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Palmitic acid, or hexadecanoic acid in IUPAC nomenclature, is the most common saturated fatty acid found in animals, plants and microorganisms.[9] Its chemical formula is CH3(CH2)14COOH, and its C:D is 16:0. As its name indicates, it is a major component of the oil from the fruit of oil palms (palm oil). Palmitic acid can also be found in meats, cheeses, butter, and dairy products. Palmitate is the salts and esters of palmitic acid. The palmitate anion is the observed form of palmitic acid at physiologic pH (7.4).

Palmitic acid[1]
Palmitic acid.svg
Palmitic-acid-3D-balls.png
Names
Preferred IUPAC name
Hexadecanoic acid
Other names
Palmitic acid
C16:0 (Lipid numbers)
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.000.284
Properties
C16H32O2
Molar mass 256.43 g·mol−1
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) [8]
Boiling point 351–352 °C (664–666 °F; 624–625 K) [4]
271.5 °C (520.7 °F; 544.6 K)
at 100 mmHg[2]
215 °C (419 °F; 488 K)
at 15 mmHg
0.46 mg/L (0 °C)
0.719 mg/L (20 °C)
0.826 mg/L (30 °C)
0.99 mg/L (45 °C)
1.18 mg/L (60 °C)[5]
Solubility soluble in amyl acetate, alcohol, CCl4,[5] 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)[6]
Solubility in methyl acetate 7.81 g/100 g[5]
Solubility in ethyl acetate 10.7 g/100 g[5]
Vapor pressure 0.051 mPa (25 °C)[3]
1.08 kPa (200 °C)
28.06 kPa (300 °C)[7]
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[7]
452.37 J/mol·K[7]
-892 kJ/mol[7]
10030.6 kJ/mol[3]
Hazards
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)[2]
GHS signal word Warning
H319[2]
P305+351+338[2]
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oilHealth code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored 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).
N verify (what is YesYN ?)
Infobox references

Aluminium salts of palmitic acid and naphthenic acid were combined during World War II to produce napalm. The word "napalm" is derived from the words naphthenic acid and palmitic acid.

Contents

Occurrence and productionEdit

Palmitic acid was discovered by Edmond Frémy in 1840, in saponified palm oil.[10] This remains the primary industrial route for its production, with the triglycerides (fats) in palm oil being hydrolysed by high temperature water (above 200 °C or 390 °F), and the resulting mixture fractionally distilled to give the pure product.[11]

Palmitic acid is naturally produced by a wide range of other plants and organisms, typically at low levels. It is naturally present in butter, cheese, milk, and meat, as well as cocoa butter, soybean oil, and sunflower oil. The cetyl ester of palmitic acid (cetyl palmitate) occurs in spermaceti.

BiochemistryEdit

Excess carbohydrates in the body are converted to palmitic acid. 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,[12] and it is a major, but highly variable, lipid component of human breast milk.[13] 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.[14] In biology, some proteins are modified by the addition of a palmitoyl group in a process known as palmitoylation. Palmitoylation is important for membrane localisation of many proteins.

ApplicationsEdit

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 tree (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 "mouth feel" 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.[15] The aluminium salt is used as a thickening agent of napalm used in military actions.

Hydrogenation of palmitic acid yields cetyl alcohol, which is used to produce detergents and cosmetics.

Recently, a long-acting antipsychotic medication, paliperidone palmitate (marketed as INVEGA Sustenna), used in the treatment of schizophrenia, has been synthesized using the oily palmitate ester as a long-acting release carrier medium when injected intramuscularly. The underlying method of drug delivery is similar to that used with decanoic acid to deliver long-acting depot medication, in particular, neuroleptics such as haloperidol decanoate.

Health effectsEdit

According to the World Health Organization, evidence is "convincing" that consumption of palmitic acid increases the risk of developing cardiovascular disease,[16] based on studies indicating that it may increase LDL levels in the blood. Retinyl palmitate is an antioxidant and a source of vitamin A added to low fat milk to replace the vitamin content lost through the removal of milk fat. Palmitate is attached to the alcohol form of vitamin A, retinol, to make vitamin A stable in milk.

Rats fed a diet of 19% palmitic acid and 56% carbohydrate for extended periods showed alterations in central nervous system control of insulin secretion, and suppression of the body's natural appetite-suppressing signals from leptin and insulin (the key hormones involved in weight regulation).[17]

Palmitic acid strongly boosts metastasis in mouse models of human oral cancer cells. Among all fatty acids, it has the strongest effect in boosting the metastatic potential of CD36+ metastasis-initiating cells.[18][19]

See alsoEdit

ReferencesEdit

  1. ^ Merck Index, 12th Edition, 7128.
  2. ^ a b c d e f Sigma-Aldrich Co., Palmitic acid. Retrieved on 2014-06-02.
  3. ^ a b c d e f g CID 985 from PubChem
  4. ^ Palmitic acid at Inchem.org
  5. ^ a b c d http://chemister.ru/Database/properties-en.php?dbid=1&id=6488
  6. ^ Seidell, Atherton; Linke, William F. (1952). Solubilities of Inorganic and Organic Compounds. Van Nostrand. Retrieved 2014-06-02. 
  7. ^ a b c d 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), http://webbook.nist.gov (retrieved 2014-05-11)
  8. ^ 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. 
  9. ^ Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The Lipid Handbook with Cd-Rom. 3rd ed. Boca Raton: CRC Press, 2007. ISBN 0849396883 | ISBN 978-0849396885
  10. ^ Frémy, E. (1842). "Memoire sur les produits de la saponification de l'huile de palme". Journal de Pharmacie et de Chimie. XII: 757. 
  11. ^ 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. 
  12. ^ Kingsbury, K. J.; Paul, S.; Crossley, A.; Morgan, D. M. (1961). "The fatty acid composition of human depot fat". Biochemical Journal. 78: 541–550. PMC 1205373 . PMID 13756126. 
  13. ^ Jensen, RG; Hagerty, MM; McMahon, KE (June 1978). "Lipids of human milk and infant formulas: a review". Am. J. Clin. Nutr. 31: 990–1016. PMID 352132. 
  14. ^ Fatty acid biosynthesis - Reference pathway
  15. ^ US Soil Association standard 50.5.3
  16. ^ Diet, Nutrition and the Prevention of Chronic Diseases, WHO Technical Report Series 916, Report of a Joint WHO/FAO Expert Consultation, World Health Organization, Geneva, 2003, p. 88 (Table 10)
  17. ^ Benoit SC, Kemp CJ, Elias CF, Abplanalp W, Herman JP, Migrenne S, Lefevre AL, Cruciani-Guglielmacci C, Magnan C, Yu F, Niswender K, Irani BG, Holland WL, Clegg DJ (2009). "Palmitic acid mediates hypothalamic insulin resistance by altering PKC-θ subcellular localization in rodents". Journal of Clinical Investigation. 119 (9): 2577–2587. doi:10.1172/JCI36714. PMC 2735917 . PMID 19726875. 
  18. ^ Pascual, Gloria; et al. (7 December 2016). "Targeting metastasis-initiating cells through the fatty acid receptor CD36". Nature. doi:10.1038/nature20791. Retrieved 7 December 2016. 
  19. ^ Sánchez, Lucas (7 December 2016). "Descubiertas las células que inician la metástasis del cáncer" (in Spanish). El País. Retrieved 7 December 2016. 

External linksEdit

  Media related to Palmitic acid at Wikimedia Commons