Palmitic acid[1] Names Preferred IUPAC name Other names Identifiers ChEMBL ChemSpider ECHA InfoCard 100.000.284 UNII Properties C16H32O2 Molar mass 256.430 g/mol Appearance White crystals Density 0.852 g/cm3 (25 °C)[2] 0.8527 g/cm3 (62 °C)[3] Melting point 62.9 °C (145.2 °F; 336.0 K)[7] Boiling point 351-352 °C (664-666 °F; 624-625 K)[8]271.5 °C (520.7 °F; 544.6 K), 100 mmHg[2] 215 °C (419 °F; 488 K), 15 mmHg 4.6 mg/L (0 °C) 7.2 mg/L (20 °C) 8.3 mg/L (30 °C) 10 mg/L (45 °C) 12 mg/L (60 °C)[4] Solubility Soluble in amyl acetate, alcohol, CCl4,[4] C6H6 Very soluble in CHCl3[3] Solubility in ethanol 2 g/100 mL (0 °C) 2.8 g/100 mL (10 °C) 9.2 g/100 mL (20 °C) 31.9 g/100 mL (40 °C)[5] Solubility in methyl acetate 7.81 g/100 g[4] Solubility in ethyl acetate 10.7 g/100 g[4] Vapor pressure 0.051 mPa (25 °C)[3] 1.08 kPa (200 °C) 28.06 kPa (300 °C)[6] Acidity (pKa) 4.75 [3] −198.6·10−6 cm3/mol 1.43 (70 °C)[3] Viscosity 7.8 cP (70 °C)[3] Thermochemistry 463.36 J/(mol·K)[6] 452.37 J/(mol·K)[6] −892 kJ/mol[6] 10030.6 kJ/mol[3] Hazards GHS labelling: [2] Warning H319[2] P305+P351+P338[2] NFPA 704 (fire diamond) Flash point 206 °C (403 °F; 479 K)[2]
Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and microorganisms.[9][10] Its chemical formula is CH3(CH2)14COOH, and its C:D ratio (the total number of carbon atoms to the number of carbon-carbon double bonds) is 16:0. It is a major component of palm oil from the fruit of Elaeis guineensis (oil palms), making up to 44% of total fats. Meats, cheeses, butter, and other dairy products also contain palmitic acid, amounting to 50-60% of total fats.[11]
Palmitates are the salts and esters of palmitic acid. The palmitate anion is the observed form of palmitic acid at physiologic pH (7.4). Major sources of C16:0 are palm oil, palm kernel oil, coconut oil, and milk fat.[12]
Dietary palmitic acid intake is associated with an increased cardiovascular disease risk through raising low-density lipoprotein.[13]
Palmitic acid was discovered by saponification of palm oil, which process remains today the primary industrial route for producing the acid.[14] Triglycerides (fats) in palm oil are hydrolysed by high-temperature water and the resulting mixture is fractionally distilled.[15]
Palmitic acid is produced by a wide range of plants and organisms, typically at low levels. Among common foods it is present in milk, butter, cheese, and some meats, as well as cocoa butter, olive oil, soybean oil, and sunflower oil, (see table).[16] Karukas contain 44.90% palmitic acid.[17] The cetyl ester of palmitic acid, cetyl palmitate, occurs in spermaceti.
Palmitic acid content of common foods Food % of total calories Palm oil 45.1% Beef tallow 26.5% Butter fat 26.2% Cocoa butter 25.8% Lard 24.8% Cottonseed oil 24.7% Chicken 23.2% Corn oil 12.2% Peanut oil 11.6% Soybean oil 11% Coconut oil 8.4% Palm kernel oil 8% Rapeseed oil 3.6% Source:[18]
Palmitic acid is the first fatty acid produced during fatty acid synthesis and is the precursor to longer fatty acids. As a consequence, palmitic acid is a major body component of animals. In humans, one analysis found it to make up 21-30% (molar) of human depot fat,[19] and it is a major, but highly variable, lipid component of human breast milk.[20] Palmitic acid comprises nearly half of total human brain saturated fatty acids.[21]
Palmitate negatively feeds back on acetyl-CoA carboxylase (ACC), which is responsible for converting acetyl-CoA to malonyl-CoA, which in turn is used to add to the growing acyl chain, thus preventing further palmitate generation.[22] Some proteins are modified by the addition of a palmitoyl group in a process known as palmitoylation. Palmitoylation is important for localisation of many membrane proteins.
Palmitic acid is used to produce soaps, cosmetics, and industrial mold release agents. These applications use sodium palmitate, which is commonly obtained by saponification of palm oil. To this end, palm oil, rendered from palm trees (species Elaeis guineensis), is treated with sodium hydroxide (in the form of caustic soda or lye), which causes hydrolysis of the ester groups, yielding glycerol and sodium palmitate.
Because it is inexpensive and adds texture and “mouthfeel” to processed foods (convenience food), palmitic acid and its sodium salt find wide use in foodstuffs. Sodium palmitate is permitted as a natural additive in organic products.[23]
Aluminium salts of palmitic acid and naphthenic acid were the gelling agents used with volatile petrochemicals during World War II to produce napalm. The word “napalm” is derived from the words naphthenic acid and palmitic acid.[24]
It is well accepted in the medical community that palmitic acid from dietary sources raises low-density lipoprotein (LDL) and total cholesterol.[18][25][26][27] The World Health Organization have stated there is convincing evidence that palmitic acid increases cardiovascular disease risk.[28] Palmitic acid intake is associated with an increased cancer risk, including prostate cancer.[29][30]
A 2021 review indicated that replacing dietary palmitic acid and other saturated fatty acids with unsaturated fatty acids, such as oleic acid, could reduce several biomarkers of cardiovascular and metabolic diseases.[31]
- Retinyl palmitate
- Ascorbyl palmitate
- SN2 Palmitate
- Juniperic acid (16-hydroxypalmitic acid)
- Media related to Palmitic acid at Wikimedia Commons
- “Palmitic Acid” . Encyclopædia Britannica (11th ed.). 1911.