Organic Syntheses | Page 5

E. M. CHADWELL. Checked by H. T.
CLARKE and R. P. LEAVITT.
1. Procedure
A SOLUTION of 218 g. of sodium hydroxide in 1960 g. of water and
1000 g. of 95 per cent alcohol are introduced into a 5500-cc. bottle
which is loosely covered with a perforated disk of cardboard, supplied
with an effective stirrer, and supported in a larger vessel so as to permit
cooling with cracked ice. Into the alkaline solution, 520 g. of pure
acetophenone is poured, the bottle is rapidly surrounded with cracked
ice, and the stirrer started; 460 g. of benzaldehyde (U. S. P.) are then
added at once. The temperature of the mixture should not be below 15'0
and it should not be allowed to rise above 30'0 during the reaction. If it
tends to do so, the stirring is not sufficiently vigorous.
It is advantageous, though not essential, to inoculate the mixture with a
little powdered benzalacetophenone after stirring for half an hour. After
two to three hours, the mixture becomes so thick that the stirring is no
longer effective. The stirrer is then removed and the mixture left to
itself in an ice-box for about ten hours. The mixture now is a thick
paste composed of small shot-like grains suspended in an almost
colorless liquid. It is cooled in a freezing mixture and then either
centrifuged or filtered on a large Buchner funnel, washed with water
until the washings are neutral to litmus, and finally washed with 200 cc.
of alcohol, which has previously been cooled to 0'0. After thorough
drying in the air, the crude product weighs about 880 g. (yield 97 per
cent of the theoretical amount) and melts at 50-54'0. It is sufficiently
pure for most purposes but tenaciously holds traces of water. It is most
readily purified by recrystallization from four to four and a half times
its weight of 95 per cent alcohol. Eight hundred and eighty grams of
crude product give 770 g. (85 per cent of the theoretical amount) of
light-yellow material (m. p. 55-57'0) and 40-50 g. that require
recrystallization.
2. Notes

The acetophenone should be as pure as possible (m. p. 20'0).
Commercial acetophenone contains variable quantities of impurities
which reduce the yield. By distilling commercial acetophenone with the
help of a good still-head (preferably under diminished pressure) and
using only the fraction which boils at 201-202'0 (76-77'0/10 mm.)
greater quantities of benzalacetophenone can be obtained than by using
the entire sample.
Commercial benzaldehyde can be used in place of the purer product,
but the amount used must be increased to make up for the impurities
which are present.
If the temperature is too low, or the stirring too slow, the product
separates as an oil, which later solidifies in large lumps.
If the temperature is allowed to rise above 30'0, secondary reactions
diminish both the yield and the purity of the product. The most
favorable temperature is 25'0.
In recrystallizing benzalacetophenone, the alcohol should be saturated
at 50'0. If the solution is saturated above this temperature, the
benzalacetophenone tends to separate as an oil. The solution should be
allowed to cool gradually, and should finally be chilled in a freezing
mixture. 3. Other Methods of Preparation
The methods for producing benzalacetophenone are: the action of acids
on a mixture of benzaldehyde and acetophenone or on a solution of
these substances in glacial acetic acid;[1] the condensation of
benzaldehyde and acetophenone with a 30 per cent solution of sodium
methylate at low temperatures;[2] the action of sodium hydroxide on an
alcoholic solution of benzaldehyde and acetophenone.[3]
The methods based on the use of acids as condensing agents were not
considered, because Claisen, who devised them, abandoned them after
he found that alkaline condensing agents gave better results. The
preliminary experiments showed that condensation with sodium
methylate takes a long time and gives a product which it is difficult to
handle in large quantities. The method devised by Kostanecki and
Rossbach[3] has therefore been developed.
[1] Ber. 14, 2463 (1881).
[2] Ber. 20, 657 (1887).
[3] Ber. 29, 1492 (1896).

II
BENZYL BENZOATE
2 C6H5CHO + C6H5CH2ONa--> C6H5CO2CH2C6H5 +
C6H5CH2ONa
Prepared by O. KAMM and W. F. KAMM. Checked by ROGER
ADAMS and R. L. JENKINS.
1. Procedure
THREE grams of metallic sodium are dissolved by warming for half an
hour in 70 g. of pure benzyl alcohol (see notes), and after the mixture
has cooled to room temperature the solution is added gradually, with
thorough mixing, to 454 g. of c. p. benzaldehyde (which must contain
LESS than 1 per cent of benzoic acid). The reaction mixture has a
tendency to become warm, but the temperature should be kept slightly
below 50-60'0 by cooling, if necessary. A pasty gelatinous mass results.
After about half an hour the temperature of the mixture no longer rises;