4-Hydroxybenzoic Acid → 4-Hydroxy-N-(4-nitrophenyl)benzamide

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p-Hydroxybenzoic acid (59.05 grams, 0.4275 mole), sodium ethoxide catalyst (0.133 gram, 0.225% wt. of the p-hydroxybenzoic acid used) and N,N'-dimethylacetamide solvent (404 grams) are added to a reactor equipped with a reflux condenser and stirred under a nitrogen atmosphere at 80° C. p-Nitrophenylisocyanate (73.85 grams, 0.450 mole) is initially added in an aliquot of 25.00 grams, followed by 25.00 and 23-85 gram aliquots eleven then nine minutes later, respectively, and so as to maintain a 80° to 82° C. reaction temperature. After the last aliquot of p-nitrophenylisocyanate is added, heating of the reactor commenced and a 160° C. reaction temperature is achieved 24 minutes later. After three hours at the 160° C. reaction temperature, the reactor is cooled to 30° C. then the contents poured into one gallon of deionized water. A precipitated yellow powder is recovered via filtration of the aqueous slurry then dissolved into 1900 milliliters of boiling methanol and refluxed therein (65° C.). After cooling the methanol solution to 5° C. and maintaining therein for twelve hours, a first crop of pale yellow colored crystalline product is filtered off and dried at 110° C. under vacuum to a constant weight of 92.5 grams (79.6% isolated yield). No attempt was made to recover a second crop of crystalline product from the mother liquor. Fourier transform infrared spectrophotometric analysis of a nujol mull of a portion of the product on a sodium chloride plate revealed the presence of the expected secondary amide N--H stretching (solid state) at 3385 cm-1 (sharp), the secondary amide carbonyl stretching (solid state) at 1655 cm-1 (sharp), the hydroxyl group O--H stretching centered at 3232 cm-1 (broad) and the conjugated nitro group absorbances at 1537 and 1339 cm-1 (sharp). Proton magnetic resonance spectroscopy (250 MHz) further confirmed the product structure as -hydroxy-4'-nitrobenzanilide.

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