Question

$C{H}_3-\stackrel{C{H}_3}{\stackrel{|}{\underset{C_2{H}_5}{\underset{|}{C}}}}-\underset{OH}{\underset{|}{CH}}-C{H}_3$

Write the $IUPAC$ name of the above compound :

• A. $3-hydroxy-3,3-dimethyl-pentane$
• B. $2-hydroxy-3,4-dimethyl-pentane$
• C. $2-hydroxy-3,7-dimethyl-pentane$
• D. $2-hydroxy-3,3-dimethyl-pentane$

Answer 1

The correct option is D $2-hydroxy-3,3-dimethyl-pentane$

Rules for Naming Hydrocarbons:-

Rule-I Selection of the longest carbon chain.

Rule-II Numbering the longest chain: Longest chain is numbered starting from a terminal carbon. Numbering is done is such a way that lowest possible number is given to the side chain or a functional group.

Rule-III Writing names of branched, saturated hydrocarbons, locants are written first in alphabetical order followed by name of parent chain.

Rule-IV Some common names are retained in $IUPAC$ system for unsubstituted hydrocarbon only.

(Refer to Image 1)

As $-OH$ should be given preference so,

numbering will start from right hand side to give less numbering to $C$ of $-OH$.

(Refer to Image 2)

Longest chain is $5$ membered.

So, naming is $2-hydroxy-3,3-dimethyl-pentane$.