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834 Chapter 27
Copyright © 2017 Pearson Education, Inc.
20.
The polymer is stiffer because the OH on the middle carbon of glycerol cross-links the polymer chains.
HN
NH
CH
3
C OCH
2
CH
2
O
O
C NH
O
C
O
O
OCH
2
CHCH
2
O C
O
NH
NH
CH
3
NH
NH
NH
CH
3
C
O
OCH
2
CH
2
O C
CH
3
C
O
The polymer chains
are cross-linked.
O
21.
Formation of a protonated imine between formaldehyde and one amino group, followed by reaction with a
second amino group, accounts for formation of the linkage that holds the monomers together.
N N
N
NH
2
H
2
N
NH
2
H
2
C O
imine
formation
N N
N
NH
2
H
2
N
NH CH
2
+
N N
N
NH
2
H
2
N
NH
2
N N
N
NH
2
H
2
N
NHCH
2
NH
N N
N
NH
2
NH
2
a dimer of Melmac
(Occurs in
several steps;
see page 761 of
the text.)
+
−
H
+