A.
Cyclohexylidenecyanoacetic acid. The
benzene solution is diluted with an additional
100 ml. of hot benzene and transferred to a
1-l. separatory funnel. The solution is allowed to cool until it is slightly above room temperature, and then
200 ml. of ether is added, small portions being used to rinse the reaction flask. After the solution has cooled to room temperature, it is washed with two 50-ml. portions of cold water (Note
5). The emulsion which normally forms at this point is broken by slow filtration through a
Büchner funnel. The
ether is removed, and the
benzene solution is concentrated to approximately 300 ml. by distillation under reduced pressure. The solution is allowed to cool slowly to room temperature and then is cooled to about 10° in a refrigerator (Note
6).
Cyclohexylidenecyanoacetic acid crystallizes as colorless prisms (Note
7). It is collected on a Büchner funnel, washed with two
100-ml. portions of cold benzene (10°), and dried in a
vacuum desiccator to constant weight (
88–92 g.). The filtrate and washings are concentrated by distillation under reduced pressure to about 150 ml. and cooled as in the first crystallization. The second crop of crystals is separated by filtration, washed with two
50-ml. portions of cold benzene (10°), and dried in a vacuum desiccator to constant weight (
21–25 g.). Further concentration of the mother liquor and washings to a volume of about 75 ml. followed by cooling, filtering, washing with two
10-ml. portions of cold benzene, and drying yields an additional
2–5 g. The total yield of
cyclohexylidenecyanoacetic acid, m.p.
110–110.5°, is
108–126 g. (
65–76%).