Palmitic acid. Properties, production, application

Palmitic acid (also known as hexadecanoic acid) is a saturated monobasic carboxylic (fatty) acid. The most common in nature. This substance was first found in palm oil. Esters and salts of this acid are called palmitates. Numerous ethers of this acid are crystalline and resemble wax. Has the following chemical formula: CH3 (CH2) 14COOH. And its empirical formula is: C16H32O2.

The discovery of palmitic acid in nature

This substance is found in the composition of glycerides of most vegetable oils and animal fats. For example, soybean oil contains 6.5%, palm oil - 38-47%, lard - 30%. In addition, hexadecanoic acid is part of some waxes: sperm whale contains 90% cetyl ether hexadecanoic acid, and in beeswax about 30% of its myristyl ether. In animal organisms, palmitic acid is the final product of the synthesis of fatty acids from acetyl-CoA.

In the form of glyceride, hexadecanoic acid is found in palm oil, in vegetable fat of North American and Chinese fruits Croton sebiferum and Stillinga sebifera, in Rhus succedanea seeds (in wax), in myicone wax from Myrica cerifera berries, in lanolin. In the free state palmitic acid is found in the seeds of paprika, in spores of Lycopodium and in cadaver wax (is the main part).

Physical properties of palmitic acid:

1. Condition (under standard conditions) - colorless crystals.

2. The molar mass is equal to 256, 43 g / mol.

3. The density is 0.841 g / cm³.

Thermal properties of palmitic acid:

1. The melting point is 62.9 ° C.

2. The boiling point is 105 ° C (at 0.01 mm Hg) and 167 ° C (at 1 mm Hg).

3. The flash point is 192 ° C.

4. The molar heat capacity (under normal conditions) is 460 J / (mol · K).

What are the chemical properties of hexadecanoic acid?

1. The solubility in water is 0.0007 (at 20 ° C).

2. The solubility in ethanol is 2600 (at 7.2 ° C).

3. Palmitic acid is moderately soluble in benzene and acetone.

Optical properties of palmitic acid:

1. The refractive index is 1.4219.

Preparation of palmitic acid

This substance can be obtained in several ways:

1. Through fractional crystallization or re-ratification from a mixture of fatty acids that were obtained by saponification of fat or oxidation of paraffins.

2. By heating cetyl alcohol with lime sodium to 270 ° C (Stas and Dumas).

C16H33OH (cetyl alcohol) + O2 (oxygen) = C15H31COOH + H2O (water)

3. When melting elaidinic (oleic) acid with sodium hydroxide:

CH3 (CH2) 7CH (oleic acid) = CH (CH2) 7COOH + H2O (water) + O = C15H31COOH (palmitic acid, formula) + CH3COOH (acetic acid)

4. When acid is oxidized with nitric 2-octodecanone:

CH3 (CH2) 15-CO-CH3 + 3O (oxygen) = C15H31COOH (hexadecanoic acid) + CH3COOH (acetic acid)

5. This substance can also be synthesized by the method of cyanide compounds from iodine of pentadecyl alcohol:

C15H31J + KCN (cyanide compound) = KJ + C15H31-CN;

C15H31-CN (cyanide compound) + 2H2O (water) = C15H31COOH (the resulting material) + NH3

Where is palmitic acid used?

1. The substance we are considering is used in the production of napalm, stearin (a special mixture with stearic acid), opaque cosmetic and various detergents, plasticizers and lubricating oils. In technology, this acid is used to make candles.

2. Calcium palmitate is used as a component of formulations to protect against moisture and water (hydrophobization) of the skin, various tissues, wood, opaque cosmetics and decorative cosmetics.

3. Also used and palmitate sodium as a component (thickener) toilet and laundry soaps, emulsifier, as part of cosmetic preparations.

4. Methyl palmitate is needed to produce palmitic acid and some of its derivatives, hexadecanol. Also this substance is used as a flavor for food products.

5. Previously, the lead salt of hexadecanoic acid was used to produce pharmaceutical patches.