Orgo Chapter 6

Mechanisms

Energy diagrams reveal

relative stabilities of reactants and products, intermediates, activation energies (slow and fast)

reaction rates

kinetics refers to

thermodynamics

refers to equilibrium (stabilities) of reactants and products

Nucleophiles

electron rich, lone pair (with or without a negative charge), can be a pi bond or sigma bond; they attack electrophiles

Electrophiles

electron deficient, polar bond, full positive charge; compound being attacked by nucleophiles

the arrow points to atom or area where new bond will be

To show bond formation

the tail of arrow begins in center of bond

To show bond breaking

Nucleophilic attack, loss of leaving group, proton transfers, Carbocation rearrangements

4 basic mechanism steps

1,2-hydride shift

carbocation rearrangement where H-atom AND its electrons shift

1,2-methyl shift

CH₃ AND its electrons shift

methyl < 1° < 1° w/ resonance ~ 2° < 2° w/ resonance ~ 3° < 3° w/ resonance

order of stability

allylic

position adjacent to a double bond

benzylic

first carbon off a benzene ring

inductive effect and hyperconjugation

Reasons for C+ stability/rearrangements

Predicting C+ rearrangements

look to each adjacent carbon to the C+ (more substituted? closer to a double bond? allylic or benzylic?). consider each shift (hydride or alkyl)