orgo ch6

nucleophilic substituation reaction

electrophilic carbon and nucleophilic atom make new bond

leaving group

halogen or oxygen group

sn1 step

leaving group leaves, formation of carbocation is rate determining step, undergo rearrangement hydride shift or ring expansion, nucleophile attack electrophile carbon, if chiral center then pair of enantiomers form

product formation depends on stability of carbocation

late ts carbocation like product, early ts carbocation like reactant

inductive effect- stability of carbocation

electronic effect due to polarization of sigma bonds within molecule

hyperconjugation- stability of carbocation

sigma bonding electron of ch bond fill empty p orbital of e deficient c

resonance- carbocation stability

tertiary greater than secondary greater than primary benzyl
tertiary greater than secondary greater than primary allylc

rate determining step

formation of carbocation

solvolysis

solvent itself act as nucleophile

nuclephile, best nucleophile

electron donating, neg charge, large size, less steric hinderence

sn1 reaction

nucleophile substitution at carbon with 4 single bonds, weak bases are good leaving group

weak bases

stronger acid will have weak conjugate base

sn1 final product stereochem

formation of product with chiral center, which form a pair of enantiomers

carbocation rearrangment

alkyl carbocation undergo rearrangement to form stable carbocation

ring expansion

rearrangement to relieve ring strain

sn2 reactions

bimolecular reactions, one step reactions, break bond and forming bond happen at same time, inversion of configuration at electrophile carbon

leaving group for sn2 reaction

stronger base is better leaving group

nature of substrate for sn2

methyl, primary benzylic and allylic, secondary benzylic and allylic

base strength of sn2

stronger base has weaker conjugate acid

polarizability of sn2

large size nucleophiles are better than smaller

steric factors sn2

bulky nucleophiles disfavor sn2 reactions

sn2 polar aprotic solvent

pyridine

sn2 polar aprotic solvent

tetrahydrofuran