Question

The common name of $C{{H}_{3}}C{{H}_{2}}COOH$ :
(A) propionic acid
(B) Butyric acid
(C) Vinegar
(D) Methanoic acid

Answer 1

Carbon compounds containing a carboxyl functional group, -COOH are carboxylic acids. This carboxyl group consists of –C=O and O-H group, which are named carbonyl group and hydroxyl group respectively. So this –COOH group is called the carboxyl group. The common name for this functional group is –ic acid as a suffix.

Complete step by step solution:
In the IUPAC system, the functional group present in the molecule is identified which determines the choice of appropriate suffix.
The longest chain of carbon atoms containing the functional group is numbered in such a way that the functional group is attached to the carbon atom possessing the lowest possible number in the chain.
According to IUPAC nomenclature, aliphatic carboxylic acids are named by replacing the ending ‘-e’ in the name of the corresponding alkane with – oic acid.
In numbering the carbon chain starts from carboxylic group carbon is numbered one. If the alkyl chain has more than one carboxylic group indicated by adding the multiplicative prefix as di-, tri-, etc.
The given molecule, $C{{H}_{3}}C{{H}_{2}}COOH$
The number of carbons in the molecule is 3. If the number of carbon is 3, it will be named as propane with a single bond and carboxylic acid group –oic acid.

The common name of the given molecule is propionic acid.

Note: Carboxylic acids amongst the earliest organic compounds, isolated from nature and a large number of compounds known by the common names. For example, formic acid $HCOOH$, acetic acid $C{{H}_{3}}COOH$ is known as vinegar, butyric acid $C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}COOH$.