Question

In the natural rubber ‘Caoutchouc’, the isoprene units are joined by

• A. Head-to-head
• B. Tail-to-tail
• C. Head-to-tail
• D. All of these

Answer 1

Answer: (C)

Head-to-tail

Answer 2

$\overset{\text{Head}}{CH_{2}} = \underset{CH_{3}}{\underset{|}{C -}}CH = \overset{\text{Tail}}{CH_{2}} + ⥂ \overset{\text{Head}}{CH_{2}} = \underset{CH_{3}}{\underset{|}{C - CH}} = \overset{\text{Tail}}{CH_{2}} \rightarrow$

$( - CH_{2} - \underset{CH_{2}}{\underset{|}{C =}CH} - CH_{2} - CH_{2} - \underset{CH_{3}}{\underset{|}{C =}CH} - CH_{2} - )_{n}$

From steric effects, the polymer formed has head to tail configuration.