Question

The following names are all incorrect or incomplete, but they represent real structures. Draw each structure and name it correctly.

(a)$\text{2-ethylpentane}$

(b) $\text{3-isopropylhexane}$

(c) $\text{5-chloro-4-methylhexane}$

(d) $\text{2-dimethylbutane}$

(e) $\text{2-cyclohexylbutane}$

(f)$\text{2,3-diethylcyclopentane}$

Short answer

(a)

(b)

(c)

(d)

(e)

(f)

Step-by-step solution

Alkanes

Alkanes are hydrocarbon containing only single bonds. The general formula for alkane is ${\mathbf{\text{C}}}_{\mathbf{\text{n}}}{\mathbf{\text{H}}}_{\mathbf{\text{2n+2}}}$,where n = number of carbon atoms.

Rules for naming alkanes

In order for an alkane to be named, following rules must be followed.

(a) The longest continuous chain of carbon atoms is identified, which gives the base name.

(b) Starting with the end nearest a branch, the longest carbon chain is numbered.

(c) Substituents present on the longest chain, such as alkyl groups, are named, and each substituent is located by the number of the main chain carbon atoms to which it is attached.

(d) Listing is done in alphabetical order if two or more substituents are present. Prefixes like di-, tri-, tetra-, etc., are used if there are two or more of the same alkyl substituents.

Identifying the correct name and drawing its structure

(a)The correct name will be $\text{3-methylhexane}$.

(b)The correct name will be$\text{3-ethyl-2-methylhexane}$.

(c)The correct name will be$\text{2-chloro-3-methylhexane}$.

(d)The correct name will be$\text{2,2-dimethylbutane}$.

(e)The correct name will be$\text{butylcyclohexane}$.

(f)The correct name will be$\text{1,2-diethylcyclopentane}$.