Question

Sketch a portion of a head-to-head, tail-to-tail, and a head-to-tail polymer made from acrylonitrile, \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCN}\).

Short answer

Answer: In a head-to-tail polymer of acrylonitrile, when two monomers are connected, the resulting structure is: \(\mathrm{H}_{2} \mathrm{C}-\mathrm{C}(\mathrm{CN})-\mathrm{CH}=\mathrm{C}\mathrm{H}_{2}\).

Step-by-step solution

Identify the functional groups in the monomer

Before we can draw the different types of polymers, we need to identify the head and tail of the monomer. In the acrylonitrile monomer, the head is the carbon atom with the hydrogen atoms (\(\mathrm{H}_{2} \mathrm{C}\)), and the tail is the carbon atom bonded to the cyano group (\(-\mathrm{CN}\)).

Sketch the head-to-head polymer

In a head-to-head polymer, the heads of the monomers are bonded to each other, and the tails are also bonded to each other. Draw two acrylonitrile monomers connected head-to-head, and tail-to-tail. The resulting structure will be: \(\mathrm{H}_{2} \mathrm{C}-\mathrm{C}(\mathrm{CN})=\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{C}(\mathrm{CN})\)

Sketch the tail-to-tail polymer

In a tail-to-tail polymer, the tails of the monomers are bonded to the head of the next monomer, and vice versa. Draw two acrylonitrile monomers connected tail-to-tail: \(\mathrm{C}(\mathrm{CN})-\mathrm{CH}=\mathrm{C}\mathrm{H}_{2}-\mathrm{CH}=\mathrm{C}(\mathrm{CN})\) Remember that in tail-to-tail polymer, the polymer chain will end with the head of a monomer connected to the tail of another monomer.

Sketch the head-to-tail polymer

In a head-to-tail polymer, the head of one monomer is bonded to the tail of the next monomer. Draw two acrylonitrile monomers connected head-to-tail: \(\mathrm{H}_{2} \mathrm{C}-\mathrm{C}(\mathrm{CN})-\mathrm{CH}=\mathrm{C}\mathrm{H}_{2}\) Notice that in this polymer, the chain will continue by connecting the head of another monomer to the tail of the last monomer.