JEE Main Chemistry: Organic Chemistry - Nitrogen Compounds questions with solutions

Q1. Which of the following is an incorrect statement regarding the Griess-I test for nitrite ions?

1. The diazotised acid couples with 1-Naphthylamine to form a red azo dye.
2. Acidification with acetic acid ensures formation of HNO2 which then causes diazotisation of sulphanilic acid.
3. The red azo dye forms regardless of the concentration of the test solution.
4. The red azo dye molecule contains three nitrogen atoms in a single molecule.

Answer: The red azo dye forms regardless of the concentration of the test solution.

In the Griess-I test: sulphanilic acid is diazotised by HNO2 (formed from nitrite under acidic conditions), and the diazonium salt couples with 1-naphthylamine to give a red azo dye. Statements A, B, and D are correct. Statement C is incorrect because the test has a sensitivity limit; very dilute nitrite solutions do not produce detectable azo dye colour.

Q2. Which of the following compounds reacts with HNO2 (nitrous acid) to produce a carboxylic acid?

1. C6H5COCl
2. C6H5CONH2
3. CH3COOCOCH3
4. CH3COOC2H5

Answer: C6H5CONH2

Primary amides react with nitrous acid (HNO2) through a diazotization-like mechanism: the NH2 of the amide is converted to a diazonium-like intermediate that decomposes releasing N2, yielding the parent carboxylic acid. Acid chlorides, anhydrides, and esters do not react with HNO2 to give carboxylic acids under normal conditions.