Furfuryl dimethyl amine is first produced, This may conveniently be
accomplished by employing the Leuckart synthesis known to those skilled in
the art, which involves the use of an aldehyde or a ketone, and formate of
ammonia or an amine, or corresponding formamide derived by dehydration of
formate of ammonia or an amine.
For example, 5 mols of dimethyl amine and 5 mols of formic acid and water
are distilled to 135°C; distilling off most of the water. To the remaining liquid,
consisting for the most part of the formyl derivative of dimethyl amine, 1 mol
of furfural mixed with 1 mol of formic acid is slowly added with heating, the
temperature being maintained at 150°C to 170°C, until the reaction is
complete. The mixture is then distilled into a receiver. The course of this
reaction may be illustrated as follows:
Part of the formic acid used in the above reaction functions to react with the
dimethyl amine liberated in the reaction.
After the furfural has all been added and the reaction has subsided, the
residue is cooled, diluted with water, made strongly alkaline and distilled until
all volatile substances are removed, The distillate is then made acid with
formic acid and distilled with steam as long as nonbasic substances are
carried over by the steam. The residue is then made strongly basic with
caustic soda and the volatile amines again distilled with steam. The distillate
is then treated with strong alkali and then extracted with ether to extract the
base. The extract is dried by the addition of caustic potash, the ether removed
and the residual amine purified by distillation. Furfuryl dimethyl amine boils
over the range 145°C to 150°C.
To obtain the quaternary salt, furfuryl dimethyl amine so prepared is dissolved
in dry benzene and to the solution is added slightly more than one equivalent
of methyl iodide. Inducement of crystallization of the quaternary salt which
separates may be effected as, for example, by scratching the side of the
vessel containing the mixture or seeding with a small quantity of the
crystalline quaternary salt.
