Question

The structures of four hydrocarbons are shown below:

\[\begin{array}{cc} \phantom{.....}\ce{CH3}\\ \phantom{...}|\\ \ce{H3C - C - H}\\ \phantom{...}|\\ \phantom{.....}\ce{CH3} \end{array}\]

\[\begin{array}{cc} \ce{CH3}\phantom{.....}\\ |\phantom{.......}\\ \ce{C = CH2}\\ |\phantom{.......}\\ \ce{CH3}\phantom{....} \end{array}\]

\[\begin{array}{cc} \ce{H}\phantom{.....}\\ |\phantom{.....}\\ \ce{H3C - C - C = CH2}\\ |\phantom{....}|\\ \ce{H\phantom{...}H} \end{array}\]

\[\begin{array}{cc} \phantom{...}\ce{CH3}\\ |\\ \ce{H3C - C = CH2} \end{array}\]

How many isomers of butene are there?

Options

• 1

• 2

• 3

• 4

Answer 1

4

Explanation:

Butene has the molecular formula C₄H₈. It shows chain isomerism (straight chain vs. branched chain) giving but-1-ene, but-2-ene, and 2-methylpropene. Furthermore, but-2-ene shows geometrical isomerism and exists as cis and trans forms. Therefore, the total isomers of butene are 4.