Question

How many alkyl halides are obtained from monochlorination of the alkanes shown below when stereoisomers are included?

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Answer 1

cl or 11-chloro-2-methyl pentane) (2-methylpentane) al (2-chloro- (3-chloro-2-methyl (2-1 . o 4-methyl (1-chloro. pentane) pentane) 4-methylpentane) (2-methylpentane) has i, 2 and 3-carbons and they react with e as shown above. ) h shexane cyclohexane chlorocyclohexane (chloromethyl) cyclohexane (1-chloro- i 4-methys 4-methy cyclohexane 2 3 (1-chloro-1 (1-chloro- a d methylcyclohexane) 2-methy (1-chloro- cyclohexane) 3-methys cyclohexane) CH

tol (2-chloroethyl) yclohexane + Tatu el (1-chloroethyl) (1-chloro (1-chloro- cyclohexane Tethylcyclohexane) 2-ethyl cyclohexone) (1-chloro-y-ethys cyclohexane) (1-chloro-3-ethyl cyclohexane) 0 9 xx tch ho Xx + x x (1-chloro. 22,4,4 tetramethyl pentane) (3-chloro-2,2,4,4-telfra. methylpentane)
if stereo isomers are included, then count the number of chiral carbons present in the each product molecule.

If the molecule has "n" chiral carbons, then the number of stereo isomers are 2^n.

ex: If the molecule has one chiral carbon, then the molecule will have two stereo isomers they are one R form and one S form.

c. 2-methylpentane on chlorination, form 1-chloro-2-methylpentane which does not have chiral centres so it does not have stereo isomers.

3-chloro-2-methylpentane has one chiral carbon ,so it has two stereo isomers R and S.

2-chloro-4-methylpentane has one chiral carbon , so it has two stereo isomers.

1-chloro-4-methylpentane is achiral.

So total there will be six stereo isomers.

d. chlorocyclohexane has one chiral carbon, so it has two stereo isomers.

e.

methylcyclohexane on chlorination forms chloromethylcyclohexane which is achiral.

1-chloro-1-methylcyclohexane is achiral.

1-chloro-2-methylcyclohexane has a chiral carbon ,so it has two stereoisomers.

1-chloro-3-methylcyclohexane has a chiral carbon, so it has two stereoisomers.

1-chloro-4-methylcyclohexane has a chiral carbon ,so it has two stereoisomers.

Total the given compound has eight stereo isomers.

f.

Ethylcyclohexane on chlorination, form (2-chloroethyl)cyclohexane which is achiral.

(1-chloroethyl)cyclohexane has a chiral carbon, so it has two stereoisomers.

1-chloro-1-ethylcyclohexane is achiral.

1-chloro-2-ethylcyclohexane has two chiral carbons, so it has four stereoisomers.

1-chloro-3-ethylcyclohexane has two chiral carbons, so it has four stereoisomers.

1-chloro-4-ethylcyclohexane has two chiral carbons, so it has four stereoisomers.

Total, 16 sixteen isomers are possible.

g.

2,2,4,4-tetramethylpentane on chlorination form 1-chloro-2,2,4,4-tetramethylpentane which is achiral.

3-chloro-2,2,4,4-tetramethylpentane is also achiral.

So total two isomers are possible.