MolSynapsequestion bank
MolSynapse / Question bank / General Organic Chemistry III: Reaction Intermediates / Stability ranking of drawn radicals, carbanions and carbenes
JEE Advanced levelOne or more correct optionsDifficulty 3 of 3g3248

Which statements about the singlet carbene shown are correct? Select all that apply.

  1. AThe chlorine lone pairs donate into the empty p orbital and stabilise it.
  2. BIts two nonbonding electrons are unpaired with parallel spins.
  3. CIt adds to a cis-alkene stereospecifically to give a cis-substituted cyclopropane.
  4. DIts ground state is a singlet, with a lone pair in an sp orbital and an empty p orbital.

Answer: A, C, D

The carbene shown is dichlorocarbene. Lone-pair donation from the two chlorines into the empty p orbital favours the singlet ground state (statements 1 and 2). A singlet carbene adds to an alkene in a single concerted step, so the alkene geometry is retained: a cis-alkene gives the cis-1,1-dichlorocyclopropane (statement 3). Parallel unpaired spins describe a triplet carbene, so statement 4 is false.
Practice General Organic Chemistry III: Reaction Intermediates More on Stability ranking of drawn radicals, carbanions and carbenes
Previous questionNext question

More questions on Stability ranking of drawn radicals, carbanions and carbenes