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Question: Which polymer has ‘chiral’ monomer(s)? A. PHBV B. Nylon 6,6 C. Buna-N D. Neoprene...

Which polymer has ‘chiral’ monomer(s)?
A. PHBV
B. Nylon 6,6
C. Buna-N
D. Neoprene

Explanation

Solution

The term ‘chiral’ is used to describe the object that is non-superimposable on its mirror image. And polymer is a substance or a material composed of many repeating subunits called monomers. For checking chirality in your compound, the presence of chiral center or chiral carbon is very important.

Complete step-by-step answer:
In a chiral molecule, there is a chiral center. Chiral centers are tetrahedral atoms, mostly carbons, that have four different substituents.
In the given question, there are four polymers which are PHBV; Nylon 6,6; Buna-N; Neoprene. The structures of these polymers are as follows,
1.PHBV: (−O−CHCH3−CH2−CO−O−CHC2H5−CH2−CO−)n{\left( { - O - CHC{H_3} - C{H_2} - CO - O - CH{C_2}{H_5} - C{H_2} - CO - } \right)_n}
2.Nylon 6,6: [−CO(CH2)4CO−NH(CH2)6NH−]n{\left[ { - CO{{\left( {C{H_2}} \right)}_4}CO - NH{{\left( {C{H_2}} \right)}_6}NH - } \right]_n}
3.Buna-N: [−CH2−CH=CH−CH2−CH(CN)−CH2−]n{\left[ { - C{H_2} - CH = CH - C{H_2} - CH\left( {CN} \right) - C{H_2} - } \right]_n}
4.Neoprene: (−CH2−CH=CCl−CH2−)n{\left( { - C{H_2} - CH = CCl - C{H_2} - } \right)_n}
The monomers that are the subunits of the above polymers are as follows,
1.PHBV: CH3−CHOH−CH2−COOHC{H_3} - CHOH - C{H_2} - COOH which is called 3-hydroxybutanoic acid and CH3−CH2−CHOH−CH2−COOHC{H_3} - C{H_2} - CHOH - C{H_2} - COOH which is called 3-hydroxypentanoic acid are the two monomers of PHBV.
2.Nylon 6,6: HO2C−(CH2)4−CO2HH{O_2}C - {\left( {C{H_2}} \right)_4} - C{O_2}H which is called adipic acid and H2N−(CH2)6−NH2{H_2}N - {\left( {C{H_2}} \right)_6} - N{H_2}which is called hexamethylenediamine are the two polymers of Nylon 6,6.
3.Buna-N: CH2=CH−CH=CH2C{H_2} = CH - CH = C{H_2} which is called 1,3-butadiene and CH2(CN)=CH2C{H_2}\left( {CN} \right) = C{H_2}which is called acrylonitrile are the two polymers of Buna-N.
4.Neoprene: CH2=CH−CCl=CH2C{H_2} = CH - CCl = C{H_2} which is called chloroprene is the polymer of Neoprene.
From the above-mentioned monomers, we can see that only in PHBV, also known as Poly(3-hydroxybutyrate-co-3-hydroxyvalerate), both the monomers are chiral compounds.
In both the monomers of PHBV, the chiral center or the chiral carbon has four different substituents. In 3-hydroxybutanoic acid, the third carbon has these four different groups: −OH - OH, −CH3 - C{H_3}, −H - H, −CH2−COOH - C{H_2} - COOH. In 3-hydroxypentanoic acid, the third carbon has these four different groups: −OH - OH, −CH2−CH3 - C{H_2} - C{H_3}, −CH2−COOH - C{H_2} - COOH, −H - H. Hence, both these monomers are chiral.

Therefore, the correct answer is option A that is PHBV.

Note: A chiral molecule is non-superimposable on its mirror image, so that the mirror image is actually a different molecule. The two non-identical mirror images are known as the pair of enantiomers.