B.
Coumarilic acid. In a
5-l. three-necked flask fitted with a mechanical stirrer and
reflux condenser,
450 g. (8 moles) of solid potassium hydroxide is dissolved in
700 ml. of absolute ethanol. The solution is cooled to 15° by immersing the flask in an
ice bath, and
215 g. (0.7 mole) of finely divided coumarin dibromide is added in 10- to 15-g. portions to the well-stirred basic solution. The rate of addition is controlled so that the temperature never rises above 20°; the addition requires about 30 minutes. After all the dibromide has been added, the reaction mixture is refluxed, with stirring, for 30 minutes (Note
7). One and a half liters of water is added, and the resulting solution is steam-distilled until 2.5 l. of distillate has been collected (Note
8). The residue is cooled to room temperature by the addition of 1 kg. of cracked ice (Note
9) and is then acidified by the addition of
1.2 l. of 6 N hydrochloric acid. The crude
coumarilic acid is collected on a filter and stirred with 600 ml. of cold water. The acid is separated from the water by filtration, sucked as dry as possible on the filter, and then crystallized from a mixture of
250 ml. of ethanol and 250 ml. of water (Note
10). The recrystallized coumarilic acid is colorless, weighs
93–100 g. (
82–88%) (Note
11), and melts at
190–193°.