Palmitate
Palmitic acid
Chemical compound
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]
| Names | |
|---|---|
| Preferred IUPAC name
Hexadecanoic acid | |
| Other names
Palmitic acid C16:0 (Lipid numbers) | |
| Identifiers | |
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3D model (JSmol) |
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| ChEMBL | |
| ChemSpider |
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| ECHA InfoCard | 100.000.284  |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| 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)[4] |
| Boiling point | 351–352 °C (664–666 °F; 624–625 K)[5] 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)[6] | |
| Solubility | Soluble in amyl acetate, alcohol, CCl4,[6] 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)[7] |
| Solubility in methyl acetate | 7.81 g/100 g[6] |
| Solubility in ethyl acetate | 10.7 g/100 g[6] |
| Vapor pressure | 0.051 mPa (25 °C)[3] 1.08 kPa (200 °C) 28.06 kPa (300 °C)[8] |
| Acidity (pKa) | 4.75 [3] |
| −198.6·10−6 cm3/mol | |
Refractive index (nD) |
1.43 (70 °C)[3] |
| Viscosity | 7.8 cP (70 °C)[3] |
| Thermochemistry | |
Heat capacity (C) |
463.36 J/(mol·K)[8] |
Std molar entropy (S⦵298) |
452.37 J/(mol·K)[8] |
Std enthalpy of formation (ΔfH⦵298) |
−892 kJ/mol[8] |
Std enthalpy of combustion (ΔcH⦵298) |
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] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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]
Palmitic acid was discovered by Edmond Frémy (in 1840) in the saponification of palm oil, which process remains today the primary industrial route for producing the acid.[13] Triglycerides (fats) in palm oil are hydrolysed by high-temperature water and the resulting mixture is fractionally distilled.[14]
Dietary sources
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).[15] Karukas contain 44.90% palmitic acid.[16] The cetyl ester of palmitic acid, cetyl palmitate, occurs in spermaceti.
| 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:[17] | |
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,[18] and it is a major, but highly variable, lipid component of human breast milk.[19] 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.[20]
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.
Surfactant
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.
Foods
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.[21]
Military
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.[22]
It is well accepted in the medical community that palmitic acid from dietary sources raises low-density lipoprotein (LDL) and total cholesterol.[17][23][24][25] The World Health Organization have stated there is convincing evidence that palmitic acid increases cardiovascular disease risk.[26]
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.[27]
- Retinyl palmitate
- Ascorbyl palmitate
- SN2 Palmitate
- Juniperic acid (16-hydroxypalmitic acid)
- Merck Index, 12th Edition, 7128.
- Sigma-Aldrich Co., Palmitic acid. Retrieved on 2014-06-02.
- Beare-Rogers, J.; Dieffenbacher, A.; Holm, J.V. (2001). "Lexicon of lipid nutrition (IUPAC Technical Report)". Pure and Applied Chemistry. 73 (4): 685–744. doi:10.1351/pac200173040685. S2CID 84492006.
- Palmitic acid at Inchem.org
- Seidell, Atherton; Linke, William F. (1952). Solubilities of Inorganic and Organic Compounds. Van Nostrand. Retrieved 2014-06-02.
- n-Hexadecanoic acid in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-05-11)
- Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The Lipid Handbook, 3rd ed. Boca Raton: CRC Press, 2007. ISBN 0849396883 | ISBN 978-0849396885
- The most common fatty acid is the monounsaturated oleic acid. See: https://pubchem.ncbi.nlm.nih.gov/compound/965#section=Top
- Loften, J.R.; Linn, J.G.; Drackley, J.K.; Jenkins, T.C.; Soderholm, C.G.; Kertz, A.F. (August 2014). "Invited review: Palmitic and stearic acid metabolism in lactating dairy cows". Journal of Dairy Science. 97 (8): 4661–4674. doi:10.3168/jds.2014-7919. ISSN 0022-0302. PMID 24913651.
- Frémy, E. (1842). "Memoire sur les produits de la saponification de l'huile de palme". Journal de Pharmacie et de Chimie. XII: 757.
- Anneken, David J.; Both, Sabine; Christoph, Ralf; Fieg, Georg; Steinberner, Udo; Westfechtel, Alfred (2006). "Fatty Acids". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a10_245.pub2. ISBN 978-3527306732.
- "Chemical Characteristics". Olive Oil Source. Retrieved November 11, 2021.[dead link]
- Nelson, Gary J. (1991). Health Effects of Dietary Fatty Acids. American Oil Chemists' Society. pp. 84-86. ISBN 978-0935315318
- Kingsbury, K. J.; Paul, S.; Crossley, A.; Morgan, D. M. (1961). "The fatty acid composition of human depot fat". Biochemical Journal. 78 (3): 541–550. doi:10.1042/bj0780541. PMC 1205373. PMID 13756126.
- Jensen, RG; Hagerty, MM; McMahon, KE (June 1978). "Lipids of human milk and infant formulas: a review". Am. J. Clin. Nutr. 31 (6): 990–1016. doi:10.1093/ajcn/31.6.990. PMID 352132.
- "Fatty acid biosynthesis - Reference pathway". KEGG. Pathway Map 00061
- US Soil Association standard 50.5.3
- Mysels, Karol J. (1949). "Napalm. Mixture of Aluminum Disoaps". Industrial & Engineering Chemistry. 41 (7): 1435–1438. doi:10.1021/ie50475a033.
- Mensink RP, Zock PL, Kester AD, Katan MB (2003). "Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials". Am J Clin Nutr. 77 (5): 1146–1155. doi:10.1093/ajcn/77.5.1146. PMID 12716665.
- Mensink, Ronald P. (2016). "Effects of saturated fatty acids on serum lipids and lipoproteins: a systematic review and regression analysis". World Health Organization. Retrieved 14 March 2023.
- Rao, Gundu HR. (2020). Clinical Handbook of Coronary Artery Disease. Jaypee Brothers Medical Publishers. pp. 186-187. ISBN 978-9389188301
- "Diet, Nutrition and the Prevention of Chronic Diseases". World Health Organization. p. 82. Retrieved 16 March 2023.
- Sellem, Laury; Flourakis, Matthieu; Jackson, Kim G; Joris, Peter J; Lumley, James; Lohner, Szimonetta; Mensink, Ronald P; Soedamah-Muthu, Sabita S; Lovegrove, Julie A (2021-11-25). "Impact of Replacement of Individual Dietary SFAs on Circulating Lipids and Other Biomarkers of Cardiometabolic Health: A Systematic Review and Meta-Analysis of Randomized Controlled Trials in Humans". Advances in Nutrition. 13 (4): 1200–1225. doi:10.1093/advances/nmab143. ISSN 2161-8313. PMC 9340975. PMID 34849532.
Media related to Palmitic acid at Wikimedia Commons- "Palmitic Acid" . Encyclopædia Britannica (11th ed.). 1911.
