Question

Kjeldahl's method cannot be used for the estimation of nitrogen in which compound?
 

(A)	(B)	(C)	(D)
NH2-CH2-COOH	C6H5-NH2	C6H5-N=N-C6H5	O2N-C6H4-NO2

• A. A
• B. B
• C. C
• D. D

Hint:

Key Points:
Kjeldahl's method requires nitrogen to be convertible to ammonium sulfate Works only for nitrogen in $\mathrm{-3$ oxidation state Fails for $\mathrm{N=N$, $\mathrm{NO_2$, $\mathrm{CN$ groups Azobenzene (C) contains stable N=N bonds resistant to digestion

Answer 1

The Correct Option is C

Kjeldahl's method is suitable for estimating nitrogen in:

• Amino acids (A)
• Amines (B)
• Amides
• Other compounds where nitrogen is in -3 oxidation state

It cannot be used for:

• Azo compounds (C) -N=N-
• Nitro compounds (D, H) -NO₂
• Nitriles (E) -CN
• Diazonium salts