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)^Y

Key: KRKNYBCHXYNGOX-UHFFFAOYSA-N^Y
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

192.12 g·mol⁻¹

Appearance

crystalline 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

117.43 g/100 mL (10 °C)
147.76 g/100 mL (20 °C)
180.89 g/100 mL (30 °C)
220.19 g/100 mL (40 °C)
382.48 g/100 mL (80 °C)
547.79 g/100 mL (100 °C)

Solubility

soluble in alcohol, ether, ethyl acetate, DMSO
insoluble in C₆H₆, 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 (pK_a)

pKa₁ = 3.13
pKa₂ = 4.76
pKa₃ = 6.39, 6.40

Refractive index (n_D)

1.493–1.509 (20 °C)
1.46 (150 °C)

Viscosity

6.5 cP (50% aq. sol.)

Structure

Crystal structure

Monoclinic

Thermochemistry

Specific
heat capacity (C)

226.51 J/(mol·K) (26.85 °C)

Std molar
entropy (S^o₂₉₈)

252.1 J/(mol·K)

Std enthalpy of
formation (Δ_fH^o₂₉₈)

−1548.8 kJ/mol

Std enthalpy of
combustion (Δ_cH^o₂₉₈)

−1960.6 kJ/mol
−1972.34 kJ/mol (monohydrate)

Pharmacology

ATC code

A09AB04 (WHO)

Hazards

Main hazards

skin and eye irritant

Warning

GHS hazard statements

H319

GHS precautionary statements

P305+351+338

EU classification (DSD)

R-phrases

R34, R36/37/38, R41

S-phrases

S24/25, S26, S36/37/39, S45

NFPA 704

Flash point

155 °C (311 °F; 428 K)

Autoignition
temperature

345 °C (653 °F; 618 K)

Explosive limits

Lethal dose or concentration (LD, LC):

LD₅₀ (median dose)

3000 mg/kg (rats, oral)

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

(what is ^YN ?)

Infobox references

Citric acid is a weak organic tricarboxylic acid having the chemical formula C₆H₈O₇. 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 a million tons of citric acid are manufactured every year. It is used widely as an acidifier, as a flavoring and 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 ion is written as C₆H₅O₇³⁻ or C₃H₅O(COO)₃³⁻.

Citric acid exists in greater than trace amounts in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have particularly high concentrations of the acid; it can constitute as much as 8% of the dry weight of these fruits (about 47 g/L in the juices). The concentrations of citric acid in citrus fruits range from 0.005 mol/L for oranges and grapefruits to 0.30 mol/L in lemons and limes. Within species, these values vary depending on the cultivar and the circumstances in which the fruit was grown.

Industrial-scale citric acid production first began in 1890 based on the Italian citrus fruit industry, where the juice was treated with hydrated lime (calcium hydroxide) to precipitate calcium citrate, which was isolated and converted back to the acid using diluted sulfuric acid. In 1893, C. Wehmer discovered Penicillium mold could produce citric acid from sugar. However, microbial production of citric acid did not become industrially important until World War I disrupted Italian citrus exports.

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Wikipedia