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Oxalic acid

Oxalic acid
Structural formula of oxalic acid
Skeletal formula of oxalic acid
Space-filling model of oxalic acid
Oxalic acid dihydrate
Names
Preferred IUPAC name
Oxalic acid
Systematic IUPAC name
Ethanedioic acid
Other names
Wood bleach
Identifiers
144-62-7 YesY
3D model (Jmol) Interactive image
3DMet B00059
385686
ChEBI CHEBI:16995 YesY
ChEMBL ChEMBL146755 YesY
ChemSpider 946 YesY
DrugBank DB03902 YesY
ECHA InfoCard 100.005.123
EC Number 205-634-3
2208
KEGG C00209 N
MeSH Oxalic+acid
PubChem 971
RTECS number RO2450000
UNII 9E7R5L6H31 YesY
UN number 3261
Properties
C2H2O4
Molar mass 90.03 g·mol−1
(anhydrous)
126.065 g mol−1 (dihydrate)
Appearance White crystals
Odor odorless
Density 1.90 g cm−3 (anhydrous)
1.653 g cm−3 (dihydrate)
Melting point 189 to 191 °C (372 to 376 °F; 462 to 464 K)
101.5 °C (214.7 °F; 374.6 K) dihydrate
143 g/L (25 °C)
Solubility 237 g/L (15 °C) in ethanol
14 g/L (15 °C) in diethyl ether
Vapor pressure <0.001 mmHg (20 °C)
Acidity (pKa) 1.25, 4.14
-60.05·10−6 cm3/mol
Pharmacology
QP53AG03 (WHO)
Hazards
Main hazards Toxic T
Safety data sheet External MSDS
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 166 °C (331 °F; 439 K)
Lethal dose or concentration (LD, LC):
1000 mg/kg (dog, oral)
1400 mg/kg (rat)
7500 mg/kg (rat, oral)
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 1 mg/m3
REL (Recommended)
TWA 1 mg/m3 ST 2 mg/m3
IDLH (Immediate danger)
500 mg/m3
Related compounds
Related compounds
oxalyl chloride
disodium oxalate
calcium oxalate
phenyl oxalate ester
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Oxalic acid is an organic compound with the formula C2H2O4. It is a colorless crystalline solid that forms a colorless solution in water. Its condensed formula is HOOCCOOH, reflecting its classification as the simplest dicarboxylic acid. Its acid strength is much greater than that of acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate (C
2
O2−
4
), is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate with the formula C2H2O4·2H2O. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.

The preparation of salts of oxalic acid from plants had been known, at the latest, since 1745, when the Dutch botanist and physician Herman Boerhaave isolated a salt from sorrel. By 1773, François Pierre Savary of Fribourg, Switzerland had isolated oxalic acid from its salt in sorrel.

In 1776, Swedish chemists Carl Wilhelm Scheele and Torbern Olof Bergman produced oxalic acid by reacting sugar with concentrated nitric acid; Scheele called the acid that resulted socker-syra or såcker-syra (sugar acid). By 1784, Scheele had shown that "sugar acid" and oxalic acid from natural sources were identical.

In 1824, the German chemist Friedrich Wöhler obtained oxalic acid by reacting cyanogen with ammonia in aqueous solution. This experiment may represent the first synthesis of a natural product.


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