Question

The reaction of Ph\(_3\)PCl\(_2\) with PhNH\(_2\) primarily produces

• A. Ph\(_3\)P=NPh
• B. PhP=NPh
• C. PhCl\(_2\)P=NPh
• D. Ph\(_2\)ClP=NPh

Hint:

Triphenylphosphine dichloride reacts with amines to give phosphinimines by elimination of HCl. Remember that the strong nucleophilicity of amines allows them to attack electrophilic phosphorus centers effectively. Phosphinimines are an important class of organophosphorus compounds with P=N double bonds.

Answer 1

The Correct Option is A

Step 1: The compound given is Ph\(_3\)PCl\(_2\), which is triphenylphosphine dichloride. It has the structure where phosphorus is bonded to three phenyl groups and two chlorides.
Step 2: When Ph\(_3\)PCl\(_2\) reacts with a primary aromatic amine (PhNH\(_2\)), nucleophilic substitution takes place. The amine nitrogen attacks the phosphorus center, leading to displacement of chloride ions.
Step 3: After elimination of two molecules of HCl, a double bond between P and N is formed, yielding a phosphinimine derivative.
\[ \text{Ph}_3\text{PCl}_2 + \text{PhNH}_2 \;\;\longrightarrow\;\; \text{Ph}_3\text{P}=\text{NPh} + 2\text{HCl} \] Step 4: Thus, the primary product of this reaction is \(\text{Ph}_3\text{P}=\text{NPh}\), which corresponds to option (A).