Question

Among the isomeric alkanes of molecular formula C5H12, identify the one that on photochemical chlorination yields.
(1) A single monochloride
(2)three isomeric monochloride
(3)four isomeric monochloride

Answer 1

i) To have a single monochloride, there should be only one type of H-atom in the isomer of the alkane of the molecular formula C5H12. This is because, replacement of any H-atom leads to the formation of the same product. The isomer is neopentane.

Neopentane

(ii) To have three isomeric monochlorides, the isomer of the alkane of the molecular formula C5H12 should contain three different types of H-atoms.

Therefore, the isomer is n-pentane. It can be observed that there are three types of H atoms labelled as a, b and c in n-pentane.

(iii) To have four isomeric monochlorides, the isomer of th

e alkane of the molecular formula C5H12 should contain four different types of H-atoms. Therefore, the isomer is 2-methylbutane. It can be observed that there are four types of H-atoms labelled as a, b, c, and d in 2-methylbutane.

Answer 2

To have a single mono-chloride , there should be only one type of H−atom. This is because, replacement of any H−atom leads to the formation of same product.

∴ The isomer C

5

H

12

that leads to a single mono-chloride is neo-pentane.

CH

3

−

CH

3

∣

C

∣

CH

3

−CH

3

ii) To have 3 isomeric mono-chlorides, the isomer should contain 3 different types of H−atoms.

∴ The isomer should be n−pentane.

CH

3

c

−

CH

2

b

−

CH

2

a

−

CH

2

b

−

CH

3

c

iii) To have 4 isomeric mono-chlorides, the isomer should contain 4 different types of H−atoms.

∴ The isomer is 2−methylbutane.