Chemical properties of obtaining and using carboxylic acids. Obtaining carboxylic acids

28.09.2019 alternative energy

Chemical compounds, which also consist of the carboxyl group COOH, have received the name carboxylic acids from scientists. There are many names for these compounds. They are classified according to various parameters, such as the number of functional groups, the presence of an aromatic ring, and so on.

The structure of carboxylic acids

As already mentioned, in order for an acid to be carboxylic, it must have a carboxyl group, which, in turn, has two functional parts: hydroxyl and carbonyl. Their interaction is provided by its functional combination of one carbon atom with two oxygen atoms. Chemical properties carboxylic acids depends on the structure of this group.

Due to the carboxyl group, these organic compounds can be called acids. Their properties are due to the increased ability of the hydrogen ion H + to attract oxygen, additionally polarizing O-H bond. Also, due to this property, organic acids are able to dissociate in aqueous solutions. The solubility decreases in inverse proportion to the increase in the molecular weight of the acid.

Varieties of carboxylic acids

Chemists distinguish several groups of organic acids.

Monobasic carboxylic acids consist of a carbon skeleton and only one functional carboxyl group. Every student knows the chemical properties of carboxylic acids. Grade 10 curriculum in chemistry includes directly studying the properties of monobasic acids. Dibasic and polybasic acids have two or more carboxyl groups in their structure, respectively.

Also, according to the presence or absence of double and triple bonds in the molecule, there are unsaturated and saturated carboxylic acids. Chemical properties and their differences will be discussed below.

If a organic acid has a substituted atom in the radical, then the name of the substituent group is included in its name. So, if the hydrogen atom is replaced by a halogen, then the name of the halogen will be present in the name of the acid. The name will undergo the same changes if there is a substitution for aldehyde, hydroxyl or amino groups.

Isomerism of organic carboxylic acids

Soap production is based on the reaction of synthesis of esters of the above acids with potassium or sodium salt.

Methods for obtaining carboxylic acids

There are many ways and methods for obtaining acids with a COOH group, but the following are most often used:

Isolation from natural substances (fats and other).
Oxidation of monoalcohols or compounds with a COH group (aldehydes): ROH (RCOH) [O] R-COOH.
Hydrolysis of trihaloalkanes in alkali with intermediate production of monoalcohol: RCl3 +NaOH=(ROH+3NaCl)=RCOOH+H2O.
Saponification or hydrolysis of acid and alcohol esters (esters): R−COOR"+NaOH=(R−COONa+R"OH)=R−COOH+NaCl.
Oxidation of alkanes with permanganate (hard oxidation): R=CH2 [O], (KMnO4) RCOOH.

The value of carboxylic acids for humans and industry

The chemical properties of carboxylic acids have great importance for human life. They are extremely necessary for the body, as in in large numbers contained in each cell. The metabolism of fats, proteins and carbohydrates always goes through a stage at which this or that carboxylic acid is obtained.

In addition, carboxylic acids are used to create medicines. No pharmaceutical industry can exist without the practical application of the properties of organic acids.

Compounds with a carboxyl group also play an important role in the cosmetic industry. Synthesis of fat for the subsequent production of soap, detergents and household chemicals based on an esterification reaction with a carboxylic acid.

The chemical properties of carboxylic acids are reflected in human life. They are of great importance for human body, since they are found in large quantities in each cell. The metabolism of fats, proteins and carbohydrates always goes through a stage at which this or that carboxylic acid is obtained.

carboxylic acids compounds that contain a carboxyl group are called:

Carboxylic acids are distinguished:

monobasic carboxylic acids;
dibasic (dicarboxylic) acids (2 groups UNSD).

Depending on the structure, carboxylic acids are distinguished:

aliphatic;
alicyclic;
aromatic.

Examples of carboxylic acids.

Obtaining carboxylic acids.

