In a
500-ml. round-bottomed three-necked flask fitted with a
reflux condenser, a
dropping funnel, and a
mercury-sealed stirrer (Note
1) is placed a solution of
46 g. (0.5 mole) of dry aniline in
125 ml. of pure dry benzene. Stirring is started, and a solution of
42 g. (0.5 mole) of ketene dimer (p. 508) in
75 ml. of pure dry benzene is added dropwise over a period of 30 minutes. The reaction mixture is then heated under reflux on the
steam bath for 1 hour. After the major portion of the
benzene has been removed by distillation from the steam bath, the remainder is removed under reduced pressure. The residue is dissolved in
500 ml. of hot 50% aqueous ethanol from which the
acetoacetanilide separates on cooling. The mixture is cooled to 0° before filtration. A second crop of crystals can be obtained by adding 250 ml. of water to the mother liquor and cooling again (Note
2). The total yield of product, m.p.
82–83.5°, is
65 g. (
74%). Further purification by recrystallization from
300 ml. of 50% ethanol yields
55 g. of a product that melts at
84–85°.