Palmitic acid (another name is hexadecanoic acid) is a saturated monobasic carboxylic (fatty) acid. Most common in nature. This substance was first found in palm oil. The esters and salts of this acid are called palmitates. Numerous esters of this acid are crystalline and resemble wax. It has the following chemical formula: CH3 (CH2) 14COOH. And its empirical formula is: C16H32O2.
Finding palmitic acid in nature
This substance is in the glycerides of most oils of plant origin and animal fats. For example, its soybean oil contains 6.5%, palm oil - 38-47%, lard - 30%. In addition, hexadecanoic acid is part of some waxes: sperm whale spermaceti contains 90% of cetyl ether of hexadecanoic acid, and beeswax contains about 30% of its myristyl ether. In animals, 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 myricon wax from Myrica cerifera berries, in lanolin. In its free state, palmitic acid is found in paprika seeds, in Lycopodium spores and in cadaveric wax (is the main part).
Physical properties of palmitic acid:
1. Condition (under standard conditions) - colorless crystals.
2. The molar mass is 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 mmHg) and 167 ° C (at 1 mmHg).
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. Solubility in water is 0.0007 (at 20 ° C).
2. The solubility in ethanol is 2600 (at 7.2 ° C).
3. Palmitic acid is sparingly soluble in benzene and acetone.
Optical properties of palmitic acid:
1. The refractive index is 1.4219.
Getting palmitic acid
This substance can be obtained in several ways:
1. By fractional crystallization or retification from a mixture of fatty acids, which were obtained by saponification of fats or oxidation of paraffins.
2. By heating cetyl alcohol with soda lime to 270 ° C (Stas and Dumas).
C16H33OH (cetyl alcohol) + O2 (oxygen) = C15H31COOH + H2O (water)
3. When melting elaidic (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 oxidized with nitric acid 2-octodecanone:
CH3 (CH2) 15-CO-CH3 + 3O (oxygen) = C15H31COOH (hexadecanoic acid) + CH3COOH (acetic acid)
5. Also, this substance can be synthesized by the method of cyanide compounds from pentadecyl alcohol iodur:
C15H31J + KCN (cyanide compound) = KJ + C15H31-CN;
C15H31-CN (cyanide compound) + 2H2O (water) = C15H31COOH (resulting material) + NH3
Where is palmitic acid used?
1. The substance under consideration 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 compositions for protection against moisture and water (hydrophobization) of the skin, various tissues, wood, opaque cosmetics and decorative cosmetics.
3. Also use sodium palmitate as a component (thickener) of toilet and laundry soaps, emulsifier, as part of cosmetic preparations.
4. Methyl palmitate is needed to obtain palmitic acid and some of its derivatives, hexadecanol. This substance is also used as a flavoring agent for food products.
5. Previously, the lead salt of hexadecanoic acid was used for the production of pharmaceutical plasters.