Question

Which of the following compounds will be suitable for Kjeldahl's method for nitrogen estimation?

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The Correct Option is B

Kjeldahl's method is a widely used technique for the estimation of nitrogen in organic compounds. However, this method has certain limitations regarding the type of nitrogen-containing compounds it can accurately analyze. The key principle of Kjeldahl's method involves the digestion of the sample with concentrated sulfuric acid, which converts organic nitrogen into ammonium sulfate. The ammonium ions formed are then converted into ammonia and measured. 

For Kjeldahl's method to be suitable, compounds should not contain nitrogen in forms like nitro (–NO₂), azo (–N=N–), nitroso (–NO), or in rings like pyridine, as these forms are not easily converted to ammonium ions under Kjeldahl digestion conditions.

Let's analyze the given options to determine which compound is suitable for Kjeldahl's method:

1. The first compound imageis not suitable if it contains nitro or azo groups. Examining this, we see such a group; hence, it's not ideal for Kjeldahl's method.
2. The second compound imageshows nitrogen in a typical organic combination (like an amide). This form of nitrogen is suitable for conversion to ammonium sulfate during digestion and hence is suitable for Kjeldahl's method.
3. The third compound imagecontains nitrogen in a ring, which may not be completely converted to ammonium ions during digestion, making it unsuitable for this method.
4. The fourth compoundcontains other forms of nitrogen (potentially aromatic), which are also not suitable for Kjeldahl conversion.

Thus, the compound depicted in the second image

is the suitable choice for estimation using Kjeldahl's method as it allows for the nitrogen to be efficiently converted to ammonium ions.