Chapter 21, Problem 53A

How does the structure of a cycloalkane differ from that of a straight-chain or branched-chain alkane?

Interpretation Introduction

Interpretation:

The difference in structure of cycloalkane from that of a straight chain or branched-chain alkane needs to be explained.

Concept introduction:

When the carbon atoms of hydrocarbons are arranged in such a way that it results in the formation of ring then it is said to be cycloalkanes.

Answer to Problem 53A

The difference in structure of cycloalkane from that of a straight chain or branched-chain alkane is that cycloalkanes contains 2 H atoms less than that of straight chain or branched-chain alkane.

Explanation of Solution

The general formula of alkane is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2}}$. So, for an alkane having 5 carbon atoms is a linear chain, the formula of the alkane will be ${\text{C}}_5{\text{H}}_{\text{12}}$, pentane that means pentane contains 5 carbon atoms and 12 hydrogen atoms as shown:

The branched chain of 5 carbon atoms will be:

For a cycloalkane formed from 5 carbon atoms, the structure and the molecular formula will be:

Cyclopentane that means it contains 5 carbon atoms and 10 hydrogen atoms.

Since, in cycloalkane the number of hydrogen atoms are less from alkane by 2 units so, the general formula of cycloalkane will be:

${\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2-2}}{\text{ = C}}_{\text{n}}{\text{H}}_{\text{2n}}$

Hence, the difference in structure of cycloalkane from that of a straight chain or branched-chain alkane is that cycloalkanes contains 2 H atoms less than that of straight chain or branched-chain alkane.