Write the IUPAC name of the compound `CH_3 - CH_2 - CH_2 - COOH`

Explanation

(a) There are 4 C atoms in the chain involving-COOH group, therefore, the root word is .but..
(b) Only C-C bonds appear between C atoms in the chain, therefore, primary suffix is .ane.. Thus,
Base name = root word + primary suffix = but + ane = butane
(c) There is --COOH group in the chain, therefore, secondary suffix is .oic acid..
Thus, the IUPAC name of the given compound is derived as:
Butane named -e + Secondary suffix
Butane - e + oic acid = Butanoic acid