The following structural isomers are possible for C4H8with one double bond:
(I) [\ce{H2^1C = ^2CH - ^3CH2 - ^4CH3}]
(II) [\ce{^1CH3 - ^2CH = ^3CH - ^4CH3}]
(III)[\begin{array}{cc}
\ce{^1CH2 = ^2C - ^3CH3}\
\phantom{..}|\
\phantom{....}\ce{CH3}\end{array}]
The IUPAC name of
Compound (I) is But-1-ene,
Compound (II) is But-2-ene, and
Compound (III) is 2-Methylprop-1-ene