trimethylenemethane

Trimethylenemethane (often abbreviated TMM) is a chemical compound with formula . It is a neutral free molecule with two unsatisfied valence bonds, and is therefore a highly reactive free radical. Formally, it can be viewed as an isobutylene molecule with two hydrogen atoms removed from the terminal methyl groups.

== Structure == The electronic structure of trimethylenemethane was discussed in 1948. It is a neutral four-carbon molecule containing four pi molecular orbitals. When trapped in a solid matrix at about , the six hydrogen atoms of the molecule are equivalent. Thus, it can be described either as zwitterion, or as the simplest conjugated hydrocarbon that cannot be given a Kekulé structure. It can be described as the superposition of three states: {| |120x120px |120x120px |120x120px |} It has a triplet ground state (3A2′/3B2), and is therefore a diradical in the stricter sense of the term. Calculations predict a planar molecule with three-fold rotational symmetry, with approximate bond lengths 1.40 Å (C–C) and 1.08 Å (C–H). The H–C–H angle in each methylene is about 121°.