Benzoic Acid → Phenethyl Benzoate

Participants

Reaction Conditions

Reaction Steps

A 2-L, 4-neck round bottom flask, fitted with a thermometer, mechanical stirrer, nitrogen inlet tube and Liebig condenser/receiving flask, was charged with 671.7 g (5.50 mol, 1.00 equiv) of benzoic acid, 806.3 g (6.60 mol, 1.20 equiv) of 2-phenylethyl alcohol, and 1.25 g (0.1% w/w) of Fascat 2001®. The system was heated gently with slow stirring (<50 rpm) until the benzoic acid dissolved. The air was removed with three cycles of evacuation/nitrogen fill using a mechanical vacuum pump (50–100 torr). The rate of stirring was increased to ca. 200 rpm, the nitrogen sparge was set at 0.2 scfh, and the reaction mixture was heated to 180° C. After a 1 -h hold, the temperature was increased to 190° C. for 1 h and then to 200° C. for 1 h. The temperature was increased to 210° C. and the nitrogen sparge was increased to 0.5 scfh. After a 1-h hold, the temperature was further increased to 220° C. for 1 h. The total amount of distillate was 159.2 g, from which 94.4 g of water (theor. 99.1 g) was separated as the top layer. The reaction mixture was cooled to room temperature and sampled for analysis. The acid number was 1.10 mg KOH/g (99.7% conversion) and the APHA color was 115. The excess 2-phenylethyl alcohol (5.5% by GLC) was removed by vacuum distillation. Thus, after 1 h at 180–190° C. and 20 torr (0.5 scfh nitrogen sweep), the residual 2-phenylethyl alcohol was <0.05% by GLC and the APHA color was 222. Activated carbon (37.3 g, 3% w/w) was added, and the mixture was heated at 75–80° C. under vacuum (50–70 torr) for 1 h. After cooling to room temperature, filtration through Celite® gave 1100 g (90%) of 2-phenylethyl benzoate. The APHA color was 20, the acid number was 0.14 mg KOH/g, the saponification number was 246 mg KOH/g (theor. 248), and the residual tin was <10 ppm.

Provenance & Evidence