1. Oxidation of primary alcohols with potassium permanganate and potassium dichromate:

2. Hydrolysis of halogenated hydrocarbons containing 3 halogen atoms at one carbon atom:

3. Obtaining carboxylic acids from cyanides:

When heated, the nitrile hydrolyzes to form ammonium acetate:

When acidified, acid precipitates:

4. Use of Grignard reagents:

5. Hydrolysis of esters:

6. Hydrolysis of acid anhydrides:

7. Specific methods for obtaining carboxylic acids:

Formic acid is obtained by heating carbon monoxide (II) with powdered sodium hydroxide under pressure:

Acetic acid is obtained by catalytic oxidation of butane with atmospheric oxygen:

Benzoic acid is obtained by oxidation of monosubstituted homologues with a solution of potassium permanganate:

Cannicaro's reaction. Benzaldehyde is treated with 40-60% sodium hydroxide solution at room temperature.

Chemical properties of carboxylic acids.

In an aqueous solution, carboxylic acids dissociate:

The equilibrium is shifted strongly to the left, because carboxylic acids are weak.

Substituents affect acidity through an inductive effect. Such substituents pull the electron density towards themselves and a negative inductive effect (-I) arises on them. Pulling the electron density leads to an increase in the acidity of the acid. Electron donor substituents create a positive inductive charge.

1. Formation of salts. Reacting with basic oxides, salts weak acids and active metals:

Carboxylic acids are weak, because mineral acids displace them from the corresponding salts:

2. Formation of functional derivatives of carboxylic acids:

3. Esters when an acid is heated with alcohol in the presence of sulfuric acid - an esterification reaction:

4. Formation of amides, nitriles:

3. The properties of acids are determined by the presence of a hydrocarbon radical. If the reaction proceeds in the presence of red phosphorus, it forms the following product:

4. Addition reaction.

8. Decarboxylation. The reaction is carried out by fusing an alkali with an alkali metal salt of a carboxylic acid:

9. Dibasic acid easily splits off CO 2 when heated:

Additional materials on the topic: Carboxylic acids.

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Department of the Altai Territory for Education and Youth Affairs

KGOU SPO "Kamensky Pedagogical College"

carboxylic acids

(Abstract in chemistry)

Completed:

student of group 212 Chebakov D.S.

Checked:

chemistry teacher Merzlova S.A.

Stone-on-Obi

1. Determination of Carboxylic acids

2. Isomerism and nomenclature

3. Being in nature

4. Receipt

5.Physical Properties

6.Chemical properties

7.Application

Bibliography

Definition of carboxylic acids

carboxylic acids- organic compounds containing one or more carboxyl groups -COOH. The name comes from lat. carbo - coal and Greek. oxys - sour. According to the number of these groups, mono-, di, tri- and tetracarboxylic acids are distinguished (a larger number of -COOH groups in one molecule is rare). Carboxylic acids can be aliphatic - with a normal and branched chain, cyclic and aromatic, saturated and unsaturated, contain halogen atoms and various functional groups: OH (hydroxy acids), NH2 (amino acids), CO (keto acids), etc. Many carboxylic acids in the free state, as well as in the form of various derivatives (salts, esters) are widely distributed in nature and play an important role in the life of plants and animals.

Isomerism and nomenclature

The isomerism of saturated monobasic carboxylic acids is similar to that of aldehydes. Most often, the historical names of acids are used (formic, acetic, etc.). According to the international nomenclature, they are formed from the names of the corresponding hydrocarbons with the addition of the ending - new and the words "Acid", for example: methanoic acid, ethanoic acid.

Carboxylic acids are characterized by isomerism:

