The condensation of acetone using anhydrous hydrogen chloride results after three weeks at room temperature, in a 15% yield of phorone (4) and a 75% yield of mesityl oxide (5). In the presence of one weight percent of the Lewis acid, aluminium chloride, the yield of 4 is increased to 39%. An increase in the amount of the Lewis acid, aluminium chloride, to ten weight percent results in a 22% yield of phorone (4) and a 68% yield of mesityl oxide (5). In the presence of one hundred weight percent

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... f aluminium chloride, in the absence of hydrogen chloride, the condensation produces a 62% yield of mesityl oxide (5) and no phorone (4). In the course of this investigation, two intermediates, 6 and 7 were isolated and characterized for the first time. These intermediates are the actual products formed in the condensation of acetone with hydrogen chloride, and not the "free" phorone (4) and mesityl oxide (5). The conversion of 6 and 7 to 5 and 4, respectively, occurs during the isolation stage using a saturated solution of ethanolic potassium hydroxide.