3,5-Dihydroxybenzoic Acid → 3,5-Diacetoxybenzoic Acid

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Reaction Steps

3,5-Dihydroxybenzoic acid (77grams, 0.5 mole) and 200 milliliters of acetic anhydride were mixed in a five hundred milliliter round-bottomed flask, which was fitted with a reflux condenser. As the mixture was heated to reflux the dihydroxyacid went into solution. Refluxing was continued for a total of 5 hours. A brown solution was obtained. Excess acetic anhydride was removed by rotary evaporation and the remaining solid was dried under vacuum at 40° C. The solid was dissolved in about 200 milliliters of refluxing chloroform, filtered hot and then diluted with 70 milliliters of petroleum ether (bp 60°-80° C.). The compound crystallized overnight and was isolated by filtration and washed with a 1:1 mixture of petroleum ether and chloroform. The compound was then recrystallized by the same procedure. Yield was 59 grams (50%) of white crystals. Melting point was 157°-159° C. NMR conducted as in the preceeding preparation, but using (DMSO-d6) gave as peaks, in ppm: 2.1 (s,6H), 7.23 (s, 1H), 7.55 (s, 2H), 13.3 (b, 1H).

Provenance & Evidence