Question

Major product obtained during the following reaction sequence is:

• A. 2,2'-diaminobiphenyl
• B. 2,3'-diaminobiphenyl
• C. A saturated cyclic diamine
• D. A derivative of naphthalene with two amino groups

Answer 1

Answer: (A)

2,2'-diaminobiphenyl

Answer 2

The reaction sequence begins with phenanthrene.

Step 1: Ozonolysis with oxidative workup (O3/H2O2) Phenanthrene undergoes ozonolysis at the 9,10 double bond. With oxidative workup (H2O2), this cleavage results in the formation of two carboxylic acid groups, yielding diphenic acid (2,2'-biphenyldicarboxylic acid).

The structure of diphenic acid is:

      COOH
      |
      C1----C2
     / \   / \
    C6  C   C3
   /     \ /     \
  C5------C4------C1'
   \     / \     /
    C---C---C---C
     \ /     \ /
      COOH

Step 2: Reaction with hydrazoic acid and sulfuric acid (N3H/H2SO4) - Schmidt Reaction Diphenic acid, having two carboxylic acid groups, reacts with hydrazoic acid in the presence of sulfuric acid. This is the Schmidt reaction, where a carboxylic acid is converted into a primary amine with the loss of CO2.

Applying this to diphenic acid: Each -COOH group is converted to an -NH2 group.

The resulting product is 2,2'-diaminobiphenyl.

The structure of 2,2'-diaminobiphenyl is:

      NH2
      |
      C1----C2
     / \   / \
    C6  C   C3
   /     \ /     \
  C5------C4------C1'
   \     / \     /
    C---C---C---C
     \ /     \ /
      NH2

This structure corresponds to option (A).