To a flask equipped with a dropping funnel, mechanical stirrer, and a 40 cm long side arm of not less than 10 mm inside diameter is added 236 gm (2.0 mole) of succinic acid. The flask is cooled and 270 ml (4.0 moles) of 28% aqueous ammonia is slowly added with stirring. The flask is rapidly heated with an oil bath until 200 ml of water distils. The temperature of the bath is rapidly raised to 275°C. Succinimide starts to distil over the range 275-289°C, to afford 168 gm of crude product which solidifies on cooling. The intermediate fraction, boiling between 102° and 275°C, is redistilled to afford 10.0 gm of crude succinimide, b.p. 275-289°C. The combined product (178 gm) is added to 178 gm of hot ethanol. The solution is cooled, the crystals filtered, washed with 25 ml of cold ethanol, and dried to afford 163-164 gm (82-83%), m.p. 123-125°C. Approximately 4-5 gm of additional product may be obtained by concentrating the mother liquor.
Recent Japanese patents suggested inert aprotic solvents such as cyclic amides (e.g., N-methylpyrrolidone, N-acetyl-2-pyrrolidone, DMF, or tet-ramethylurea) and azeotroping solvents (e.g., toluene, 0-xylene, hexane, or pentane) or other high-boiling solvents (e.g., chlorobenzene or chlo-rotoluene) as dehydrating agents for the formation of imides from dibasic acids (e.g., 3- and/or 4) hydroxyphthalic acid with a large variety of diamines including diaminosiloxanes such as bis (3-aminopropyl)-tetra-methylsiloxane.
