Methylene group

A methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon atom, which is connected to the remainder of the molecule by two single bonds.

This stands in contrast to a situation where the carbon atom is bound to the rest of the molecule by a double bond, which is preferably called a methylidene group, represented =CH2.

The name “methylene bridge“ can be used for the single-bonded isomer, to emphatically exclude methylidene.

The methylene group should be distinguished from the CH2 molecule called carbene.

This is because, owing to the structure, the carbon is especially acidic and can easily be deprotonated to form a methylene group.