Ketones And Aldehydes Flashcards
What are the types of attacks that a carbonyl group C=O undergo?
1) If product stable, reaction stops here: Nucleophilic Addition to C=O
2) If R 1 good leaving group: Nucleophilic Substitution to C=O (only for COOH)
3) If Nuc has lone pair- loses OH: Nucleophilic Substitution + Replacement of O
What does nucleophilic addition of C=O involve?
*movement of pi bond of the C=O
*Reduction with NaBH 4 /LiALH 4 , Grignard reaction
What does the nucleophilic substitution + replacement of O entail?
Generally 2-step reaction = addition-elimination reactions
Reactions of aldehydes and ketones: usually with a N based nucleophile
Enols and enolates: why is a hydrogen alpha to a C=O acidic?
*inductive effect by electron withdrawal results in C-H bonds being weakened
* Delocalisation of the resulting negative charge stabilises the enolate and favours its formation
- a second C=O to stabilise carbocation
What is tautomerism?
isomerisation occurring by the migration of a proton and the
movement of a double bond. The isomers that interconvert are called tautomers
How do reactions differ based on whether they occur under basic or acidic conditions (enols + enolates)?
- Reactions under base-conditions occur via the
enolate - Reactions under acidic-conditions occur via the enol
- Very small amounts of the enol form is present
How do ketones preform in condensation (aldol reactions) compared to aldehydes?
Reaction very poor:
* Ketones are less reactive than
aldehydes as electrophiles
* The product from ketone self-
condensation is more sterically
compressed\equilibrium favours the
starting material
all the reactions with drawings?
*make mind maps + revise them