1.Carbon skeleton

CH3 - CH2 - CH2 - CH2 -COOH

CH2 - CH2 -COOH

carboxylic acid organic chemical

2. Radical

CH3 - CH2 - CH2 - CH2 -COOH 3 methylethane

CH3 - CH2 - CH2 - CH2 -COOH 4 methylpentane

3. Multiple bonds

CH2 \u003d CH - CH2 -COOH butenoic acid 3

CH2 - CH \u003d CH2 -COOH butenoic acid 2

Being in nature

Natural sources in the form of esters contain many unsaturated acids. Higher unsaturated acids, as a rule, contain an even number of carbon atoms and are named after natural sources. Naming the newly isolated acids, chemists often give free rein to their imagination. Thus, the name of the nearest homologue of acrylic acid, crotonic CH3-CH=CH-COOH, does not come from the mole at all, but from the plant Croton tiglium, from whose oil it was isolated. The synthetic isomer of crotonic acid is very important - methacrylic acid CH2=C(CH3)-COOH, from the ester of which (methyl methacrylate), as well as from methyl acrylate, they make transparent plastic - plexiglass. When two isomeric acids were discovered, having the structure CH3-CH=C(CH3)-COOH, they were called angelic and tiglinic. Angelic acid was isolated from angelic oil obtained from the angelic (angelica) root of the Angelica officinalis plant. And tiglinic - from the same Croton tiglium oil as crotonic acid, only named after the second part of this botanical term. Another way to come up with a new name is to rearrange the letters in an already known name.

Arachinic acid found in oil peanut- peanuts. In terms of production scale, it occupies one of the first places among all edible oils, but there is little arachidic acid itself in it - only a few percent. Behenic acid is found in behen oil, which is squeezed out of the large, nut-like seeds of a plant of the moringa family common in Indonesia. Almost pure lignoceric acid (in its name it is easy to see the Latin lignum - wood, wood and cera - wax) is extracted from the resin of a beech tree. Previously, this acid was also called carnaubic acid, because it is quite abundant in carnauba wax, which is covered with leaves of the Brazilian wax palm.

Fatty acids in the composition of oils and fats are extracted by man in huge quantities, measured annually by millions of tons. So chemists have never been short of natural fatty acids for their research.

Formic acid became known in the 17th century, when it was discovered in the caustic secretions of red ants. Most of the other acids, which have their "own" historical names, were obtained mainly in the 19th century. and named after natural source, in which they are contained in significant quantities or were first discovered. For example, butyric acid is found in oils, including ordinary butter- only not in a free state, but in the form of an ester with glycerol. Free butyric acid, like all carboxylic acids, a large number carbon atoms, has a pungent odor, when the oil deteriorates (rancid), butyric and other acids are released in a free state and give it bad smell and taste.

In the names of the three acids considered, Russian roots are used. For derivatives of these acids (salts, esters, etc.), it is customary to use Latin roots: formate - for formic acid (Latin formica - ant), acetate - for acetic acid (Latin acetum - vinegar), butyrate - for butyric acid (Greek. butyron - oil); these names, including those for the acids themselves, are also adopted in Western European languages.

Other carboxylic acids occur naturally as esters with glycerol and other polyhydric alcohols - in the form of fats, oils, waxes, and rarely - in the free state.

Valeric acid found in valerian root. The names of the next three even acids (caproic, caprylic and capric) have a common root (Capra in Latin - goat), these acids are indeed found in the fat of goat's milk (as, indeed, cow's), and in the free state "smell of a goat ". The content of these acids in milk fats is not very high - from 7 to 14% of the total of all fatty acids.

Pelargonic acid is found in the volatile oil of rosea pelargonium and other plants of the geranium family. Lauric acid (in old books it was called laurel) is found in large quantities in laurel oil (up to 45%). Myristic acid predominates in the oil of plants of the myristic family, for example, in the fragrant seeds of the nutmeg tree - nutmeg.

palmitic acid easily isolated from palm oil pressed from coconut kernels (copra). This oil consists almost entirely of palmitic acid glyceride. The name stearic acid comes from the Greek. stear - fat, fat. Together with palmitic, it is one of the most important fatty acids and makes up main part most vegetable and animal fats. From a mixture of these acids (stearin), candles were previously made.

Receipt

In the laboratory, carboxylic acids, as well as inorganic ones, can be obtained from their salts by acting on them with sulfuric acid when heated:

In industry, carboxylic acids are obtained in various ways.

