Citric acid
Not to be confused with Vitamin C.
Citric acid


IUPAC 3-carboxy-3-hydroxy pentanedioic acid
other name2-hydroxypropane- 1,2,3- tricarboxylic acid
3-hydroxypentanedioic acid-3-carboxylic acid
Hydrogen citrate
Identifiers
CAS number 77-92-9 Y
PubChem 311
ChemSpider 305
SMILES [show]
O=C(O)CC(O)(C(=O)O)CC(=O)O
InChI [show]
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)
InChI key KRKNYBCHXYNGOX-UHFFFAOYAM
Properties
Molecular formula C6H8O7
Molar mass 192.124 g/mol (anhydrous)
210.14 g/mol (monohydrate)
Appearance crystalline white solid
Density 1.665 g/cm3
Melting point 153 °C

Boiling point decomposes at 175 °C

Solubility in water 133 g/100 ml (22°C)
Solubility in THF, ethanol, methanol anhydrous: THF 1.80 M, ethanol 1.6 M, methanol 3.08 M [1]
monohydrate: THF 1.52 M, ethanol 1.78 M, methanol 2.27 M [2]
Acidity (pKa) pKa1=3.15
pKa2=4.77
pKa3=6.40
Hazards
Main hazards skin and eye irritant
Flash point ?°C
Related compounds
Related compounds sodium citrate, calcium citrate
Y (what is this?) (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references
Citric acid is a weak organic acid, and it is a natural preservative and is also used to add an acidic, or sour, taste to foods and soft drinks. In biochemistry, it is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of virtually all living things. It can also be used as an environmentally benign cleaning agent.

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[3]). 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.