One hundred and sixty-five grams (1.2 moles) of anhydrous zinc chloride (Note
1) is dissolved with the aid of heat in
165 g. (158 ml., 2.7 moles) of glacial acetic acid, which has been placed in a
1-l. beaker. To this hot mixture (about 140°),
110 g. (1 mole) of resorcinol is added with constant stirring. The solution is heated on a
sand bath until it
just begins to boil (about 152°). The flame is then removed and the reaction allowed to complete itself at a temperature not in excess of 159° (Note
2). After standing on the sand bath without further heating for 20 minutes, the solution is diluted with a mixture of
250 ml. of concentrated hydrochloric acid and 250 ml. of water. The dark red solution is placed in an
ice bath and cooled at 5°. The resulting precipitate is collected on a filter and washed free from zinc salts with
1 l. of dilute (1:3) hydrochloric acid in 200-ml. portions. This orange-red product, after drying, weighs
104–110 g. and melts at
141–143°. It is distilled under reduced pressure (Note
3), and boils at
180–181° at 10 mm. (
147–152° at 3–4 mm.). After most of the product has distilled, the temperature rises sharply, and the operation is discontinued when the temperature reaches 190°. The light-yellow distillate is removed from the
receiver with hot
ethanol and the
ethanol is evaporated (Note
4). This product weighs
100–106 g. It is further purified as follows: the substance is dissolved in
1.8 l. of hot dilute (1:11) hydrochloric acid, filtered hot, and cooled to 5°. The crystals are removed by filtration, washed with two 200-ml. portions of ice water, and dried. The yield of tan-colored
resacetophenone, melting at
142–144°, is
93–99 g. (
61–65%).