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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.
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.
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]
Robinson annulation is one notable example of a wider class of chemical transformations termed Tandem Michael-aldol reactions, that sequentially combine Michael addition and aldol reaction into a single reaction. As is the case with Robinson annulation, Michael addition usually happens first to tether the two reactants together, then aldol ...
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.
This class of reactions is a vital part of life as it is essential to the formation of peptide bonds between amino acids and to the biosynthesis of fatty acids. [4] Idealized scheme showing condensation of two amino acids to give a peptide bond. Many variations of condensation reactions exist.