Question

In a carbon compound, the side chains are present at 2,7,9 or 3,4,9 positions. Which positions should be considered for nomenclature?

• A. 3,4,9
• B. 2,7,9
• C. Both can be considered equally
• D. Data insufficient

Answer 1

Answer: (B)

2,7,9

When series of locants containing the same number of terms are compared term by term, that series which contains the lowest number on the occasion of the first difference is preferred. In the given molecule, the numbering can be done from either side of the chain. However, the 2,7,9 is chosen since, it has lowest number i.e., 2 on the first occasion of difference when compared with the other set: 3,4,9.