[1] During a telescoped second reaction or workup (step 2), the resulting negatively charged carbanion combines with an electrophilic Y to form the second covalent bond.
[citation needed] Unsubstituted and unstrained alkenes are typically insufficiently polar to admit nucleophilic addition, but a few exceptions are known.
The strain energy in fullerenes weakens their double-bonds; addition thereto is the Bingel reaction.
Bonds adjacent to an electron-withdrawing substituent (e.g. a carbonyl group, nitrile, or fluoride) readily admit nucleophilic addition.
Aromatic substituents, although typically electrophilic, can also sometimes stabilize negative charge; for example, styrene reacts in toluene with sodium to give 1,3-diphenylpropane:[8]