Question

The compounds that will give an isomer of 2,2-dimethylpropane on catalytic hydrogenation are
1.

2.

3.

4.

A. 1 and 4
B. 2 and 4
C. 1 and 3
D. 1 and 2

Answer 1

Hint: 2,2-dimethylpropane has five carbon atoms and is also called neopentane. It is a structural isomer of pentane. It is a double-branched-chain alkane. Structural isomers are the compounds having the same molecular formula but different structures

Complete Step by Step Solution:
Here in this question, we are given some hydrocarbons and we have to find out which one of those will give an isomer of 2,2-dimethylpropane on catalytic hydrogenation.
2,2-dimethylpropane as we know is an isomer of the alkane pentane.
So, the hydrocarbon which will have 5 carbon atoms is the isomer of 2,2-dimethylpropane.
1.

Image: Option 1
This compound on hydrogenation will give 2-methyl butane.
It has five carbon atoms.
So, it is an isomer of 2,2-dimethylpropane.
So, 1 is correct.

2.

Image: Option 2
This compound on hydrogenation will give butane.
So, it is not an isomer of 2,2-dimethylpropane.
So, 2 is incorrect.

3.


Image: Option 3
This compound on hydrogenation will give pentane.
So, it is an isomer of 2,2-dimethylpropane.
So, 3 is correct.

4.

Image: Option 4
This compound on hydrogenation will give 2,3-dimethyl butane. It is an isomer of hexane.
So, 4 is incorrect.
As both options 1 and 3 are correct. So, C is the correct option.
So, option D is correct.

Note: Stereoisomerism is a type of isomerism in which the bonds are similar but the comparative positions of the atoms are different. Enantiomers are a type of stereoisomers that are mirror images of each other that are non-superimposable. These two compounds possess similar physical properties but differ in the path in which they rotate polarised light.