Submitted by A. E. Osterberg
Checked by Frank C. Whitmore and H. C. Benedict, Jr.
1. Procedure
In a
600-cc. beaker 210 g. (0.88 mole) of ethyl bromomalonate (p. 245) (Note
1) and
165 g. (0.89 mole) of potassium phthalimide (p. 119) are intimately stirred together. The mixture is stirred approximately every ten minutes. If no spontaneous reaction starts within one-half hour (Note
1), it is necessary to initiate the reaction by heating to 110–120°. The mixture then becomes liquid and can be stirred easily. It turns to a light brown color, especially near the top where it comes in contact with the air. When the temperature begins to drop, the mixture is heated in an
oil bath at 110° for one hour to insure completion of the reaction.
The mixture is then poured into a
mortar where it solidifies to a solid mass (Note
2). When cold, the mixture is ground up with water to remove most of the
potassium bromide and filtered. The precipitate is then reground with water and refiltered, finally being washed well with water. The solid material on the filter consists of some
potassium bromide, some
phthalimide, and the
ethyl phthalimidomalonate. Without drying, it is put into a
1-l. flask with
400 cc. of benzene and heated to boiling. After cooling, the insoluble bromide and
phthalimide are removed by filtration. The filtrate contains some water, which is removed by means of a
separatory funnel.
The
benzene solution is dried with
20 g. of calcium chloride and the
benzene removed by distillation under diminished pressure on a
water bath. The residue is poured into a mortar where it solidifies. The crystalline mass is then ground with small amounts of
ether (200 cc. in all), filtered, and washed with
ether (about 100 cc.) until pure white. The yield of
ethyl phthalimidomalonate melting at
73–74° is
155–162 g. From the ether filtrate after distilling the
ether, there may be recovered a further amount by washing with a small amount of
ether to remove the brown color. The total weight of
ester obtained in the two crops is
180–190 g. (
67–71 per cent of the theoretical amount).
2. Notes
3. Discussion
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