Chemistry Reference
In-Depth Information
-cresol, and
subsequent extraction with hydrochloric acid to remove the suspended inorganic matter [
237
], yields
a material that is still only soluble in pyridine and
Hydrolysis in water of the product of acetylation, followed by treatment with hot
m
-cresol.
Somewhat similar results are obtained in reductions of high molecular weight poly(methyl
acrylate) with lithium aluminum hydride [
238
] in tetrahydrofuran. The reaction yields a product
that is only soluble in mixtures of hydrochloric acid with either methyl alcohol, dioxane, or
tetrahydrofuran. The problem is apparently due to some residual aluminum that is hard to remove
[
239
]. If, however, the reduction is carried out in a
m
-methylmorpholine solution, followed by
addition of potassium tartrate, a pure product can be isolated [
240
].
N
N
-methylmorpholine is a good
solvent for reductions of various macromolecules with metal hydrides [
236
]. In addition, the solvent
permits use of strong NaOH solutions to hydrolyze the addition complexes that form. Other polymers
that can be reduced in it are those bearing nitrile, amide, imide, lactam, and oxime pendant groups.
Reduction of polymethacrylonitrile, however, yields a product with only 70% of primary amine
groups [
241
].
Complete reductions of pendant carbonyl groups with LiAlH
4
in solvents other than
-
methylmorpholine, however, were reported. Thus, a copolymer of methyl vinyl ketone with styrene
was fully reduced in tetrahydrofuran [
242
].
Reductions with metal hydrides are often preliminary steps for additional reactions. For instance, a
product of LiAlH
4
reduction of syndiotactic poly(methyl methacrylate) can be reacted with succinic
anhydride and then converted to an amide [
243
]:
N
O
O
O
LiAlH
4
O
O
O
OH
O
OH
2
O
RNH
2
O
O
NHR
2
O
Substituted succinic anhydride can be used as well. When poly(dimethyl itaconate) is reduced with
LiAlH
4
in THF, the product contains some ash, but 93% of the functional groups are reduced [
239
]:
OH
O
O
LiAlH
4
+
O
O
OH
