Question

A student incorrectly names an organic hydrocarbon 4-butyl-2,3-dimethylpentane. What is the correct name for this substance? 1. 2,3,4-trimethyloctane 2. 2,3-dimethylnonane 3. 1,1,2,2-tetramethylpentane 4. 2-isopropyl-3-methylheptene 5. 5,6-dimethyl-6-isopropylhexane 6. 5,6-dimethylpentane

Answer 1

Butyl group is CH3 CH2 Ch2 CH2 -

Methyl group is CH3 -

Pentane is CH3 CH2 CH2 CH2 CH3

4 - butyl - 2,3 dimethylpentane is


         CH3    CH2 CH2 CH2 CH3
         |           |
CH3 CH CH CH CH3
               |
              CH3

You can realize that there is a chain of 8 Cs (I bolded it).

The proper name must use the longest C chain; i.e octane.


In this case, there are 3 methyl groups attached to the 8 Cs chain, and they are at 2, 3 and 4 positions. Therefore, the name is:


2, 3, 4 trimethyl - octane