Explanation:
1) 3-ethyl hex-1-yne
2) 3-methyl hex-1-yne
3) 4-ethyl hept-2-yne
4) 4,5-dimethyl hept-2-yne
5) 3,5-diethyl non-1-yne
6) 5-ethyl-4,6,7-trimethyl non-2-yne
