COMEDK202510 May 2025Morning ShiftChemistryHaloalkanes and HaloarenesActual
Which one of the following is a true statement with reference to reaction between 2- Bromo-2-methylpropane and aqueous KOH ?
Options
- AThe reaction is not favoured by the presence of polar protic solvent.
- BThe reaction occurs at a slow rate since it follows S _ N 2 mechanism.
- CThe reaction occurs at a fast rate since the substrate is a tertiary alkyl halide and follows S _ N 1 mechanis
- DThe rate of reaction depends on the concentration of the haloalkane and the nucleophile OH ⁻
Correct answer
C. The reaction occurs at a fast rate since the substrate is a tertiary alkyl halide and follows S _ N 1 mechanis
Step-by-step solution
The substrate 2-bromo-2-methylpropane is a tertiary alkyl halide. Tertiary alkyl halides undergo nucleophilic substitution primarily via the S _ N 1 mechanism because the carbocation intermediate formed is highly stable due to inductive and hyperconjugation effects. The S _ N 1 mechanism involves the rate-determining step of carbocation formation, which is independent of the concentration of the nucleophile. Thus, the rate law is given by Rate = k[ Substrate ] . Polar protic solvents stabilize the carbocation inter