-term storage; the product significantly slows down the processes of decay and rotting. The chemical compound is used in the process of dyeing wool; as an insecticide in beekeeping; during certain chemical reactions (acts as a solvent). In the food industry, the product is labeled E236. In medicine, acid is used in combination with (“pervomur” or performic acid ) as antiseptic , for the treatment of joint diseases.

pharmachologic effect

Local anesthetic, distracting, anti-inflammatory, local irritating, improving tissue metabolism.

Pharmacodynamics and pharmacokinetics

Methane acid, when applied to the surface of the epidermis, irritates the nerve endings of the skin and muscle tissue, activates specific reflex reactions, stimulates the production neuropeptides And enkephalins . This reduces pain sensitivity and increases vascular permeability. The substance stimulates liberation processes kinins And histamine , dilates blood vessels, stimulates immunological processes.

Indications for use

The drug is used to treat instruments and equipment before surgery. The substance is used topically in solutions for the treatment of rheumatic pain, periarthritis , poly- And monoarthritis .

Contraindications

The product should not be used if it is present, at the site of application, or if there are wounds or abrasions on the skin.