Formaldehyde → 1,3-Dihydro-1-oxoisobenzofuran-5-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

A solution of terephthalic acid (30 g) in oleum (20-25% SO3, 70 ml) is heated to 150° C. To this solution is added a solution of paraformaldehyde (8.8 g) in oleum (20-25% SO3, 37 ml) over a period of 1-2h. The reaction mixture is stirred at 150° C. for additional 4 h and cooled to 90° C. Water (190 ml) is added to the mixture at a rate so that the temperature stays below 100° C. The precipitate is filtered of, washed with hot (90-95° C.) water and suspended in water (200 ml) and dicalite (1.1 g) is added. The pH of the suspension is adjusted to about 7 with NaOH (approximately 60 ml) and activated carbon (1.1 g) is added. The mixture is filtered and the precipitate is rinsed with water. The temperature of the filtrate is adjusted to about 85° C., and the pH is adjusted to about 2 with sulphuric acid (96%, approximated 8 ml). The 5-carboxyphthalide precipitated is separated by filtration and dried.

Provenance & Evidence