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A crossed aldol condensation is a result of two dissimilar carbonyl compounds containing α-hydrogen(s) undergoing aldol condensation. Ordinarily, this leads to four possible products as either carbonyl compound can act as the nucleophile and self-condensation is possible, which makes a synthetically useless mixture.
In contrast, retro-aldol condensations are rare, but possible. [14] This is the basis of the catalytic strategy of class I aldolases in nature, as well as numerous small-molecule amine catalysts. [15] When a mixture of unsymmetrical ketones are reacted, four crossed-aldol products can be anticipated: Crossed aldol (addition) reaction
Intramolecular aldol condensation is between two aldehyde groups or ketone groups in the same molecule. Five- or six-membered α , β -unsaturated ketone or aldehydes are formed as products. This reaction is an important approach to the formation of carbon-carbon bonds in organic molecules containing ring systems.
It is prepared by the aldol condensation of acetone to give diacetone alcohol, which readily dehydrates to give this compound. [4] [5] Phorone and isophorone may be formed under the same conditions. Isophorone originates via a Michael addition: Phorone is formed by continued aldol condensation:
In organic chemistry, the Claisen–Schmidt condensation is the reaction between an aldehyde or ketone having an α-hydrogen with an aromatic carbonyl compound lacking an α-hydrogen. It can be considered as a specific variation of the aldol condensation .
The Perkin reaction is an organic reaction developed by English chemist William Henry Perkin in 1868 that is used to make cinnamic acids.It gives an α,β-unsaturated aromatic acid or α-substituted β-aryl acrylic acid by the aldol condensation of an aromatic aldehyde and an acid anhydride, in the presence of an alkali salt of the acid.
Enones are typically produced using an aldol condensation or Knoevenagel condensation. Some commercially significant enones produced by condensations of acetone are mesityl oxide (dimer of acetone) and phorone and isophorone . [5] In the Meyer–Schuster rearrangement, the starting compound is a propargyl alcohol.
Crotonaldehyde is produced by the aldol condensation of acetaldehyde: 2 CH 3 CHO → CH 3 CH=CHCHO + H 2 O. Crotonaldehyde is a multifunctional molecule that exhibits diverse reactivity. It is a prochiral dienophile. [5] It is a Michael acceptor. Addition of methylmagnesium chloride produces 3-penten-2-ol. [6]