Mechanism
The Henry reaction begins with the deprotonation of the nitroalkane on the α-carbon position forming a resonance stabilized anion. This is followed by alkylation of the nitroalkane with the carbonyl containing substrate to form a diastereomeric β-nitro alkoxide. The protonation of the alkoxide by the previously protonated base will yield the respective β-nitro alcohol as product. (Scheme below)
It is important to note that all steps of the Henry reaction are reversible. This is due to the lack of a committed step in the reaction to form product. It is for this reason that research has been geared towards modifications to drive the reaction to completion. More information about this can be found in the modification section of this article.
Read more about this topic: Nitroaldol Reaction
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