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.