Chapter 21, Problem 69A

Interpretation Introduction

Interpretation:

The pair of structural isomers needs to be identified from the given condensed structural formulas.

Concept introduction:

The molecules having same molecular formula but differ in structural arrangement of atoms are said to be isomers of each other.

Answer to Problem 69A

The pair of structural isomers in the given compound are:

• a and b.
• a and c.
• a and d.
• c and d.
• c and b.

Explanation of Solution

Given:

1. The parent (longest) continuous carbon chain is identified.

2. The ending of the parent chain for alkane (-e) is -ane.

3. Name should be written in alphabetical order and numbering should be done in such a way that the substituent group gets lowest number.

4. Hyphen is used to connect the number to the name.

For number of carbons atoms in alkane chain, the prefix is given as:

Carbon-1   meth

Carbon-2   eth

Carbon-3   prop    

Carbon-4   but      

Carbon-5   pent

Carbon-6   hex

Carbon-7   hept

Carbon-8   oct

Carbon-9   non     

Carbon-10       dec

The numbering is done in such a way that the substituents gets lower number and the compound has longest carbon chain as a parent chain as:

The molecular formula of all the compounds is same that is, and the name of compounds a and c are different and of compound b and d are same, compound b and d are same but are isomers to a and c and a and c are isomers to each other also.

Hence, the pair of structural isomers in the given compound are:

• a and b.
• a and c.
• a and d.
• c and d.
• c and b.