How Long Is Rxn Of Nucleophile?

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How Long Is Rxn Of Nucleophile?

*substitution (of a carboxylic/acid derivative) = addition + elimination

- substitution at the tetrahedral intermediate from the addition of an organometallic to an aldehyde/ketone will not (usually) work as R- (i.e. H- or CH3-) is a bad leaving group
- addition of a Grignard reagent to an aldehyde/ketone = stable tetrahedral intermediate (alkoxide)
- addition of an alcohol to a carbonyl group in the presence of a base = unstable intermediate (hemiacetal/hydrate) - nucleophiles with good leaving groups (anions i.e. Cl-, RO-, RCO2-) = unstable - starting carbonyl compound with good leaving group = unstable (makes a Tetrahedral intermediate then collapses to form the starting carbonyl group) i.e. Grignard reagent added to an ester …show more content…
Stability: is RCOX electrophilic enough?
2. Nucleophilicity: good enough nucleophile?
3. Leaving Group Ability: X- (usually a halogen – on the acid) > Nu-

1. Carboxylic/Acid Derivative Stability
* C=O electrophilicity is increased by protonation (addition of acid)
2. & 3. Nucleophilicity & Leaving Group Ability
- Nu trends don’t necessarily apply for substitution at sp3 – carbon
- nucleophilicity increases by deprotonation
- leaving group ability increases by protonation

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