Alkylation of Enolates

[@KaushikAdhikari]

11:02 an oversimplified explanation I was told: Bond energy C=O > C=C

[@VictortheOrganicChemistryTutor]

I've seen this explanation too but there's a problem with it: we can only rely on thermodynamic considerations like that if we're dealing with an equilibrium reaction, and this one is not an equilibrium. And the step is exothermic, so if we apply the Hammond postulate here, we're dealing with the early transition states, meaning that we care more about the enolate than the product. The *real* explanation is in the MO of the enolate. The HOMO orbital is a non-bonding orbital with a relatively high contribution from that carbon. Plus, we have lithium coordinating around oxygen, effectively "shielding" it from any electrophiles. There's also the HOMO-LUMO gap between the enolate and electrophile that we need to mind. Changing a leaving group does affect the outcome. This is truly where the C=O > C=C argument breaks apart. For instance, if you take an enolate and react with MeI, you get mostly C-substitution, but if instead you do the reaction with MeTf, you get way more of the O-substitution. Switch base to KH and add crown ethers, and boom, you have predominantly O-substitution!

[@KaushikAdhikari]

@VictortheOrganicChemistryTutor thank you for the clarification

[@KaushikAdhikari]

Please elaborate Stork Enamine Synthesis later on

[@VictortheOrganicChemistryTutor]

That's on my to-do list for this semester.