A tared, 500-ml., two-necked, round-bottomed flask is equipped with a magnetic stirring bar, a thermometer, and an ice-filled cooling bath. A solution of 13.5 g. (0.100 mole) of 4-aminoacetophenone (Note 1) in 200 ml. of acetone is placed in the flask and stirred while 32 ml. (about 0.3 mole) of aqueous 48% hydrobromic acid is added. After the resulting solution has been cooled to 5–7°, it is stirred continuously while 20 ml. of an aqueous solution containing 6.90 g. (0.100 mole) of sodium nitrite is added rapidly (30 seconds) beneath the surface of the reaction solution with a hypodermic syringe or a long-stemmed dropping funnel. Stirring and cooling are continued until the exothermic reaction subsides (Note 2) and the reaction solution has cooled to 14–15°. After 106 g. (100 ml., 1.47 moles) of acrylic acid (Note 3) is added, the solution is again cooled to 14–15°, with stirring, before 0.10–0.11 g. (0.00069–0.00077 mole) of copper(I) bromide (Note 4) is added. Stirring is continued, during which time the solution darkens, and nitrogen evolution is observed; the temperature of the reaction mixture is kept below 33° by use of the external cooling bath. As soon as the evolution of nitrogen has ceased (usually 20 minutes is sufficient), the reaction solution is concentrated with a rotary evaporator, giving a mixture weighing about 120–130 g. The residual brown suspension is mixed with 5 g. of decolorizing charcoal and 200 ml. of water, and the resulting mixture is boiled for 3 minutes, and filtered while hot through a Büchner funnel containing Celite filter aid. The residue on the filter is washed with 100 ml. of boiling water, and the combined filtrates are diluted with 300 ml. of water. The resulting aqueous solution, from which the product begins to crystallize, is cooled in a water bath and then allowed to stand in a refrigerator (0–3°) for 24 hours to complete the crystallization of the crude product. The crystalline solid is collected on a filter, washed with two 100-ml. portions of cold water, and dried in the air. The crude product, a pale yellow solid (19.1–22.2 g.), is recrystallized from 40 ml. of a 2:3 (v/v) formic acid-water mixture. The resulting crystals are collected on a filter, washed with 20 ml. of 2:3 (v/v) cold formic acid-water, and dried in the air, yielding 16.6–18.2 g. (61–67%) of white needles, m.p. 158–160°, which are sufficiently pure for most purposes. Three additional crystallizations from 20-ml. portions of 2:3 (v/v) formic acid-water give 15.2–16.0 g. (56–59%) (Note 5) of the pure p-acetyl-α-bromohydrocinnamic acid, m.p. 159–161° (Note 6).