A common method for obtaining carboxylic acids is the oxidation of hydrocarbons with atmospheric oxygen. The reaction is carried out both in the gas phase at elevated pressure and temperature without catalysts, and in solutions. In this case, the cracking of carbon chains occurs, so that the acids obtained in this way always contain fewer carbon atoms than the original hydrocarbons. For example, acetic acid is obtained by oxidizing N-butane in an acetic acid solution:

Mn, Co, 6-8 MPa

2CH3 - CH2 - CH2 - CH3 + 5O2 4CH3COOH + 2H2O

Physical Properties

Lower carboxylic acids are liquids with a pungent odor, highly soluble in water. As the relative molecular weight increases, the solubility of acids in water decreases and the boiling point rises. Higher acids, starting with pelargonic (n-nonanoic) CH3-(CH2)7-COOH, are solids, odorless, insoluble in water. Lower carboxylic acids in anhydrous form and in concentrated solutions irritate the skin and cause burns, especially formic acid and acetic acid.

Chemical properties

The general properties of carboxylic acids are similar to those of inorganic acids.

Carboxylic acids also have some specific properties due to the presence of radicals in their molecules. For example, acetic acid reacts with chlorine:

monochloroacetic acid

Formic acid is somewhat different in chemical properties from other carboxylic acids.

1. Of the monobasic carboxylic acids, formic acid is the strongest acid.

2. Due to the structural features of the molecules, formic acid, like aldehydes, is easily oxidized (the "silver mirror" reaction):

carbonic acid.

3. When heated with concentrated sulfuric acid, formic acid splits off water and carbon monoxide (II) is formed:

This reaction is sometimes used to produce carbon(II) monoxide in the laboratory.

As already noted, the strongest of the monobasic carboxylic acids is formic acid.

Acetic acid much weaker. Therefore, the methyl CH3 - radical (and other radicals) affects the carboxyl group. As a result, the bond between the hydrogen and oxygen atoms in the carboxyl group becomes less polar and the elimination of the hydrogen ion becomes more difficult. In carboxylic acid radicals, hydrogen atoms can be replaced by halogens. In this case, substitution occurs more easily in the hydrocarbon unit, which is closer to the carboxyl group. Therefore, the carboxyl group acts on the hydrocarbon radical, that is, their influence is mutual.

Application

Formic acid is used in industry as a strong reducing agent. Its 1.25% solution in alcohol (formic alcohol) is used in medicine. Highest value acetic acid has it; it is necessary for the synthesis of dyes (for example, indigo), medicines (for example, aspirin), esters, acetic anhydride, monochloroacetic acid, etc. Large quantities of it are used for the production of acetate fiber, non-combustible film, organic glass that transmits UV rays.

Widely used are its salts - acetates. Lead (II) acetate is used for the manufacture of white lead and lead lotion in medicine, iron (III) and aluminum acetates - as mordants when crumbling fabrics, copper (II) acetate - for pest control. 3-9% aqueous solution of acetic acid - vinegar - flavoring and preservative. Some compounds that use acetic acid, such as the sodium salt of 2,4-dichlorophenoxyacetic acid, are herbicides for weed control. Sodium and potassium salts of higher carboxylic acids are the main constituents of soap.

Esters of formic acid are used as solvents and fragrances

Bibliography

G.E. Rudzitis, F.G. Feldman Chemistry: Organic Chemistry: Textbook for 10 cells. educational institutions. - 5th ed. - M.: Enlightenment, 1998. - 160 p.

O.S.Gabrielyan Chemistry. Grade 10: Textbook for educational institutions / O.S. Gabrielyan. - 11th ed., Rev. M. : Bustard, 2006.- 267, p.

L.S. Guzey Chemistry. Grade 11: Textbook for educational institutions / R.P. Surovtseva, G.G. Lysova - 7th ed., stereotype. M. : Bustard, 2006. - 223, p.

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Class of carboxylic acids: general characteristics

From the point of view of the science of chemistry, this class of compounds includes oxygen-containing molecules that have a special grouping of atoms - a carboxyl functional group. It looks like -COOH. In this way, general formula, which all saturated monobasic carboxylic acids have, looks like this: R-COOH, where R is a radical particle, which can include any number of carbon atoms.

Accordingly, the definition of this class of compounds can be given as follows. Carboxylic acids are organic oxygen-containing molecules, which include one or more functional groups -COOH - carboxyl groups.

