Which alkyl halide would react fastest by the SN1 mechanism?
Correct answer: D. (CH3)3CBr
- A. CH3Br
- B. CH3CH2Br
- C. (CH3)2CHBr
- D. (CH3)3CBr
Explanation
SN1 rates follow the stability of the carbocation formed, and that increases from primary through secondary to tertiary because each alkyl group releases electron density and spreads the charge. The tertiary bromide therefore ionises most readily. The order is exactly reversed for SN2, where the methyl halide reacts fastest because it is the least hindered.
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About Nucleophilic Substitution
Nucleophilic substitution replaces a leaving group in an alkyl halide when an electron-rich nucleophile attacks the carbon atom. The topic compares SN1 and SN2 mechanisms, including reaction conditions, substrate structure, solvent effects, nucleophile strength, carbocation formation and stereochemical changes, and distinguishes substitution from elimination.
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