Adipic acid. Properties and applications

Adipic acid (there is another name for this substance - acid 1,4-butanedicarboxylic acid, the systematic name - hexanedioic acid) is the limiting dibasic carboxylic acid. Has the following chemical formula: HOOC (CH2) 4COOH and the gross formula C6O4H10. It has the same chemical properties as carboxylic acids. Forms salts, many of which are soluble in water (H2O). It is esterified to di- and mono-esters. With glycols, hexanedioic acid forms polyesters.

Properties of adipic acid

1. The molar mass is 146.1 grams per mole.

2. The density is 1.36 grams / mole.

3. It is boundedly soluble in ethanol, diethyl alcohol and acetone.

4. The solubility in water (H2O) is: at 15 degrees, 1.44 g in 100 g of water; At 40 degrees, 5.12 g; At 70 degrees - 34.1 g.

Thermal properties of hexadioic acid

1. The melting point is 153 ° C.

2. The decomposition temperature is 210 - 240 ° C.

3. The boiling point (at 100 mmHg) is 265 ° C.

4. The decarboxylation temperature is 300-320 ° C.

5. The enthalpy of combustion is -2800 kJ / mol.

6. The melting enthalpy is 16.7 kJ / mol.

7. The enthalpy of evaporation is 18.7 kJ / mol.

How to get adipic acid?

In industry, this substance is produced mainly by two-stage oxidation of cyclohexane. First, a mixture of cyclohexanol and cyclohexanone is obtained, which is then separated by rectification. Subsequently, cyclohexanone is used to prepare caprolactam, and cyclohexanol is oxidized with 40-60% HNO3 (nitric acid). With this method, the yield of adipic acid is about ninety-five percent.

One of the promising ways of producing adipic acid is the hydrocarbonylation of butadiene.

What other methods are used to produce carboxylic acids, such as adipic acid? It can also be obtained by oxidizing cyclohexane with nitric acid (HNO3) at a temperature of +100-200 ° C, dinitrogen tetroxide (N2O4) at a temperature of +50 ° C or ozone (O3).

Adipic acid is also obtained by carbonylation of THF (tetrahydrofuran) into adipic anhydride, from which the substance we are considering is then obtained.

The use of adipic acid:

- this substance is a raw material (it is used about ninety percent of all produced acid) in the production of polyhexamethyleneadipamide, as well as its polyurethanes and esters;

- it is used as a food additive (registered under number Е 355) for giving the products an acid taste (including the production of soft drinks);

- adipic acid is the main component of the funds intended for descaling;

- used to remove the material that remained after filling the seams between the ceramic tiles;

- The use of carboxylic acids, such as adipic, is important for the synthesis of intermediate products.

What are the chemical reactions of adipic acid?

1. This substance reacts with various metals, their basic hydroxides and oxides to give the corresponding salts.

2. May displace the weaker acid from its salt.

3. In the presence of an acid catalyst, adipic acid reacts with alcohols. In this case, esters are formed .

4. When ammonium salts of adipic acid are heated, their amides are formed.

5. Under the influence of SOCl2, adipic acid is converted to the corresponding acid chloride.

Esters of adipic acid  

1. Methyl adipate is used for the electrochemical synthesis of dimethyl sebacate.

2. Diallyl dipinate is a curing agent for polyester resins.

3. Ethyl adipate is used as an additive to leaded gasoline in order to increase its octane number.

4. Diethyladipinate is used as a plasticizer in the production of food films, shoes, PVC, artificial leather, children's toys, linoleum, stretch ceilings.

5. Diisopropyl adipate is used as a component of cosmetic products for the skin.