The fact that these substances belong specifically to acids is explained by the mobility of the hydrogen atom in the carboxyl. The electron density is distributed unevenly, since oxygen is the most electronegative in the group. From this O-N connection strongly polarized, and the hydrogen atom becomes extremely vulnerable. It is easily split off, entering into chemical interactions. Therefore, the acids in the corresponding indicators give a similar reaction:

Due to the hydrogen atom, carboxylic acids exhibit oxidizing properties. However, the presence of other atoms allows them to recover, to participate in many other interactions.

Classification

There are several main features by which carboxylic acids are divided into groups. The first of these is the nature of the radical. According to this factor, there are:

Alicyclic acids. Example: quinine.
Aromatic. Example: benzoic.
Aliphatic. Example: acetic, acrylic, oxalic and others.
Heterocyclic. Example: nicotine.

If we talk about bonds in a molecule, then we can also distinguish two groups of acids:

The number of functional groups can also serve as a sign of classification. Thus, the following categories are distinguished.

Monobasic - only one -COOH group. Example: formic, stearic, butane, valeric and others.
Dibasic- respectively, two groups -COOH. Example: oxalic, malonic and others.
Multibase- lemon, milk and others.

Discovery history

Winemaking has flourished since antiquity. And, as you know, one of its products is acetic acid. Therefore, the history of the popularity of this class of compounds dates back to the time of Robert Boyle and Johann Glauber. However, in this case, the chemical nature of these molecules should be clarified for a long time failed.

After all, for a long time the views of vitalists dominated, who denied the possibility of the formation of organic matter without living beings. But already in 1670, D. Ray managed to get the very first representative - methane or formic acid. He did this by heating live ants in a flask.

Later, the work of scientists Berzelius and Kolbe showed the possibility of synthesizing these compounds from inorganic substances(distillation of charcoal). The result was acetic acid. Thus, carboxylic acids (physical properties, structure) were studied and a start was made for the discovery of all other representatives of a number of aliphatic compounds.

Physical Properties

Today, all their representatives have been studied in detail. For each of them, you can find a characteristic in all respects, including application in industry and being in nature. We will consider what carboxylic acids are, their and other parameters.

So, there are several main characteristic parameters.

If the number of carbon atoms in the chain does not exceed five, then these are sharp-smelling, mobile and volatile liquids. Above five - heavy oily substances, even more - solid, paraffin-like.
The density of the first two representatives exceeds unity. Everything else is lighter than water.
Boiling point: the larger the chain, the higher the rate. The more branched the structure, the lower.
Melting point: depends on the evenness of the number of carbon atoms in the chain. Even ones are higher, odd ones are lower.
They dissolve very well in water.
Capable of forming strong hydrogen bonds.

Such features are explained by the symmetry of the structure, and hence the structure of the crystal lattice, its strength. The simpler and more structured molecules, the higher the performance that carboxylic acids give. The physical properties of these compounds make it possible to determine the areas and ways of using them in industry.

Chemical properties

As we have already indicated above, these acids can exhibit different properties. Reactions involving them are important for the industrial synthesis of many compounds. Let us denote the most important chemical properties that a monobasic carboxylic acid can exhibit.

Dissociation: R-COOH = RCOO - + H +.
Shows, that is, interacts with basic oxides, as well as their hydroxides. FROM simple metals interacts according to the standard scheme (that is, only with those that stand before hydrogen in a series of voltages).
With more strong acids(inorganic) behaves like a base.
Able to recover to primary alcohol.
A special reaction is esterification. This is an interaction with alcohols to form a complex product - an ether.
The reaction of decarboxylation, that is, the removal of a carbon dioxide molecule from a compound.
Able to interact with halides of elements such as phosphorus and sulfur.

It is obvious how versatile carboxylic acids are. Physical properties, as well as chemical ones, are quite diverse. In addition, it should be said that, in general, in terms of strength as acids, all organic molecules are rather weak compared to their inorganic counterparts. Their dissociation constants do not exceed 4.8.

How to get

There are several main ways in which saturated carboxylic acids can be obtained.

1. In the laboratory, this is done by oxidation:

alcohols;
aldehydes;
alkynes;
alkylbenzenes;
destruction of alkenes.

