Question

The IUPAC name of $NC - C{H_2} - C{H_2} - COOH$ is:
A. 3-carboxy propanenitrile
B. 4-cyano butanoic acid
C. 2-cyano methane carboxylic acid
D. 3-cyanopropanoic acid

Answer 1

Hint: For naming an organic compound, one should remember the rules of IUPAC nomenclature and the priority order in naming the organic compounds. The priority order of carboxylic acid is greater than that of cyano or carbonitrile groups.

Complete step by step answer:
In order to do the nomenclature of the given compound, first we have to redraw the compound.
$NC - C{H_2} - C{H_2} - COOH$
We will proceed further with the nomenclature in a series of steps.
(i) First of all, we try to find the longest parent chain such that we can mark the root word of the name of the organic compound. In this case, the parent chain has 3 carbon atoms as the longest chain and thus, the root word is prop.
(ii) Next, we explain why we don’t add the carbon atom of cyanide group in the parent chain. Thus is because when we give priority to the carboxylic acid as the main functional group, we consider the cyanide group as the substituent.
(iii) In the next step, we look for any degree of unsaturation within the parent chain and search for the presence of any multiple bond. In this case, no double or triple bond is present in the parent chain.
(iv) Next, we find the suitable prefixes and suffixes for the compound. In this case, the prefix is cyano- and the suffix is –oic acid.
(v) Now, place the numbering in such a way that the functional group gets the lowest numbering.
In the end, we find the name of the given organic compound to be 3-cyanopropanoic acid.
Thus, the correct option is (D) 3-cyanopropanoic acid.

Note:
In the priority list of naming the functional groups in organic compounds, carboxylic acid has a higher priority than the cyanide group. Thus, it is necessary to remember the priority of the functional groups and the substituent while doing the nomenclature of an organic compound.