Palmitic acid

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Palmitic acid[1]
Palmitic acid.svg
Palmitic-acid-3D-balls.png
Identifiers
CAS number 57-10-3 YesY
PubChem 985
ChemSpider 960 N
ChEMBL CHEMBL82293 N
IUPHAR ligand 1055
Jmol-3D images Image 1
Properties
Molecular formula C16H32O2
Molar mass 256.42 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) [7]
Boiling point 351–352 °C (664–666 °F; 624–625 K) [8]
271.5 °C (520.7 °F; 544.6 K)
at 100 mmHg[2]
215 °C (419 °F; 488 K)
at 15 mmHg
Solubility in water 4.6 mg/L (0 °C)
7.19 mg/L (20 °C)
8.26 mg/L (30 °C)
9.9 mg/L (45 °C)
11.8 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) 4.78
Refractive index (nD) 1.43 (70 °C)[3]
Thermochemistry
Specific
heat capacity
C
463.36 J/mol·K[6]
Std molar
entropy
So298
452.37 J/mol·K[6]
Std enthalpy of
formation
ΔfHo298
-892 kJ/mol[6]
Std enthalpy of
combustion
ΔcHo298
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
GHS hazard statements H319[2]
GHS precautionary statements P305+351+338[2]
EU classification Irritant Xi
R-phrases R36/37/38
S-phrases S26
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 206 °C (403 °F; 479 K) [2]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

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

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.

Occurrence and production[edit]

Palmitic acid mainly occurs as its ester in triglycerides (fats), especially palm oil but also tallow. The cetyl ester of palmitic acid (cetyl palmitate) occurs in spermaceti. It was discovered by Edmond Frémy in 1840, in saponified palm oil.[10] Butter, cheese, milk and meat also contain this fatty acid.

Palmitic acid is prepared by treating fats and oils with water at a high pressure and temperature (above 200 °C or 390 °F), leading to the hydrolysis of triglycerides. The resulting mixture is then distilled.[11]

Biochemistry[edit]

Excess carbohydrates in the body are converted to palmitic acid. Palmitic acid is the first fatty acid produced during fatty acid synthesis and 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 comprise 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.

Applications[edit]

Palmitic acid is mainly used to produce soaps, cosmetics, and release agents. These applications utilize sodium palmitate, which is commonly obtained by saponification of palm oil. To this end, palm oil, rendered from the coconut palm nut, is treated with sodium hydroxide (in the form of caustic soda or lye), which causes hydrolysis of the ester groups. This procedure affords glycerol and sodium palmitate.

Because it is inexpensive and adds texture to processed foods (convenience food), palmitic acid and its sodium salt find wide use including foodstuffs. Sodium palmitate is permitted as a natural additive in organic products.[15] Salt of Alluminiun is as 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 effects[edit]

According to the World Health Organization, evidence is "convincing" that consumption of palmitic acid increases risk of developing cardiovascular diseases, placing it in the same evidence category as trans fatty acids.[16] 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 20% palmitic acid and 80% 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]

See also[edit]

References[edit]

  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 CID 985 from PubChem
  4. ^ a b c d http://chemister.ru/Database/properties-en.php?dbid=1&id=6488
  5. ^ Seidell, Atherton; Linke, William F. (1952). [Google Books Solubilities of Inorganic and Organic Compounds]. Van Nostrand. Retrieved 2014-06-02. 
  6. ^ a b c d n-Hexadecanoic acid in Linstrom, P.J.; Mallard, W.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)
  7. ^ 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. 
  8. ^ Palmitic acid at Inchem.org
  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. 
  13. ^ Lipids of human milk and infant formulas: a review
  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. PMID 19726875. 

External links[edit]