Chemistry Reference
In-Depth Information
An acid-catalyzed exchange reaction of glycols and acetals yields polyacetals as follows:
R'
n
R
R
+
R'
n
HO
OH
+
2nROH
O
O
O
O
n
These reactions often lead to cyclic acetals that interfere with the formation of high molecular
weight products. Useful polyacetals, however, can be formed from pentaerythritol and acetals of
dialdehydes:
HO
R'O
R
OR'
n
HO
OH
+
n
R'O
OR'
HH
OH
O
O
R
n
O
O
Acetals generally exhibit poor resistance to hydrolytic attack. Some, however, are much more
resistant than others, depending upon the glycol. The following formal was reported to exhibit good
hydrolytic stability under both acidic and basic conditions [
109
]:
O
O
n
Pentaerythritol yields spiro polymers by this reaction. The products offer superior thermal
resistance [
114
]:
HO
O
O
+
n
O
O
n
HO
OH
O
O
n
OH
The addition of diols to dialkenes can be illustrated on addition of a glycol to a divinyl ether:
H
R'
O
O
n
+
HO
OH
n
R
R
O
O
O
R'
n
