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 C; 6H; 6, 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
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
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Citric acid is an organic compound with the chemical formula HOC(CO₂H)(CH₂CO₂H)₂. It is a colorless weak organic acid. 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.

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

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

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