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How many of the following reactions give a major product predominantly via an elimination mechanism? (1) Ethyl chloride (CH3CH2Cl) treated with NaOCH3 / CH3OH (2) 2-chlorobutane (CH3CH2CHClCH3) treated with potassium tert-butoxide (t-BuOK)
- 0
- 1
- 2
- 3
Correct answer: 1
Solution
Reaction (1): Ethyl chloride is a primary alkyl halide. NaOCH3/CH3OH is a moderately basic, non-bulky nucleophile/base. Primary substrates strongly prefer SN2 over E2. Major product: CH3CH2OCH3 (SN2). Not elimination. Reaction (2): 2-Chlorobutane is a secondary alkyl halide. t-BuOK is a bulky strong base. Bulky bases cannot attack the carbon backside effectively (steric), so they abstract a beta-H via E2. Major product: but-2-ene (E2). This is elimination. Count = 1.
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