CH3CH2CONH2 is an amide. To understand why, let’s break down the structure and definitions of these functional groups.
Amides are organic compounds that are derived from carboxylic acids, where the hydroxyl group (-OH) is replaced by an amine group (-NH2). In the case of CH3CH2CONH2, we can see that it has a carbonyl group (C=O) adjacent to a nitrogen atom that is also bonded to two hydrogens (NH2). This structure aligns perfectly with that of an amide.
On the other hand, carboxylic acids have a -COOH group, which is not present in this compound, and esters are characterized by a -COOR group, where R is a hydrocarbon chain. Since CH3CH2CONH2 does not fit either of these definitions, it cannot be classified as a carboxylic acid or an ester.
In conclusion, due to its structure containing the carbonyl adjacent to the nitrogen, CH3CH2CONH2 is classified as an amide.