# Question #c0d21

Nov 4, 2017

An active methylene group is a carbon with a lone pair of electrons stabilised by resonance. It is a good nucleophile, and so reacts with an electrophilic carbon in the Michael Addition.

#### Explanation:

A base removes a proton from a methylene, leaving a lone pair of electrons on the carbon. The lone pair of electrons is stabilised by resonance:

It is called an active methylene because the carbon is now an excellent nucleophile, and is very reactive. The nucleophilic carbon reacts with an electrophilic carbon in another molecule. This is the basis of the Michael Addition.

An example of a Michael Addition is shown below:

The active methylene is a good nucleophile and thus reacts with the electrophilic $\beta$-carbon.