Question: 60: The Kjeldahl’s method for the estimation of nitrogen can be used to estimate the amount of nitrogen in which one of the following compounds?
Answer: Option (1)
Explanation:
Kjeldahl’s method is used for the estimation of nitrogen present in organic compounds where nitrogen is present in the form of amine or amide groups.
In this method, nitrogen is converted into ammonium sulfate during digestion with concentrated sulfuric acid, and the amount of ammonia released is measured.
Kjeldahl’s method cannot be used for compounds in which nitrogen is present in nitro \mathrm{NO}_{2}, azo \mathrm{-N=N-},
or heterocyclic ring forms, because such nitrogen does not get converted into ammonium ions during digestion.
Compound (1) contains nitrogen in the form of an amine group \mathrm{-NH}_{2},
which is suitable for estimation by Kjeldahl’s method.
Compound (2) contains azo nitrogen \mathrm{-N=N-}, compound (3) contains nitro nitrogen \mathrm{NO}_{2}, and compound (4) contains ring nitrogen,
all of which are not estimated by Kjeldahl’s method.
Therefore, the correct answer is option (1).