In a
3-l. three-necked flask equipped with a
mechanical stirrer, a
dropping funnel, a
reflux condenser, and a
thermometer are placed
110 g. (138 ml., 2 moles) of propionitrile (Note
1) and
8 g. (4.35 ml.) of concentrated sulfuric acid (sp. gr. 1.84). To the stirred mixture, which is heated to 90°, is added gradually a solution of
60 g. of trioxane (equivalent to 2 moles of
formaldehyde) in
110 g. (138 ml., 2 moles) of propionitrile. During the addition the temperature of the reaction mixture is kept between 95° and 105° (Note
2). When the addition is complete (30 to 60 minutes) (Note
3) the reaction mixture is heated under reflux for an additional 3 hours, the internal temperature being kept at approximately 105°. The mixture is then allowed to cool to room temperature; during the cooling period the product crystallizes. The light-brown crystals are collected by filtration with suction on a
Büchner funnel (Note
4). The solid (1
60 to 170 g.) is washed three times with
100-ml. portions of ether and air-dried. The crude yellow product (
130 to 135 g., melting point between
164° and 170°) is recrystallized from
160 ml. of 90% ethanol. The product is collected on a Büchner funnel, washed on the funnel with
100 ml. of ether, and air-dried. In this way
105 to 115 g. (
62 to 68%) of white crystals of
hexahydro-1,3,5-tripropionyl-s-triazine melting at
170–172° is obtained (Note
5). Recrystallization from
95% ethanol (2.4 ml. per g.) results in
91% recovery of an analytically pure product, m.p.
173.2–174.1° (cor.).