In a
1-l. distilling flask, fitted with a side arm 40 cm. in length and not less than 10 mm. in internal diameter (Note
1), is placed
236 g. (2 moles) of succinic acid. To this is added slowly, with cooling and shaking,
270 cc. (243 g., 4 moles) of 28 per cent aqueous ammonia (sp. gr. 0.90). Most of the acid dissolves, forming a clear solution. The flask is set for downward distillation, and a
water-cooled 500-cc. distilling flask is attached to the side arm. Provision may be made for removal of
ammonia from the side tube of the
receiver. The mixture is heated gently over a free flame; solution takes place rapidly, and a small amount of uncombined
ammonia passes over with the first portions of the distillate. The temperature of the vapor rises to 100° and remains at this point until about 200 cc. of water has distilled. The flame is then increased, and the
ammonium succinate begins to decompose with evolution of
ammonia; the temperature of the vapor falls to 97° during the distillation of the next 30 cc. When the vapor temperature has risen to 102°, the receiver is changed and an intermediate fraction collected from 102° to 275°.
Succinimide then distils and is collected over the range
275–289°, largely at
285–289°. Decomposition takes place to a small extent with formation of a black tar; the distillation is stopped when the tarry residue begins to decompose with evolution of yellow fumes.
The crude
succinimide, which solidifies completely, amounts to about
168 g. The intermediate fraction is redistilled from a smaller flask and furnishes about
10 g. more of crude
succinimide boiling between 275° and 289°. The two portions of crude
succinimide are combined and crystallized from
95 per cent ethyl alcohol, employing 1 cc. of solvent for every gram of product. If the mixture is chilled to 0° for some hours before filtration and about
25 cc. of cold alcohol is employed for washing the crystals, the first crop amounts to
163–164 g. (
82–83 per cent of the theoretical amount). On concentrating the mother liquor to one-third of its volume, a second crop of
4–5 g. can be secured (Note
2). The product melts at
123–125° and contains no water of crystallization.