Question

In the given compound the lowest set of locants are:

(A) 3, 3, 4, 5
(B) 3, 4, 5, 5
(C) 4, 5, 3, 3
(D) None of these

Answer 1

Firstly, we should know what a locant is in order to solve this question and always the longest chain should be selected. As we know we should assign the possible lowest number to the carbon that has substituent.

Complete step by step answer:
Locant is the number of carbon on which the substituent is located. In this question we need the lowest locant set that is the sum of the number of carbon atoms on which the substituent are located should be low.
-we should select the longest chain.
This is the longest:

The other possible chains are mentioned in the below mentioned diagram which is the longest chain.

Thus, these are not the longest chain.

- We should assign the possible lowest number to the carbon that has substituent.
Will try number of trails and compare to arrive at correct answer:
Trail 1

Trail 2

- Write the locant of the structure trail 1 and trail
Trail 1: 3, 3, 4, 5
Trail 2: 3, 4, 5, 5
- Sum up all the locations obtained in trail 1 and 2:
Trail 1: 3, 3, 4, 5
= 3 + 3 + 4 + 5
=15
Trail 2: 3, 4, 5, 5
= 3 + 4 + 5 + 5
= 17

We need the least set of locants thus, option A is the correct option.

Note: Option C is 4, 5, 3, 3. Firstly obtaining this order of locants is impossible because in any chain number 3 will come first , then comes 4. But here the order itself is wrong. Thus, this option can be rejected in the place itself.