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

Participants

Reaction Conditions

Reaction Steps

Terephthalic acid (10 kg) is charged into a reactor. Oleum (20% (18-24% SO3); 6 kg/kg terephthalic acid ) is added and then paraformaldehyde (1.33 equivalents, 0.24 kg/kg terephthalic acid) is added. The mixture is agitated at 125° C. for 17 hours. Water (13 kg/kg terephthalic acid and filter aid is added, the temperature is adjusted to about 70° C. The precipitate is filtered of, washed with water and suspended in water. The pH of the suspension is adjusted to about 7 with NaOH, activated carbon, 0.07 kg/kg terephthalic acid is added, and then the mixture is filtered, the precipitate is rinsed with water. The temperature of the filtrate is adjusted to about 65° C. and the pH is adjusted to about 2 with 50% sulfuric acid. The 5-carboxyphthalide precipitated is separated by filtration washed and dried. Yield 83%.

Provenance & Evidence