A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Page
GO
GO
?
^
Top
Org. Synth. 1968, 48, 51
DOI: 10.15227/orgsyn.048.0051
CINNAMYL BROMIDE
[Benzene, 3-bromopropenyl-]
Submitted by John P. Schaefer, J. G. Higgins, and P. K. Shenoy1.
Checked by R. Breslow and J. T. Groves.
1. Procedure
A 1-l., three-necked, round-bottomed flask equipped with a Trubore stirrer, a pressure-equalizing dropping funnel, and a reflux condenser with a drying tube is charged with 350 ml. of acetonitrile (Note 1) and 106.4 g. (0.41 mole) of triphenylphosphine (Note 2). The flask is cooled in an ice-water bath (Note 3), and 64 g. (0.40 mole) of bromine is added dropwise over a period of ca. 15–20 minutes (Note 4) and (Note 5). The ice-water bath is removed, and a solution of 54 g. (0.40 mole) of cinnamyl alcohol in 50 ml. of acetonitrile is added in portions over a period of 5–10 minutes with continued stirring (Note 6). The solvent is removed by distillation with the use of a water aspirator (30–40 mm.) and an oil bath until the bath temperature reaches 120°. The water aspirator is replaced by a vacuum pump and the water-cooled condenser with an air condenser, and the distillation is continued with rapid stirring (Note 7), (Note 8), and (Note 9). Most of the product (Note 10) distills at 91–98° (2–4 mm.), and about 59 g. of product crystallizes in the receiving flask (63–75% yield) (Note 11).
The product is dissolved in 200 ml. of ether, and the solution is washed with 75 ml. of saturated aqueous sodium carbonate, dried over anhydrous magnesium sulfate, and distilled to give 47–56 g. (60–71%) of product, b.p. 66–68° (0.07 mm.), 84–86° (0.8 mm.); m.p. 29°.
2. Notes
1. The acetonitrile was distilled from phosphorus pentoxide.
2. Triphenylphosphine was obtained from M and T Chemicals, Inc., and used without further purification.
3. The triphenylphosphine is only partially dissolved.
4. If a slight excess of bromine persists after addition, a small amount of triphenylphosphine should be added until the color of bromine disappears.
5. The solid triphenylphosphine disappears, but at the same time the adduct, (C6H5)3PBr2, precipitates as a white solid.
6. This addition is mildly exothermic, and the temperature rises to 50–60°. All the precipitate should dissolve at this point; warming by external heat may be necessary.
7. To protect the vacuum pump from damage a dry ice-acetone trap and two liquid nitrogen traps are necessary to condense and solidify the hydrogen bromide evolved.
8. The receiving flask is placed in an ice-water bath.
9. The distillation is continued until the triphenylphosphine oxide solidifies and no more product distills. The oil bath is maintained at 130–140° during the distillation.
10. Some product is carried over by the hydrogen bromide in the initial stages of the distillation.
11. When this distillation was replaced by a procedure in which the acetonitrile was removed with a rotary evaporator and steam bath, and the product was extracted from the triphenylphosphine oxide with small portions of acetonitrile totaling ca. 250 ml., the checkers obtained an improved yield (79%) of cinnamyl bromide.
3. Discussion
Cinnamyl bromide has been prepared from cinnamyl alcohol by the action of hydrogen bromide in cold acetic acid2 and of phosphorus tribromide in boiling benzene.3 It has also been prepared by the action of N-bromosuccinimide on 3-phenylpropene4 and on 1-phenylpropene.5
4. Merits of the Preparation
The method described is general for converting alcohols to alkyl halides and is stereospecific.6
This preparation is referenced from:

References and Notes
  1. Department of Chemistry, The University of Arizona, Tucson, Arizona 85721.
  2. J. von Braun and Z. Kohler, Ber., 51, 79 (1918).
  3. M. Gredy, Bull. Soc. Chim. France, [5] 3, 1098 (1936).
  4. M. Lora-Tomayo, F. Martin-Panizo, and R. P. Ossorio, J. Chem. Soc., 1418 (1950); E. A. Braude and E. S. Waight, J. Chem. Soc., 1116 (1952).
  5. O. A. Orio, Rev. Fac. Cienc. Quim., Univ. Nacl. La Plata, 30, 21 (1957) [C.A., 54, 12062 (1960)].
  6. L. Horner, H. Oediger, and H. Hoffmann, Ann., 626, 26 (1959); G. A. Wiley, R. L. Hershkowitz, B. M. Rein, and B. C. Chung, J. Am. Chem. Soc., 86, 964 (1964); J. P. Schaefer and D. S. Weinberg, J. Org. Chem., 30, 2635 (1965).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

acetic acid (64-19-7)

Benzene (71-43-2)

ether (60-29-7)

acetonitrile (75-05-8)

hydrogen bromide (10035-10-6)

sodium carbonate (497-19-8)

bromine (7726-95-6)

phosphorus tribromide (7789-60-8)

1-phenylpropene

magnesium sulfate (7487-88-9)

cinnamyl alcohol (104-54-1)

N-bromosuccinimide (128-08-5)

3-phenylpropene (300-57-2)

triphenylphosphine (603-35-0)

Cinnamyl bromide,
Benzene, 3-bromopropenyl- (4392-24-9)

triphenylphosphine oxide (791-28-6)

phosphorus pentoxide (1314-56-3)