2. Hydrolysis:

esters;
nitriles;
amides;
trihaloalkanes.

4. In industry, synthesis is carried out by the oxidation of hydrocarbons with a large number of carbon atoms in the chain. The process is carried out in several stages with the release of many by-products.

5. Some individual acids (formic, acetic, butyric, valeric and others) are obtained in specific ways using natural ingredients.

Basic compounds of saturated carboxylic acids: salts

Salts of carboxylic acids are important compounds used in industry. They are obtained as a result of the interaction of the latter with:

metals;
basic oxides;
alkalis;
amphoteric hydroxides.

Especially importance among them are those that are formed between the alkali metals sodium and potassium and the highest saturated acids - palmitic, stearic. After all, the products of such interaction are soaps, liquid and solid.

Soaps

So, if we are talking about a similar reaction: 2C 17 H 35 -COOH + 2Na \u003d 2C 17 H 35 COONa + H 2,

then the resulting product - sodium stearate - is by its nature the usual laundry soap used for washing clothes.

If you replace the acid with palmitic, and the metal with potassium, you get potassium palmitate - a liquid soap for washing hands. Therefore, it can be stated with confidence that salts of carboxylic acids are in fact important compounds of an organic nature. Their industrial production and use is simply colossal in its scale. If we imagine how much soap each person on Earth spends, then it is easy to imagine these scales.

Esters of carboxylic acids

A special group of compounds that has its own place in the classification of organic substances. This class They are formed by the reaction of carboxylic acids with alcohols. The name of such interactions is esterification reactions. General form can be represented by the equation:

R, -COOH + R "-OH \u003d R, -COOR" + H 2 O.

The product with two radicals is an ester. Obviously, as a result of the reaction, the carboxylic acid, alcohol, ester and water have undergone significant changes. So, hydrogen leaves the acid molecule in the form of a cation and meets with a hydroxo group that has split off from alcohol. The result is a water molecule. The group left from the acid attaches the radical from the alcohol to itself, forming an ester molecule.

Why are these reactions so important and what is the industrial significance of their products? The thing is that esters are used as:

nutritional supplements;
aromatic additives;
an integral component of perfume;
solvents;
components of varnishes, paints, plastics;
medicines and more.

It is clear that the areas of their use are wide enough to justify the volume of production in the industry.

Ethanoic acid (acetic)

This is the limiting monobasic carboxylic acid of the aliphatic series, which is one of the most common in terms of production throughout the world. Its formula is CH 3 COOH. Such prevalence is due to its properties. After all, the areas of its use are extremely wide.

She is food additive under the code E-260.
It is used in the food industry for conservation.
It is used in medicine for the synthesis of drugs.
Component in the production of fragrant compounds.
Solvent.
Participant in the process of printing, dyeing fabrics.
A necessary component in the reactions of chemical synthesis of many substances.

In everyday life, its 80% solution is usually called vinegar essence, and if you dilute it to 15%, you get just vinegar. Pure 100% acid is called glacial acetic acid.

Formic acid

The very first and simplest representative of this class. Formula - NCOON. It is also a food additive under the code E-236. Its natural sources:

ants and bees;
nettle;
needles;
fruit.

Main areas of use:

Also in surgery, solutions of this acid are used as antiseptics.

Obtaining carboxylic acids

I. In industry

1. Isolate from natural products

(fats, waxes, essential and vegetable oils)

2. Alkanes oxidation:

2CH 4 + + 3O 2 t,kat→ 2HCOOH + 2H2O

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 \u003d CH 2 + O 2 t,kat→CH3COOH

ethylene

FROM H 3 -CH \u003d CH 2 + 4 [O] t,kat→ CH 3 COOH + HCOOH (acetic acid + formic acid )

4. Oxidation of benzene homologues (obtaining 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. Obtaining formic acid:

1 stage: CO+NaOH t , p→HCOONa (sodium formate - salt )

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

6. Obtaining acetic acid:

CH 3 OH + 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 the preparation of carboxylic acids

1. Oxidation of aldehydes:

R-COH + [O] → R-COOH

For example, the "Silver Mirror" reaction or oxidation with copper (II) hydroxide - qualitative reactions of aldehydes

2. Oxidation of alcohols:

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

3. Hydrolysis of halogen-substituted hydrocarbons containing three halogen atoms on one carbon atom.

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

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

CH3-CN - methyl cyanide (acetic acid nitrile)

FROM 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

APPLICATIONS OF CARBOXY 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 obtained; for the synthesis of dyes, medicines and esters). AT household as a flavoring and preservative agent.

