The correct IUPAC name of the following alkane is

1. 3,6-Diethyl-2-methyloctane

2. 5-Isopropyl-3-ethyloctane

3. 3-Ethyl-5-isopropyloctane

4. 3-Isopropyl-6-ethyloctane

 

1. HINT: Use basic rules of IUPAC nomenclature.
 
The correct IUPAC name is
Longest chain - 8C atom alkane = octane
Branch on 2, 3, 6 follows lowest sum rule.
Branch of 2 - C - methyl; 3, 6, C atom-ethyl.
Ethyl comes alphabetically before methyl.
Hence, 3,6-diethyl 2-methyl octane.