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Chemistry LibreTexts

Active Methylene Compound

An active methylene compound is a compound that has the following general structural formula.

 

 

E1, E2 = a functional group that withdraws electrons by resonance

 

eg:

 

activemethylenecompound2.png

 

The conjugate base of an active methylene compound is highly resonance stabilized.

eg:

 

activemethylenecompound3.png

 

Consequently, active methylene compounds are highly acidic and can be deprotonated, for all practical purposes, irreversibly, using common strong bases, such as the hydroxide ion or alkoxide ions.

 

activemethylenecompound4.png

 

Notice that the equilibrium constant, K, is very large.

 

activemethylenecompound5.png