Write the types of isomers for $C_4H_6$ (alkyne) and provide one example for each.

(N/A) The molecular formula $C_4H_6$ corresponds to an alkyne (general formula $C_nH_{2n-2}$).
$(a)$ Position Isomers:
$CH_3-CH_2-C \equiv CH$ (But$-1-$yne)
$CH_3-C \equiv C-CH_3$ (But$-2-$yne)
$(b)$ Chain Isomers:
There are no chain isomers for $C_4H_6$ alkynes as the carbon chain cannot be branched without violating valency.
$(c)$ Functional Isomers (Dienes):
$CH_2=C=CH-CH_3$ (Buta$-1,2-$diene)
$CH_2=CH-CH=CH_2$ (Buta$-1,3-$diene)
$(d)$ Cyclic Isomers:
$1$-Methylcyclopropene,$3$-Methylcyclopropene,and Cyclobutene.