Question

The IUPAC name of the isobutyl chloride is:
A.${\text{2 - methyl - 2 - chlorobutane}}$
B.${\text{2 - chloro - 2 - methylbutane}}$
C.${\text{1 - chloro - 2 - methylpropane}}$
D.${\text{2 - methyl - 3 - chloropropane}}$

Answer 1

Hint: The term iso- stands for isomer and is usually used when there is one methyl group located on the second carbon of a carbon chain. And the term neo pentane means that four Carbon atoms are attached to one atom.

Complete step by step solution:
First of all we will talk about the alkanes, alkenes and alkynes.
Alkanes: The compounds which are formed by carbon and hydrogen and have only a single bond between the carbon-carbon atoms, are known as alkanes. For example: The first member of the alkane family is ethane $({H_3}C - C{H_3})$. The general formula of the alkane group is ${C_n}{H_{(2n + 2)}}$.
Alkenes: The compounds which are formed by carbon and hydrogen and have at least one double bond along with a single bond between the carbon-carbon atoms, are known as alkenes. For example: The first member of the alkene family is ethene $({H_2}C = C{H_2})$. The general formula of the alkene group is ${C_n}{H_{2n}}$.
Alkynes: The compounds which are formed by carbon and hydrogen and have at least one triple bond along with a single bond between the carbon-carbon atoms, are known as alkynes. For example: The first member of the alkyne family is ethyne $(HC \equiv CH)$. The general formula of the alkyne group is ${C_n}{H_{(2n - 2)}}$.

Number of carbon atom in alkane	Name of the parent chain
One	Methane
Two	Ethane
Three	Propane
Four	Butane
Five	Pentane
Six	Hexane
Seven	Heptane

The term iso- stands for isomer and is usually used when there is one methyl group located on the second carbon of a carbon chain. And the term neo pentane means that four Carbon atoms are attached to one atom.
The first step in the IUPAC naming system is to identify the longest carbon chain i.e. here in the case of isobutyl chloride is three carbon chains i.e. propane.
Branching is present at the second carbon of the parent chain. So number the carbon atoms from the side where chlorine atom is present if chlorine is at left then numbering will be from left to right otherwise from right to left. For the second carbon atom there is one methyl group attached. So the IUPAC name will be ${\text{1 - chloro - 2 - methylpropane}}$.

Hence, option C is correct.

Note:
Functional group: In hydrogen the atoms or groups which are other than carbon and hydrogen, are known as function groups. For example: chloride if chlorine is present in the compound. And if hydroxide group i.e. $OH$ is present then the name will be alcohol.