Org. Synth. 1932, 12, 36
DOI: 10.15227/orgsyn.012.0036
ETHYL α,β-DIBROMO-β-PHENYLPROPIONATE
[Hydrocinnamic acid, α,β-dibromo-, ethyl ester]
Submitted by T. W. Abbott and Darrell Althousen.
Checked by Henry Gilman and G. F. Wright.
1. Procedure
In a
1-l. round-bottomed flask, provided with a
two-holed stopper fitted with a
dropping funnel and air-vent, is placed
176.2 g. (1 mole) of ethyl cinnamate (Org. Syn. Coll. Vol. I, 1941, 252) dissolved in
100 cc. of carbon tetrachloride (Note 1). The flask is placed in ice, and
159.8 g. (51.2 cc., 1 mole) of bromine is added in small quantities with frequent stirring
(Note 2).
After standing for one hour, the solution is poured into a large dish and the carbon tetrachloride and unused bromine allowed to evaporate spontaneously (Note 3). The dibromo ester separates in large crystals which form a solid cake in the bottom of the dish (Note 4). This cake is broken up and spread in a thin layer on a large Büchner funnel and subjected to suction until all traces of bromine have disappeared. The white crystals are then dried by pressing between large filter papers. The yield of crude dibromo ester is 280–285 g. (83–85 per cent of the theoretical amount). It melts at 65–71°.
If pure ester is desired, it may be obtained by recrystallizing from petroleum ether (b.p. 70–90°); the yield is 80–85 g. of ester melting at 74–75° from 100 g. of crude product.
2. Notes
1.
Carbon tetrachloride is used instead of
ether, which produces a very disagreeable lachrymator.
2.
The
bromine disappears rapidly at first, but more slowly at the end of the reaction. No
hydrogen bromide is evolved. The time of addition is about twenty to twenty-five minutes.
3.
This process is rather slow; it may be accelerated by inverting over the dish a
large funnel which is connected to a
suction pump. In this manner the crystalline cake separates in about two hours.
4.
If the reaction is carried out carefully, practically no mother liquor is left. However, if such liquor should remain it will yield, on evaporation, crystals which are impure and must be recrystallized before use.
3. Discussion
Ethyl α,β-dibromo-β-phenylpropionate is prepared by adding
bromine to
ethyl cinnamate.
1
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
petroleum ether
ether (60-29-7)
hydrogen bromide (10035-10-6)
bromine (7726-95-6)
carbon tetrachloride (56-23-5)
Ethyl cinnamate (103-36-6)
Ethyl α,β-dibromo-β-phenylpropionate,
Hydrocinnamic acid, α,β-dibromo-, ethyl ester (5464-70-0)
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