MolSynapsequestion bank
MolSynapse / Question bank / Organic Reaction Mechanisms IV: Elimination / E1 mechanism and carbocation rearrangement
JEE Advanced levelSingle correct optionDifficulty 3 of 3o4017

Tert-butyl bromide solvolyses in ethanol at 25 C to give mainly ethyl tert-butyl ether (SN1) and some 2-methylpropene (E1), both from the same carbocation. Which change increases the fraction of 2-methylpropene?

  1. Araising the temperature of the reaction
  2. Bnone of these; the ratio depends only on carbocation stability
  3. Cadding a high concentration of a good non-basic nucleophile such as
  4. Dlowering the temperature

Answer: A

Both products come from the same cation, so the E1:SN1 ratio is set by the relative rates of proton loss and nucleophilic capture. Elimination has the higher activation energy and gains entropy (it makes an extra molecule), so raising the temperature increases the alkene fraction.
Practice Organic Reaction Mechanisms IV: Elimination More on E1 mechanism and carbocation rearrangement
Previous questionNext question

More questions on E1 mechanism and carbocation rearrangement