About 40 grams (0.223 mol) of p-acetylaminobenzoic acid was dissolved in
600 ml of absolute methanol, and the solution was heated to reflux
temperature. Heating was discontinued, and, with mechanical stirring, 19.9
grams (0.223 mol) of 2-dimethylaminoethanol was added through a dropping
funnel as fast as the exothermic nature of the reaction permitted. The
reaction mixture was allowed to cool to room temperature (2.5-3 hours)
under mechanical agitation, and the solution was suction-filtered through
Celite filter aid. The filtrate was poured into 500 ml of anhydrous ethyl ether,
seeded with a few crystals of 2-dimethylaminoethanol p-acetylaminobenzoate.
The seeding crystals were obtained by introducing 3 to 6 drops of the filtered
reaction mixture into a test tube containing 10 ml of anhydrous diethyl ether.
The contents of the test tube were thoroughly shaken and allowed to stand at
room temperature. The salt crystallized out within not more than 10-15
minutes.
The crude product (48.4 grams, 80.9% yield) was recrystallized from an
absolute ethanol-ethyl acetate solvent system by suspending the salt in
boiling anhydrous ethyl acetate and just enough absolute ethanol was
gradually added to effect solution after which the solution was concentrated to
about two-thirds of the original volume on the steam bath, charcoal treated,
and suction-filtered through Celite filter aid. The white crystals of 2-
dimethylaminoethanol p-acetylaminobenzoate obtained, dried at room
temperature at a pressure of 0.08 mm Hg for 15 hours, melted at 159.0°-
161.5°C.
