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; it is then warmed on the water bath for about one or two hours, with occasional shaking.

The cooled reaction product is treated with 200 cc. of water, the layer of oil separated, washed once with a second portion of water, and subjected to distillation _in vacuo_. The first fraction of the distillate contains benzyl alcohol together with unchanged aldehyde, as well as a small quantity of water. The temperature then rises rapidly to the boiling-point of benzyl benzoate, when the receivers are changed. The product boils at 184-185'0/15 mm., and analysis by saponification shows it to consist of 99 per cent ester. A yield of 410-420 g. is obtained, which corresponds to 90-93 per cent of the theoretical amount. This benzyl benzoate supercools readily, but after solidifying melts within one degree of the highest recorded value (19.4'0) and therefore need not be refractionated, unless material of exceptional grade is required.

2. Notes

In the presence of sodium benzylate two molecules of benzaldehyde react with the alcoholate to form an addition product. When the reaction mixture is overheated an important side reaction may occur, as follows:

/ OCH2C6H5 C6H5C -- OCH2C6H5 --> C6H5CO2Na + C6H5CH2OCH2C6H5 \ ONa

Dibenzyl ether no doubt forms the chief impurity in benzyl benzoate. Since the boiling-point of the former lies near that of the ester,