Structural formula of some compounds having methylene group: dichloromethane (top left), methylene cyclopropene (middle upper), singlet carbene (upper right), malonate ester (lower left) and propane (lower right).
A methylene group is a common structural element in organic chemistry, with the gross formula CH2. The methylene group may contain both double bonded (= CH2) and single-linked (-CH2-). The double-bonded methylene is sometimes referred to as the term methylidene. Reactivity and properties
Methyle never occurs as an independent molecule, but is part of numerous organic compounds, including cyclic compounds. An exception is the triplet carbene, which is a highly reactive and short lived connection.
Most methylene groups that form part of ordinary hydrocarbons are non reactive. They undergo some radical halogenation. However, there are many more reactive methylenes, such as methylene in diethylmalonate. The hydrogen of the methylene unit between the two esters are very acidic (pKa = 11) and can be easily deprotonated. Also see
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