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The Royal Society of Chemistry"

Methanolysis of phthalic anhydride

SyntheticPage 428

DOI: 

Submitted: July 1, 2010, published: July 5, 2010

Authors

Christopher Cooksey (rsc@chriscooksey.demon.co.uk)

A contribution from 

Reaction Scheme

Chemicals

phthalic anhydride (Aldrich)
methanol

Procedure

Powdered phthalic anhydride (74 g, 0.5 mol) and methanol (100 cm3, 2.47 mol) were heated under reflux with magnetic stirring on an oil bath for 8 h. The clear solution was distilled to remove most of the methanol. Toluene (100 cm3) was added to the residue and distillation was continued until the still-head temperature reached 110 ºC. After cooling to 30 ºC, the resulting thick white precipitate was filtered and the residue washed with toluene (50 cm3). Petroleum ether (30/40, 100 cm3) was added to the combined filtrates to give a dense oil which crystallised as long white needles after standing overnight. Filtration and washing with petroleum ether (60/80, 50 cm3) gave the product, 44.5 g, 49% yield.

Author Comments

A subsequent perusal of the literature reveals a much simpler procedure, 0.5 h reflux and no toluene: "Under a nitrogen atmosphere, a mixture of 75.0 grams (0.506 mole) of phthalic anhydride in 120.0 grams (3.75 moles) of methanol was stirred and heated under reflux for 30 minutes. During this time a complete solution was attained. The reaction mixture was concentrated under reduced pressure to a residual oil. The oil was placed in a refrigerator where it solidified to yield when dried, 93.0 grams of phthalic acid, mono-methyl ester; m.p. 80-81.5 ºC." in quantitative yield.

Chang Jun H, Baum J S, US 4892578 (9 Jan 1990)

Data

δH (CDCl3, 200 MHz) 7.68m (1H), 7.61m (1H), 7.56m (2H), 3.92s (3H)

Lead Reference

E L Eliel, A W Burgstahler, J Amer Chem Soc, 1949, 71, 2251-2252. doi: 10.1021/ja01174a509

Other References

Chang Jun H, Baum J S, US 4892578 (9 Jan 1990)

Keywords

addition, alcohols, carboxylic acids, esters, nucleophilic