Nitrogen can be estimated by Kjeldahl's method for which of the following compound?

The Kjeldahl method fails and gives inaccurate results for the following types of compounds:

1. Nitrogen present in aromatic rings

Examples:

$$\mathrm{Pyridine,\ Quinoline}$$

2. Nitrogen directly bonded to oxygen

Examples:

$$\mathrm{Nitro\ compounds}$$

3. Nitrogen-nitrogen bonded compounds

Examples:

$$\mathrm{Azo\ compounds}$$

However, benzamide can be estimated by the Kjeldahl method because the nitrogen present in the amide group is converted into ammonia during digestion.

$$\mathrm{C_6H_5CONH_2}$$

Therefore, benzamide gives a positive Kjeldahl test. Thus, the correct option is B.