Use FMO theory to rationalize the different stereospecificity of S_N1 and S_N2 reaction mechanisms.

Question

Quizplus · Accepted Answer

The Answer is S_N2 reactions are stereospecific because the HOMO of the nucleophile (often a nonbonding orbital)must interact with the LUMO of the electrophile (often an antibonding molecular orbital)with the correct symmetry.This can occur only with inversion of stereochemistry.An S_N1 reaction proceeds via a planar carbocation intermediate,in which the LUMO is an empty p orbital.The HOMO of the incoming nucleophile can thus interact with either lobe of the p orbital,so a racemic mixture of enantiomers will be obtained.

Use FMO Theory to Rationalize the Different Stereospecificity of SN1

Use FMO Theory to Rationalize the Different Stereospecificity of S_N1