Pinacolone → 4-Chlorobenzoic Acid

Participants

Reaction Conditions

Reaction Steps

In a 100 gallon stainless steel reactor was charged pinacolone (154.5 kg, 94% pure, 1453 moles), methyltributylammonium chloride (1.09 kg, 75% aqueous solution, 3.47 moles) and water (2.23 kg) and the reactor contents were heated to 40° C. Melted p-chlorobenzaldehyde (109.1 kg, 97.5% pure, 757.1 moles) addition was then started at a rate of 1.82 kg/min (the complete addition therefore took 60 minutes). Ten minutes after the start of the addition of the aldehyde, NaOH (12.36 kg, 50 wt % aqueous solution, 154.5 moles) addition was started at a rate of 0.41 kg/min (the complete addition therefore took 30 minutes). After the addition of the aldehyde was complete, the reactor temperature was increased to 60° C. and heated at that temperature for 3 hours. At that point analysis of the reaction mixture by LC (after negecting the pinacolone and a small amount of p-chlorobenzoic acid formed by air oxidation of the p-chlorobenzaldehyde) indicated that the organic phase contained 96.3% Phenyl aldol and 0.3% unreacted p-chlorobenzaldehyde. The reaction mixture was neutralized with 36% aqueous hydrochloric acid till pH 8.0 and the phases were allowed to settle. The aqueous (lower) phase was discarded and the organic phase was subjected to distillation under reduced pressure to recover all the excess pinacolone. The residue (166.1 kg) was the product Phenyl aldol and was found to be 96.8% pure which translates to a yield of 95.4% based on p-chlorobenzaldehyde.

Provenance & Evidence