Question

$CH\equiv CH\underset{\Delta }{\overset{C{u}_{2}C{l}_2/N{H}_{4}Cl}{\to }}A\stackrel{HCl}{\to }B$
When B is polymerized, what is not true about the polymer?

• A. Polymer formed is 1,4-addition polymer
• B. Polymer formed is known as polyisoprene
• C. Polymer formed is known as synthetic rubber
• D. Polymer formed is poly-2-chlorobuta-1,3-diene

Answer 1

The correct option is B Polymer formed is known as polyisoprene

$CH\equiv CH\underset{\Delta }{\overset{C{u}_{2}C{l}_2/N{H}_{4}Cl}{\to }}\underset{\left(A\right)}{C{H}_2=CH-C\equiv CH}\stackrel{HCl}{\to }\underset{\left(B\right)}{H_{2}C=CH-\underset{\stackrel{|}{Cl}}{C}=C{H}_2}$
Acetylene dimerises to give vinyl acetylene, which is then combined with $HCl$ to afford 4-chloro-1,2-butadiene (B), which in the presence of copper(I) chloride, rearranges to the targeted 2-chlorobuta-1,3-diene.
Polymerisation of B (chloroprene) yields neoprene, a synthetic rubber which is formed by 1,4-addition.