Alpha halogenation

alpha halogenation allows for what

conversion of ketone/aldehyde to alpha beata unsaturated carbonyl compounds

always has these reactants with the ketone/aldehyde

1) Br2,CH3COOH

2)K+,Otbu,t-buOH

alpha halogenation reactants and products

reactants

• carbonyl compound

• 1) Br2,CH3COOH

• 2)K+,Otbu,t-buOH

products

• alkene foms from alpah to beta hydrogen????

enols pros

Form under very mild conditions (acid or base catalysis).

enols cons

Only form in small amounts (low concentration at equilibrium).

Formation is controlled by equilibrium (keto form is usually favored).

enolates pros

More reactive than enols (because of the negative charge).

Can be formed 100% (full conversion)

enolate cons

Requires a very strong, non-nucleophilic base to form completely (like LDA).

LDA

very bulky base thats nout nucleophilic adn is soluble in THF

what can be done with enolate

make C-C bonds

enolate is a nucleophile that does SN2 subsitution

can be a electrophile but..

• must have good L.G.

• primary or methyl substrate

With LDA: you can alkylate

ketones,esters, and nitriles

what type of enolate in low temps

kinetic enolate

what is the major product for kinetic enolates

double bond on the less sub. enolate

Thermodynamic Enolate conditions

Weaker base (like RO⁻), room temperature, reversible reaction.

regiochemistry for thermodynamic enolate

double bond on the more substituted enolate

malonic ester synthesis products adn reactants

reactants

• malionic ester

• NaoEt for every alkyl halide

• at least 1 alkyl halide

• H3O+

• heat

product

• only half of the malonic ester (and replace one OEt with OH and replace the other side with 1 or both R groups)