Topic a2 - Carbanions

is all exo-tet favoured / disfavoured

favoured

all exo-trig favoured / disfavoured

favoured

5- and 6- endo-tet favoured / disfavoured

disfavoured

3-, 4-, 5- endo-trig favoured / disfavoured

disfavoured

6-, 7- endo-trig favoured / disfavoured

favoured

all endo-dig favoured / disfavoured

favoured

3-, 4- exo-dig favoured / disfavoured

disfavoured

5- to 7- exo-dig favoured / disfavoured

favoured

what is an exo ring cyclisation

bond breaks outside ring

what is an endo ring cyclisation

bond breaks inside ring

Carbanions act as _________

Nucleophiles

-I effects ______ a carbanion

Stabilises

+I effects _______ a carbanion

Destabilises

In a more stable carbanion the conjugate acid has a _____ pKa

lower

more s character in an orbital ____ the pKa

lowers

4 ways of forming carbanion

Grignards, Organolithium, Organocuparates and decarboxylation (forming enolates)

Carbanions don’t ____ but they do _____

rearrange, fragment