Question 15.1: Assign IUPAC names to the following aldehydes. a....
Assign IUPAC names to the following aldehydes.
a. \begin{matrix} \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad O \\ CH_{3}-CH_{2}-CH_{2}-CH_{2}-\overset{||}{C}-H \end{matrix} b. 
c. \begin{matrix} \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad O \\ CH_{3}-CH_{2}-CH_{2}-\underset{|}{C} H-\overset{||}{C}-H \\ \quad\quad\quad\quad\quad\quad \underset{|}{C}H_{2} \\ \quad\quad\quad\quad\quad\quad CH_{3} \end{matrix} d. \begin{matrix} \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad O \\ CH_{3}-CH_{2}-\underset{|}{C} H-CH_{2}-\overset{||}{C}-H \\ OH \quad \end{matrix}
a. The parent chain name comes from pentane. Remove the –e ending and add the aldehyde suffix –al. The name becomes pentanal. The location of the carbonyl carbon atom need not be specified because this carbon atom is always number 1. The complete name is simply pentanal.
b. The parent chain name is butanal. To locate the methyl group, we number the carbon chain beginning with the carbonyl carbon atom. The complete name of the aldehyde is 3-methylbutanal.
c. The longest chain containing the carbonyl atom is five carbons long, giving a parent chain name of pentanal. An ethyl group is present on carbon 2. Thus the complete name is 2-ethylpentanal.
\begin{matrix} \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad O \\ \overset{5}{C} H_{3}-\overset{4}{C} H_{2}-\overset{3}{C}H_{2}-\underset{|}{\overset{2}{C}} H-\overset{1||}{C}-H \\ \quad\quad\quad\quad\quad\quad \underset{|}{C}H_{2} \\ \quad\quad\quad\quad\quad\quad CH_{3} \end{matrix}d. This is a hydroxyaldehyde, with the hydroxyl group located on carbon 3.
\begin{matrix} \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad O \\ \overset{5}{C} H_{3}-\overset{4}{C} H_{2}-\underset{|}{\overset{3}{C} } H-\overset{2}{C} H_{2}-\overset{1||}{C}-H \\ OH \quad \end{matrix}The complete name of the compound is 3-hydroxypentanal. An aldehyde functional group has priority over an alcohol functional group in IUPAC nomenclature. An alcohol group named as a substituent is a hydroxy group.