Question

Write the name of monomers used for getting the following polymers:
(i) Bakelite (ii) Neoprene.

Answer 1

Hint: Polymers are the materials made up of long, repeating chains of molecules. The polymers have unique properties, depending on the type of monomers being used for the formation of polymers.

Complete step by step solution:
(i) Bakelite: It is a copolymer made up of phenol and formaldehyde. Phenol – Formaldehyde resins are obtained by the reaction of phenol and formaldehyde in the presence of a basic catalyst. The reaction involves the formation of methylene bridges in ortho, para or both ortho and para positions of phenol. When the polymerisation of these substituted phenols take place, result into the formation of a linear polymer called Novalac which is used in paints. The reaction for this polymerisation is given below,

Novalac on heating with $HCHO$undergo cross linkage to form an infusible solid called bakelite.

$\therefore $Monomers of bakelite are phenol and formaldehyde
(ii) Neoprene: Its monomer chloroprene is prepared from acetylene
\[\mathop {2CH \equiv CH}\limits_{acetylene} \mathop {\xrightarrow[{N{H_4}Cl}]{{C{u_2}C{l_2}}}}\limits_{\left( {343K} \right)} \mathop {{H_2}C = CH - C \equiv CH}\limits_{\left( {vinylacetylene} \right)} \xrightarrow{{HCl}}\mathop {{H_2}C = CH - C \equiv C{H_2}}\limits_{\left( {Chloroprene} \right)} \]
Chloroprene undergoes free radical polymerization to form neoprene. It polymerizes very rapidly and the reaction occurs by $1,{\text{ 4}}$- addition of one chloroprene to another.

Note: Neoprene was the first synthetic rubber manufactured on a large scale. It is also called diprene. The properties of neoprene are similar to natural rubber but neoprene is more resistant to action of oils, gasoline and other hydrocarbons. It is non – inflammable. Bakelite is used for making combs, fountain pens, electrical goods, etc. Soft Bakelite with low degree of polymerisation are used as binding glue for laminated, wooden plants and lacquers. Sulphonated bakelites are used as ion exchange resins.