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IUPAC name o-Phthalaldehyde
Other names o-Phthalic dicarboxaldehyde
CAS number 13283-31-3
RTECS number TH6950000
Molecular formula C8H6O2
Molar mass 134.13 g/mol
Appearance yellow solid
Melting point

55.5–56 °C

Solubility organic solvents
R-phrases 36/37/38
S-phrases 26-28-36
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

o-Phthalaldehyde is the chemical compound with the formula C6H4(CHO)2. Often abbreviated OPA, the molecule is a dialdehyde, consisting of two formyl (CHO) groups attached to adjacent carbon centres on a benzene ring. This pale yellow solid is a building block in the synthesis of heterocyclic compounds and a reagent in the analysis of amino acids.



The molecule was first described in 1887 when it was prepared from α,α,α',α’-tetrachloro-ortho-xylene.[1] A more modern synthesis is similar: the hydrolysis of the related tetrabromoxylene using potassium oxalate, followed by purification by steam distillation.[2] The reactivity of OPA is complicated by the fact that with water it forms both a mono- and dihydrate, C6H4(CHO)(CH2OH) and C6H4(CH2OH)2, respectively.[3]

Isomeric phthalaldehydes

Related to o-phthalaldehyde are the meta and para isomers, which are respectively named isophthalaldehyde (m.p. 87-88 °C, CAS# 626-19-7) terephthalaldehyde (m.p. 114-116 °C, CAS# 623-27-8).


  1. ^ Colson, A.; Gautier, H. "Nouveau Mode de Chloruration des Carbures" Annales de Chimie (Paris), 1887, volume 6, number 11, pp. 28.
  2. ^ Bill J. C.; Tarbell, D. S. “o-Phthalaldehyde” Organic Syntheses, Collected Volume 4, p.807 (1963).
  3. ^ Zuman, H. "Reactions of Orthophthalaldehyde with Nucleophiles" Chemical Reviews 2004; volume 104, pp. 3217-3238. doi:10.1021/cr0304424

External links

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Phthalaldehyde". A list of authors is available in Wikipedia.
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