Question

For which of the following. Kjeldahl's method is not used for the estimation of nitrogen?
I. Aniline
II. Azobenzene
III. Nitrobenzene
IV. Pyridine

• A. II, III, IV
• B. II , III only
• C. III, IV only
• D. I, III, IV

Answer 1

Answer: (A)

(a) Key Idea The groups in which nitrogen contain double bond or present in heterocyclic ring can not be estimated by Kjeldahl's method.

(I) Structure of aniline is



as nitrogen in aniline does not contain double bond, it can be estimated by Kjeldahl’s method.

(II) Azobenzene contain $-N=N-$ group, thus does not estimated by Kjeldahl's method.

(III) In nitrobenzene, nitrogen also contains



double bond, thus can not be estimated by Kjeldahl's method.

(IV) Pyridine is a heterocyclic organic compound in which nitrogen is present in cyclic ring.



Thus, it is also not estimated by Kjeldahl’s method.