COMEDK2023Evening ShiftChemistryHaloalkanes and HaloarenesActual
The reactions taking place with 2- Phenyl-2-bromopropane as the starting material is shown below. Identify [A] and [B] formed in the reaction. C ₆ H ₅- C ( CH ₃ )₂⁻ Br [ ] KOH Alcoholic [ A ] [ A ]+ HBr ( C ₆ H ₅ CO )₂ O . [ B ]
Options
- A[ A ]=2 - Phenylpropan-2-ol [ B ]=2 -Phenyl-2-bromopropene
- B[A]=4 -Hydroxyphenyl-2-bromopropane [B]=4 -Hydroxyphenylpropene
- C[ A ]=2 -Phenylpropene [ B ]=2 -Phenyl-1- bromopropane
- D[ A ]=2 -Bromopropene [ B ]=1 -Bromopropane
Correct answer
C. [ A ]=2 -Phenylpropene [ B ]=2 -Phenyl-1- bromopropane
Step-by-step solution
The starting material is 2-phenyl-2-bromopropane, which is a tertiary alkyl halide. Treatment with alcoholic KOH under heating conditions leads to a dehydrohalogenation reaction via the E2 mechanism. The elimination of HBr from 2-phenyl-2-bromopropane results in the formation of 2-phenylpropene as the major product [A]. The reaction is: C₆H₅-C(CH₃)₂Br KOH, C₆H₅-C(CH₃)=CH₂ + KBr + H₂O . The second step involves the reaction of 2-phenylpropene [A] with HBr in the presence of benzoyl peroxide, (C₆H₅CO)₂O₂ . This is a