Butyric acid- to obtain flavoring additives, plasticizers and flotation reagents.

Oxalic acid– in the metallurgical industry (descaling).

Stearic C 17 H 35 COOH and palmitic acid C 15 H 31 COOH - as surfactants, lubricants in metalworking.

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

Individual representatives

monobasic limiting carboxylic acids

Formic acid was first isolated in the 17th century from red wood ants. It is also found in the juice of stinging nettle. Anhydrous formic acid is a colorless liquid with a pungent odor and burning taste that causes burns on the skin. It is used in the textile industry as a mordant for dyeing fabrics, for tanning leather, as well as for various syntheses.
Acetic acid widely distributed in nature - found in animal secretions (urine, bile, feces), in plants (in green leaves). It is formed during fermentation, rotting, souring of wine, beer, found in sour milk and cheese. The melting point of anhydrous acetic acid is + 16.5 ° C, its crystals are transparent like ice, therefore it is called glacial acetic acid. First received in late XVIII century by the Russian scientist T. E. Lovits. Natural vinegar contains about 5% acetic acid. Acetic essence is prepared from it, which is used in the food industry for canning 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. Widespread in nature in flora: in balms, incense, essential oils. In animal organisms, it is found in the breakdown products of protein substances. it crystalline substance, melting point 122°C, sublimes easily. AT cold water dissolves poorly. 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 these is oleic CH 3 - (CH 2) 7 -CH \u003d CH - (CH 2) 7 -COOH or C 17 H 33 COOH. It is a colorless liquid that hardens in the cold.
Especially important are polyunsaturated acids with several double bonds: linoleic CH 3 - (CH 2) 4 - (CH \u003d CH - CH 2) 2 - (CH 2) 6 -COOH or C 17 H 31 COOH with two double bonds, linolenic CH 3 -CH 2 - (CH \u003d 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 \u003d CH - CH 2) 4 - (CH 2) 2 - COOH with four double bonds; they are often referred to as essential fatty acids. It is these acids that have the greatest biological activity: they are involved in the transfer and metabolism of cholesterol, the synthesis of prostaglandins and other vital substances, maintain the structure cell membranes 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, causes various diseases. The human body cannot synthesize linoleic and linolenic acids on its own 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 esters of glycerol are found in the so-called drying oils - linseed, hemp, poppy, etc. Linoleic acid C 17 H 31 COOH 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.

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

The simplest unsaturated acid, acrylic CH 2 \u003d CHCOOH, has a pungent odor (in Latin acris - sharp, caustic). Acrylates (esters of acrylic acid) are used to produce organic glass, and its nitrile (acrylonitrile) is used to make synthetic fibers.

Naming the newly isolated acids, chemists often give free rein to their imagination. So, the name of the nearest homologue of acrylic acid, crotonic

CH 3 -CH \u003d CH -COOH, does not come from a mole at all, but from a plant Croton tiglium from the oil from which it was isolated. The synthetic isomer of crotonic acid is very important - methacrylic acid CH 2 \u003d C (CH 3) - COOH, from the ether of which (methyl methacrylate), as well as from methyl acrylate, they make transparent plastic - plexiglass.

Unsaturated carbon acids are capable of addition reactions:

CH 2 \u003d CH-COOH + H 2 → CH 3 -CH 2 -COOH

CH 2 \u003d CH-COOH + Cl 2 → CH 2 Cl -CHCl -COOH

VIDEO:

CH 2 \u003d CH-COOH + HCl → CH 2 Cl -CH 2 -COOH

CH 2 \u003d 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.

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