How many alkynes with the molecular formula `C_5H_8` are possible?

Options

A. 5
B. 4
C. 2
D. 3

Answer

D

Explanation

for 5 C's, three skeletons are possible.
`C-C-C-C-C" "C-underset(C)underset(|)(C)-C-C" "C-underset(C)underset(|)overset(C)overset(|)(C)-C`
Since a C atom cannot form more than 4 bonds, `C-=C` is not possible with the tertiary and quaternary carbons. Thus, different possibilities are
`C-=C-C-C-C,C-C--=C-C-C,C-underset(C)underset(|)(C)-C-=C`