A compound (A) when reacted with PCl5 and then with NH3 gave (B), (B) ...
°C gave a compound (D) which on heating with Cu gave benzene. Deduce the structure of the compound (A).
The reaction sequence can be summarized as follows:
A + PCl5 → B
B + Br2 + KOH → C
C + NaNO2 + HCl → D
D + Cu → benzene
First, we need to determine the structures of B, C, and D in order to work backwards and deduce the structure of A.
B is the product of the reaction between A and PCl5 followed by NH3. This is a classic reaction for converting alcohols to alkyl chlorides via an SN2 mechanism. Therefore, B is likely an alkyl chloride. The exact structure depends on the structure of A and the specific conditions of the reaction.
C is the product of the reaction between B, Br2, and KOH. This reaction is known as the Hell-Volhard-Zelinsky reaction and is used to convert carboxylic acids to α-bromo acids. Therefore, C likely contains a carboxylic acid group. The α-bromo acid product would then be deprotonated by the KOH to form the corresponding α-bromo carboxylate.
D is the product of the reaction between C, NaNO2, and HCl at 0°C. This is the Sandmeyer reaction, which is commonly used to convert primary aromatic amines to aryl diazonium salts. Therefore, D is likely an aryl diazonium salt.
Finally, the fact that D can be heated with Cu to produce benzene indicates that D contains a phenyl group. When aryl diazonium salts are heated with Cu, they undergo a coupling reaction to form an aryl-aryl bond, which in this case would be a bond between two phenyl groups to form benzene.
Putting all of this together, we can deduce that A is likely a compound containing a phenyl group and a carboxylic acid group. One possible structure for A is benzoic acid (C6H5COOH), which would give the following reaction sequence:
benzoic acid + PCl5 → benzoyl chloride
benzoyl chloride + NH3 → benzamide
benzamide + Br2 + KOH → 2-bromobenzoic acid
2-bromobenzoic acid + NaNO2 + HCl → 2-bromo-1-nitrobenzene
2-bromo-1-nitrobenzene + Cu → benzene
A compound (A) when reacted with PCl5 and then with NH3 gave (B), (B) ...
Catch the question from the stage where C is being produced.
Br2+KOH combination is used in only Hoffmann bromamide reaction. In this reaction the reactant is an amide. That means B amide hai.
Chalo ab dekhte hain ki yeh amide kaise bana.
Here NH3 is used which is used to make amide from a carboxylic acid. That means ki A is a carboxylic acid.
That means ki answer is A or D.
Final product o-cresol hai. o-Cresol me ortho position par CH3 group hota hai. Is group par reaction ka koi asar nahi hoga. That means ki A is the correct answer bcoz it has both the groups i.e. COOH and CH3 at ortho position.
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