Chemistry Reference
In-Depth Information
When chloromethylated cross-linked polystyrene is reacted with potassium superoxide, the yield
depends upon the type of solvent used. In dimethylsulfoxide, in the presence of 18-crown-6 ether,
the conversion to hydroxymethyl groups is 45%. In benzene, however, it is only 25%. High
conversions are obtained by catalyzing the reaction with tetrabutylammonium iodide in a mixture
of solvents. This results in 85% conversions to hydroxymethyl groups, while the rest become iodide
groups [
199
].
Quaternary salts are more effective than crown ethers in reactions with salts of oxygen-anions,
such as carboxylate and phenolate [
200
]. On the other hand, lipophilic crown ethers, like
dicyclohexyl-18-crown-6, exhibit higher catalytic activity than the quaternary salts in reactions
with salts of the sulfur anions. Also, the catalytic activity of the phase transfer catalysts toward
nitrogen anions is intermediate between that toward oxygen and that toward sulfur anions.
Solid-liquid two-phase systems generally give higher degrees of conversion than do liquid-liquid
systems. When, however, lipophilic phase transfer catalysts are used with lipophilic reagents, high
degrees of substitutions are achieved in liquid-liquid two-phase systems [
200
].
Conversion of chloromethylated styrene to anionic exchange resins is done commercially by
amination reactions to form quaternary ammonium groups [
201
,
202
]. This reaction can be illustrated
as follows [
203
]:
N(CH
3
)
3
+
CH
2
Cl
Cl
N
HN(CH
3
)
2
ClCH
2
CH
2
OH
N
HCl
N
Cl
OH
The kinetics of amination of chloromethylated polystyrene with monohydroxy dialkyl tertiary
amines shows that the reactions proceed in two steps, at two different rates. The rate changes take
