When the solution has cooled to room temperature, stirring is started and
6.6 ml. of concentrated hydrochloric acid is added through the open neck of the flask, followed by
30 ml. of benzaldehyde from the dropping funnel. When the precipitate of
monobenzalpentaerythritol starts forming, dropwise addition of
benzaldehyde is begun (Note
4). After the addition of
benzaldehyde is completed, the mixture is stirred for an additional 3 hours (Note
5). The precipitate is collected (Note
6) on a
Büchner funnel and washed with ice-cold water which has been made slightly alkaline by addition of
sodium carbonate. The solid is transferred to a
3-l. round-bottomed flask, 1 l. of water (slightly alkaline with
sodium carbonate) is added, and the mixture is heated to 100° (Note
7). After about 10 minutes at this temperature the hot mixture is filtered quickly through a fluted filter paper (Note
8). The solid remaining on the filter paper is washed with 50 ml. of hot water (made slightly alkaline with
sodium carbonate) (Note
9). The combined aqueous filtrates are cooled in an
ice bath for several hours, and the crystals are collected on a Büchner funnel and dried. The dry product is heated under reflux for 15 minutes in an
Erlenmeyer flask with
200 ml. of toluene, and the hot mixture is allowed to cool to room temperature, with continuous agitation (
stirring rod) to prevent formation of hard lumps. Finally, the mixture is cooled in an
ice bath for 5 hours, and the solid product is collected on a Büchner funnel and dried (Note
10). The yield of
monobenzalpentaerythritol melting at
134–135° is
215–227 g. (
73–77%).