Question

Give the structural formula and IUPAC names of the following compounds
(a) Malonic acid
(b) Succinic acid.

Answer 1

Hint:Malonic acid and succinic acid are dicarboxylic acids belonging to a homologous group, that is, compounds which differ only by a $ - C{H_2}$ group and molecular mass of $14$. Malonic acid is the second member of this series while succinic acid is the third member.

Complete step by step answer:
Both malonic acid and succinic acid belong to dicarboxylic acids, meaning that they have two carboxylic acid ($ - COOH$) groups in their structure. They are also members of a homologous series, which are compounds which differ only by a $ - C{H_2}$ group and molecular mass of $14$. The first member of this series is oxalic acid, which has only two $ - COOH$ groups. Malonic acid being the next member, has a $ - C{H_2}$ group in between the two carboxylic acid groups, while succinic acid, the next member, has two $ - C{H_2}$ groups. With this information, we can draw their structure as follows:

For the IUPAC name of malonic acid, let us start counting the carbon atoms from the left. We have 3 carbon atoms and two carboxylic acid groups on the first and third carbon atoms. For the three carbon atoms, we have to include “propane” and to account for the two carboxylic acids, we include “dioic acid” with the numbers at which they are present written at the beginning. Hence the IUPAC name is:
$1,3$ – propanedioic acid
For the IUPAC name of succinic acid, let us start counting the carbon atoms from the left. We have 4 carbon atoms and two carboxylic acid groups on the first and fourth carbon atoms. For the four carbon atoms, we have to include “butane” and to account for the two carboxylic acids, we include “dioic acid” with the numbers at which they are present written at the beginning. Hence the IUPAC name is:
$1,4$ – butanedioic acid

Note:
While writing IUPAC name, numbering of carbon atoms should begin from the closest carbon atom to the functional group. Here as both the compounds are symmetric (same groups of atoms on either side of a line drawn through the middle of the compound) and contain the same functional group, we can start numbering from any side and still get the same answer. When two or more functional groups are present, numbering should be done according to the series of preference of functional groups.