Org. Synth. 1953, 33, 70
[Acrylic acid, 2,3-diphenyl-]
Submitted by Robert E. Buckles and Keith Bremer1
Checked by T. L. Cairns and J. C. Lorenz.
In a 500-ml. round-bottomed flask
are placed 40.5 ml. (42.4 g., 0.40 mole) of freshly purified benzaldehyde (Note 1)
, 54.6 g. (0.40 mole) of phenylacetic acid
,2 40 ml. of anhydrous triethylamine (Note 2)
, and 80 ml. of acetic anhydride (Note 3)
. The mixture is boiled gently under reflux for 5 hours. After the heating period is over, the 500-ml. flask containing the reaction mixture is incorporated into a steam-distillation apparatus (Note 4)
. The reaction mixture is distilled with steam until the distillate coming over is no longer cloudy, and then about 50 ml. more of the distillate is collected. The distillate can be discarded. The aqueous residue is cooled, and the solution is then separated from the solid by decantation. The solid is dissolved in 500 ml. of hot 95% ethanol
, and 500 ml. of water, including the solution originally decanted from the crude solid, is added to the hot solution. The mixture is heated to boiling, and 2 g. of decolorizing carbon
is added. The hot solution is filtered, and the filtrate is immediately acidified to Congo red with 6N hydrochloric acid
. The solution is cooled, and the resulting crystals are removed from the mixture by filtration. The yield of crude α-phenylcinnamic acid
(m.p. around 161–165°
) is 60–67 g.
The product is purified by crystallization from aqueous ethanol (Note 5)
. The over-all yield of purified product, m.p. 172–173°
, is 48–53 g.
). The product is the isomer with the two phenyl groups cis
to each other since decarboxylation yields cis-stilbene3
(see p. 857
, suitable for this synthesis, is purified in the following way. A 60-g. (58-ml.) sample is washed with two 20-ml. portions of 10% sodium carbonate
and then with water. It is then dried over 5–10 g. of anhydrous magnesium sulfate
. A few small crystals of hydroquinone
are added with the drying agent. The dry benzaldehyde
is decanted through a cotton plug into a Claisen flask
; it is distilled under reduced pressure, preferably below 30 mm.
Sharples anhydrous grade triethylamine
was used without further purification.
The acetic anhydride
is carefully fractionated; the 137–139° fraction is collected.
A simple steam-distillation apparatus such as that given by Fieser4
is entirely satisfactory. It is usually necessary to heat the distillation flask with a steam bath
or a small flame in order to minimize the accumulation of excess water in the flask.
The submitters used 5 ml. of 95% ethanol
and 5 ml. of water per gram of crude product for recrystallization. The checkers found use of 3:2 ethanol:water by volume more convenient.
has been prepared by the distillation of benzylmandelic acid
by the condensation of phenylacetyl chloride6
or phenylacetic acid7
in the presence of triethylamine
; by the reaction of sodium or potassium phenylacetate
in acetic anhydride
and by the treatment of ethyl α-bromo-α,β-diphenylpropionate
with potassium hydroxide
The most convenient synthesis appears to be that described above.13,14,15
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
sodium or potassium phenylacetate
hydrochloric acid (7647-01-0)
acetic anhydride (108-24-7)
sodium carbonate (497-19-8)
decolorizing carbon (7782-42-5)
potassium hydroxide (1310-58-3)
Phenylacetic acid (103-82-2)
magnesium sulfate (7487-88-9)
phenylacetyl chloride (103-80-0)
Acrylic acid, 2,3-diphenyl- (3368-16-9)
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