Citric acid

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Citric acid
Stereo skeletal formula of citric acid
Stereo skeletal formula of citric acid
Ball-and-stick model of citric acid
Ball-and-stick model of citric acid
Crystal sample from the saturated citric acid solution.
Names
IUPAC name
Citric acid[1]
Preferred IUPAC name
2-Hydroxypropane-1,2,3-tricarboxylic acid[1]
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.973 Edit this at Wikidata
EC Number
  • 201-069-1
E number E330 (antioxidants, ...)
KEGG
RTECS number
  • GE7350000
UNII
  • InChI=1S/C6H8O7/c7-3(8)1-6(13,5(11)12)2-4(9)10/h13H,1-2H2,(H,7,8)(H,9,10)(H,11,12) checkY
    Key: KRKNYBCHXYNGOX-UHFFFAOYSA-N checkY
  • InChI=1/C6H8O7/c7-3(8)1-6(13,5(11)12)2-4(9)10/h13H,1-2H2,(H,7,8)(H,9,10)(H,11,12)
    Key: KRKNYBCHXYNGOX-UHFFFAOYAM
  • OC(=O)CC(O)(C(=O)O)CC(=O)O
Properties
C6H8O7
Molar mass 192.123 g/mol (anhydrous), 210.14 g/mol (monohydrate)[2]
Appearance white solid
Odor Odorless
Density 1.665 g/cm3 (anhydrous)
1.542 g/cm3 (18 °C, monohydrate)
Melting point 156 °C (313 °F; 429 K)
Boiling point 310 °C (590 °F; 583 K) decomposes from 175 °C[3]
54% w/w (10 °C)
59.2% w/w (20 °C)
64.3% w/w (30 °C)
68.6% w/w (40 °C)
70.9% w/w (50 °C)
73.5% w/w (60 °C)
76.2% w/w (70 °C)
78.8% w/w (80 °C)
81.4% w/w (90 °C)
84% w/w (100 °C)[4]
Solubility Soluble in acetone, alcohol, ether, ethyl acetate, DMSO
Insoluble in C
6H
6, CHCl3, CS2, toluene[3]
Solubility in ethanol 62 g/100 g (25 °C)[3]
Solubility in amyl acetate 4.41 g/100 g (25 °C)[3]
Solubility in diethyl ether 1.05 g/100 g (25 °C)[3]
Solubility in 1,4-dioxane 35.9 g/100 g (25 °C)[3]
log P −1.64
Acidity (pKa) pKa1 = 3.13[5]
pKa2 = 4.76[5]
pKa3 = 6.39,[6] 6.40[7]
pKa4 = 14.4[8]
1.493–1.509 (20 °C)[4]
1.46 (150 °C)[3]
Viscosity 6.5 cP (50% aq. sol.)[4]
Structure
Monoclinic
Thermochemistry
226.51 J/(mol·K) (26.85 °C)[9]
252.1 J/(mol·K)[9]
−1543.8 kJ/mol[4]
1985.3 kJ/mol (474.5 kcal/mol, 2.47 kcal/g),[4] 1960.6 kJ/mol[9]
1972.34 kJ/mol (471.4 kcal/mol, 2.24 kcal/g) (monohydrate)[4]
Pharmacology
A09AB04 (WHO)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Skin and eye irritant
GHS labelling:
GHS05: CorrosiveGHS07: Exclamation mark[5]
Warning
H290, H319, H315[5]
P305+P351+P338[5]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
1
0
Flash point 155 °C (311 °F; 428 K)
345 °C (653 °F; 618 K)
Explosive limits 8%[5]
Lethal dose or concentration (LD, LC):
3000 mg/kg (rats, oral)
Safety data sheet (SDS) HMDB (PDF)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Citric acid is an organic compound with the skeletal formula HOC(CO2H)(CH2CO2H)2.[10] It is a colorless weak organic acid.[10] It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms.[10]

More than two million tons of citric acid are manufactured every year. It is used widely as acidifier, flavoring, preservative, and chelating agent.[11]

A citrate is a derivative of citric acid; that is, the salts, esters, and the polyatomic anion found in solutions and salts of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate. When citrate trianion is part of a salt, the formula of the citrate trianion is written as C
6H
5O3−
7 or C
3H
5O(COO)3−
3.

  1. ^ a b International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 747. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. ^ CID 22230 from PubChem
  3. ^ a b c d e f g "citric acid". chemister.ru. Archived from the original on November 29, 2014. Retrieved June 1, 2014.
  4. ^ a b c d e f CID 311 from PubChem
  5. ^ a b c d e f Fisher Scientific, Citric acid. Retrieved on 2014-06-02.
  6. ^ "Data for Biochemical Research". ZirChrom Separations, Inc. Retrieved January 11, 2012.
  7. ^ "Ionization Constants of Organic Acids". Michigan State University. Retrieved January 11, 2012.
  8. ^ Silva, Andre M. N.; Kong, Xiaole; Hider, Robert C. (2009). "Determination of the pKa value of the hydroxyl group in the α-hydroxycarboxylates citrate, malate and lactate by 13C NMR: implications for metal coordination in biological systems". BioMetals. 22 (5): 771–778. doi:10.1007/s10534-009-9224-5. ISSN 0966-0844. PMID 19288211.
  9. ^ a b c Citric 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 2014-06-02)
  10. ^ a b c "Citric acid | C6H8O7 - PubChem". Archived from the original on January 19, 2022. Retrieved December 19, 2021.
  11. ^ Apleblat, Alexander (2014). Citric acid. Springer. ISBN 978-3-319-11232-9.