Question

Question 12.5 Which of the following represents the correct IUPAC name for the compounds concerned?

(a) 2,2-Dimethylpentane or 2-Dimethylpentane

(b) 2,4,7-Trimethyloctane or 2,5,7-Trimethyloctane

(c) 2-Chloro-4-methylpentane or 4-Chloro-2-methylpentane

(d) But-3-yn-1-ol or But-4-ol-1-yne

Class XI Organic Chemistry : Some Basic Principles and Techniques Page 361

Answer 1

(a) 2,2-Dimethylpentane or 2-Dimethylpentane
Answer : 2,2-Dimethylpentane
reason : due to two alkyl group on the same carbon its locant is repeated two times .
hence, 2,2-dimethylpentane is the right answer .

(b) 2,4,7-Trimethyloctane or 2,5,7-Trimethyloctane
answer : 2,4,7-Trimethyloctane
reason : due to 2,4,7 locant is set of lower than 2,5,7 . 2,4,7 -Trimethylocatne is the right answer .

(c) 2-Chloro-4-methylpentane or 4-Chloro-2-methylpentane
answer : 2-Chloro-4-methylpentane
reason : due to alphabetical order of substituents, 2-chloro - 4-methylpentane is right answer.

(d) But-3-yn-1-ol or But-4-ol-1-yne
answer : But-3-yn-1-ol
reason : due to the rule of "lower locant for the principal functional group" { here alcohol is principal functional group}

Answer 2

Answer:

Explanation:

a) There are 2 methyl functional groups . So 2,2- Dimethylpentane is correct name.

b) Substituents get lowest number as far as possible. So , 2,4,7 - Trimethyloctane is correct name.

c) By considering alphabetical order , chlorine group should get lowest number. So , 2-Chloro-4-methylpentane is correct name.

d) principle functional group gets lowest number of carbon . So But-3-yn-1-ol is correct.