Aldol Condensation In some cases, the adducts obtained from the Aldol Addition can easily be converted (in situ) to α,β- unsaturated carbonyl compounds, either thermally or under acidic or basic catalysis. The formation of the conjugated system is the driving force for this spontaneous dehydration. Under a variety of protocols, the condensation product can be obtained directly without isolation of the aldol. The aldol condensation is the second step of the Robinson Annulation. Mechanism of the Aldol Condensation For the addition step see Aldol Addition Benzoin Condensation The Benzoin Condensation is a coupling reaction between two aldehydes that ...
Benzoin condensation The benzoin condensation is self condensation of Aromatic aldehydes to form an α-hydroxy ketone. The aromatic aldehyde is refluxed with alcoholic solution of potassium cyanide to form α-hydroxy ketone. Mechanism Following properties make cyanide a specific catalyst for the Benzoin condensation. (i) Cyanide ion have Sufficient nucleophilicity to add to carbonyl group. (ii) A marked acid strengthening effect on α–hydrogen atom of the cyanohydrin. (iii) The ability of cyanide ion as a leaving group to depart from the cyanohydrin in the last step. Thank you ...
The benzoin condensation is an addition reaction involving two aldehydes. The reaction generally occurs between aromatic aldehydes or glyoxals. The reaction produces an acyloin. In the classic application benzaldehydeis converted to benzoin CHEMICAL REACTION MACHANISM Addition of cyanide ion to create a cyanohydrin effects an umpolung to the normal Carbonyl charge affinity and the electrophilic aldehyde carbon becomes nuclephilic after deportonation. A thiazolium salt may also be used as the catalyst is this reaction A strong base is now able to deprotonate at the former carbonyl c- atom A second equivalent of aldehyde reacts with this carbanion; elimination of the ...
Benzoin Condensation O OH H - CN + CN /H O 2 H O OH- H OH OH OH CN - H CN OH O - H + CN Since cyanide is quite toxic, we will use thiamine as our catalyst to replace cyanide CH N NH Cl- 3 2 S N N + OH CH3 Thiamine is heat sensitive so the addition of 5 M NaOH needs to be added slowly (3 to 5 min) to the thiamine hydrochloride in an ice bath with constant swirling and maintain the temperature below room temperature. Once the benzaldehyde is added, the ...
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