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Clemmensen reduction is a chemical reaction described as a reduction of ketones or aldehydes to alkanes using zinc amalgam and concentrated hydrochloric acid (HCl). [1] [2] This reaction is named after Erik Christian Clemmensen, a Danish-American chemist. [3] Scheme 1: Reaction scheme of Clemmensen Reduction.
This reaction sequence is thus a condensation reaction since there is a net loss of HCl when the two reactant molecules join. [7] Arrow-pushing mechanism for the Darzens reaction. If the starting halide is an α-halo amide, the product is an α,β-epoxy amide. [8] If an α-halo ketone is used, the product is an α,β-epoxy ketone. [2]
In organic chemistry, carbonyl reduction is the conversion of any carbonyl group, usually to an alcohol. It is a common transformation that is practiced in many ways. [1] Ketones, aldehydes, carboxylic acids, esters, amides, and acid halides - some of the most pervasive functional groups, -comprise carbonyl compounds.
First, kinetic studies of reactions between diazomethane and various ketones have shown that the overall reaction follows second order kinetics. [7] Additionally, the reactivity of two series of ketones are in the orders Cl 3 CCOCH 3 > CH 3 COCH 3 > C 6 H 5 COCH 3 and cyclohexanone > cyclopentanone > cycloheptanone > cyclooctanone.
These possibilities have been used to account for the fact that, for certain substrates like α-tetralone, the group that migrates can sometimes change, depending on the conditions used, to deliver either of the two possible amides. [8] Two proposed reaction mechanisms for the amide formation from a ketone via Schmidt reaction
Enantioselective ketone reductions convert prochiral ketones into chiral, non-racemic alcohols and are used heavily for the synthesis of stereodefined alcohols. [ 1 ] Carbonyl reduction, the net addition of H 2 across a carbon-oxygen double bond, is an important way to prepare alcohols.
The figure below illustrates one of the commonly accepted models for stereoselection without any modification to the Henry reaction. In this model, stereoselectivity is governed by the size of the R groups in the model (such as a carbon chain), as well as by a transition state that minimizes dipole by orienting the nitro group and carbonyl oxygen anti each other (on opposite sides of the ...
An aldol condensation is a condensation reaction in organic chemistry in which two carbonyl moieties (of aldehydes or ketones) react to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), and this is then followed by dehydration to give a conjugated enone. The overall reaction equation is as follows (where the Rs can be H)