Conjugated alkenes can be electrophilic
المؤلف:
Jonathan Clayden , Nick Greeves , Stuart Warren
المصدر:
ORGANIC CHEMISTRY
الجزء والصفحة:
ص499-500
2025-06-09
533
Conjugate additions occur only when the C=C double bond is immediately adjacent to the C=O group. They don’t occur to C=C bonds that aren’t conjugated . Compounds with double bonds adjacent to a C=O group are known as α,β-unsaturated carbonyl compounds. Many α,β-unsaturated carbonyl compounds have trivial names, and some are shown here. Some classes of α,β-unsaturated carbonyl compounds also have names such as ‘enone’, made up of ‘ene’ (for the double bond) + ‘one’ (for ketone).
Most types of nucleophiles can be made to undergo conjugate additions with α,β-unsaturated carbonyl compounds, and seven examples are shown below. Note that many of these nucleophiles would not add to a simple carbonyl group: we will explain why shortly. Conjugate addition is also known as Michael addition, and the reactive α,β-unsaturated carbonyl compounds shown here are often known as Michael acceptors.
The reason that α,β-unsaturated carbonyl compounds react differently is conjugation. There we introduced you to the idea that bringing two π systems (two C=C bonds, for example, or a C=C bond and a C=O bond) close together leads to a stabilizing interaction. It also leads to modified reactivity, because the π bonds no longer react as independent functional groups but as a single, conjugated system.
●Conjugation makes alkenes electrophilic
• C=C double bonds are nucleophilic
• C=C double bonds conjugated with carbonyl groups can be electrophilic
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