Maleic acid

From Wikipedia, the free encyclopedia

Maleic acid
Skeletal formula of maleic acid
Ball-and-stick model of the maleic acid molecule
Space-filling model of the maleic acid molecule
IUPAC name Maleic acid
(Z)-Butenedioic acid
Identifiers
CAS number [110-16-7]
EINECS number 203-742-5
RTECS number OM9625000
SMILES OC(=O)C=CC(=O)O
Properties
Molecular formula C4H4O4
Molar mass 116.1 g/mol
Appearance white solid
Density 1.59 g/cm³, solid
Melting point

131-139°C decomposes

Boiling point

135 °C decomp.

Solubility in water 78 g/100 ml (25 °C)
Acidity (pKa) pka1 = 1.97, pka2 = 6.07
Hazards
MSDS MSDS from J. T. Baker
EU classification Harmful (Xn)
R-phrases R22, R36/37/38
S-phrases (S2), S26, S28, S37
Related compounds
Related dicarboxylic acids Fumaric acid
Succinic acid
Related compounds Maleic anhydride
Maleimide
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Maleic acid or (Z)-butenedioic acid or cis-butenedioic acid or malenic acid or maleinic acid or toxilic acid is an organic compound that is a dicarboxylic acid (molecule with two carboxyl groups). The molecule consists of an ethylene group flanked by two carboxylic acid groups. Maleic acid is the cis isomer of butenedioic acid, whereas fumaric acid is the trans isomer. The cis isomer is the less stable one of the two; the difference in heat of combustion is 22.7 kJ/mol. The physical properties of maleic acid are very different from those of fumaric acid. Maleic acid is soluble in water, whereas fumaric acid is not; and the melting point of maleic acid (130 - 139 °C) is also much lower than that of fumaric acid (287 °C). Both properties of maleic acid can be explained on account of the intramolecular hydrogen bonding[1] that takes place at the expense of intermolecular interactions.

Maleic acid should not be confused with malic acid or malonic acid, both of which are different types of dicarboxylic acids. In biology the compound goes by the name ionised maleate.

Contents

[edit] Synthesis

In industry, maleic acid is derived from maleic anhydride by hydrolysis. Maleic anhydride is produced from benzene or butane in an oxidation process.

[edit] Reactions

[edit] Maleates

The maleate ion is the ionised form of maleic acid. It is of importance to biochemistry. The maleate ion is useful in biochemistry as an inhibitor of transaminase reactions. Maleic acid esters are also called maleates, for instance dimethyl maleate.

[edit] References

  1. ^ M. N. G James, G. J. B Williams (1974). "A Refinement of the Crystal Structure of Maleic Acid". Acta Crystallographica B30 (5): 1249–1275. doi:10.1107/S0567740874004626. 
  2. ^ Light isomerization experiment (from the University of Regensburg, with video)
  3. ^ DSM glyoxylic acid production
  4. ^ Catalytic Hydrogenation of Maleic Acid at Moderate Pressures A Laboratory Demonstration Kwesi Amoa 1948 Journal of Chemical Education • Vol. 84 No. 12 December 2007

[edit] External links

Wikimedia Commons has media related to: