How does methylcarbene rearrange to form ethylene?

Methylcarbene undergoes an intramolecular rearrangement to form ethylene through a 1,2-hydrogen shift. In this process, a hydrogen atom migrates from one carbon atom to the adjacent carbon atom, allowing the carbene to transition into a stable molecule where the carbon atom achieves its normal, tetravalent state.1

This type of rearrangement is classified as an intramolecular reaction, meaning it involves only the carbene itself and requires no external substances. Such shifts are structurally possible for carbenes like methylcarbene but are not possible for simpler carbenes composed of only three atoms, such as methylene or the halomethylenes.1