Question

Draw three structural isomers of butene and name them.

Answer 1

Hint: Butene is a chemical compound with molecular formula ${C_4}{H_8}$. It is an alkene and is capable of showing positional isomerism.

Complete step by step answer:
Butene, also known as butylene, is a series of alkenes with the general formula ${C_4}{H_8}$. It is a colourless gas that is present in crude oil in small amounts which are too small for viable extraction. Butene is obtained by catalytic cracking of long-chain hydrocarbons left during refining of crude oil. Cracking produces a mixture of products, and the butene is extracted from this by fractional distillation.
There are two structural isomers of butene. We can change the position of the double bond in butene to get its two isomers. The isomers are thus positional isomers in respect to each other.
When the double bond is placed between the first carbon and the second carbon, we get the first isomer of butene. The structure of this isomer is:

As the double bond is between C1 and C2, this compound is called 1 – butene.

Now, if we change the position of the double bond and place it between the second and the third carbon, we get another isomer of butene. The structure of this isomer is:

In this isomer, the double bond is between the second and the third carbon. Thus, this compound is called 2 – butene.

Now, if we change the parent chain and take one methyl group outside the parent chain, we get another isomer of butene. The structure of this isomer is:

The name of this isomer is 2 – methylpropene.

Note: One can miss the last isomer if he doesn’t change the position of the methyl group. This is one of the most common mistakes done in this question. It should also be noted that the same compound with different structural formulas has different melting and boiling points. It results in the change of physical properties.