Citric acid

Citric acid
Names
	IUPAC name Citric acid
	Preferred IUPAC name 2-Hydroxypropane-1,2,3-tricarboxylic acid
Identifiers
CAS Number	77-92-9 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:30769 ;
ChEMBL	ChEMBL1261 ;
ChemSpider	305 ;
DrugBank	DB04272 ;
ECHA InfoCard	100.000.973
EC Number	201-069-1;
E number	E330 (antioxidants, ...)
IUPHAR/BPS	2478;
KEGG	D00037 ;
PubChem CID	311; 22230 (monohydrate);
RTECS number	GE7350000;
UNII	XF417D3PSL ;
CompTox Dashboard (EPA)	DTXSID3020332 ;
	InChI 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) Key: KRKNYBCHXYNGOX-UHFFFAOYSA-N ; 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;
	SMILES OC(=O)CC(O)(C(=O)O)CC(=O)O;
Properties
Chemical formula	C6H8O7
Molar mass	192.123 g/mol (anhydrous), 210.14 g/mol (monohydrate)
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
Solubility in water	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)
Solubility	Soluble in acetone, alcohol, ether, ethyl acetate, DMSO; Insoluble in benzene, CHCl3, CS2, toluene
Solubility in ethanol	62 g/100 g (25 °C)
Solubility in amyl acetate	4.41 g/100 g (25 °C)
Solubility in diethyl ether	1.05 g/100 g (25 °C)
Solubility in 1,4-dioxane	35.9 g/100 g (25 °C)
log P	−1.64
Acidity (pKa)	pKa1 = 3.13; pKa2 = 4.76; pKa3 = 6.39, 6.40; pKa4 = 14.4
Refractive index (nD)	1.493–1.509 (20 °C); 1.46 (150 °C)
Viscosity	6.5 cP (50% aq. sol.)
Structure
Crystal structure	Monoclinic
Thermochemistry
Heat capacity (C)	226.51 J/(mol·K) (26.85 °C)
Std molar; entropy (S⦵298)	252.1 J/(mol·K)
Std enthalpy of; formation (ΔfH⦵298)	−1543.8 kJ/mol
Heat of combustion, higher value (HHV)	1985.3 kJ/mol (474.5 kcal/mol, 2.47 kcal/g), 1960.6 kJ/mol; 1972.34 kJ/mol (471.4 kcal/mol, 2.24 kcal/g) (monohydrate)
Pharmacology
ATC code	A09AB04 (WHO)
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Skin and eye irritant
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H290, H319, H315
Precautionary statements	P305+P351+P338
NFPA 704 (fire diamond)	2 1 0
Flash point	155 °C (311 °F; 428 K)
Autoignition; temperature	345 °C (653 °F; 618 K)
Explosive limits	8%
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	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). Infobox references

Citric acid is an organic compound with the formula C₆H₈O₇.^[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.

^ ^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.
^ CID 22230 from PubChem
^ ^a ^b ^c ^d ^e ^f ^g "citric acid". chemister.ru. Archived from the original on November 29, 2014. Retrieved June 1, 2014.
^ ^a ^b ^c ^d ^e ^f CID 311 from PubChem
^ ^a ^b ^c ^d ^e ^f Fisher Scientific, Citric acid. Retrieved on 2014-06-02.
^ "Data for Biochemical Research". ZirChrom Separations, Inc. Retrieved January 11, 2012.
^ "Ionization Constants of Organic Acids". Michigan State University. Retrieved January 11, 2012.
^ 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.
^ ^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)
^ ^a ^b ^c "Citric acid | C6H8O7 - PubChem". Archived from the original on January 19, 2022. Retrieved December 19, 2021.
^ Apleblat, Alexander (2014). Citric acid. Springer. ISBN 978-3-319-11232-9.

[IUPAC2014-1] 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

[chemister-3] ^ ^a ^b ^c ^d ^e ^f ^g "citric acid". chemister.ru. Archived from the original on November 29, 2014. Retrieved June 1, 2014.

[pubchem-4] ^ ^a ^b ^c ^d ^e ^f CID 311 from PubChem

[sigma-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.

[Silva_Kong_Hider_2009_pp._771–778-8] 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.

[nist-9] 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)

[Pubchem-10] "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.

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