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Chemistry · Glossary

What is Singlet and triplet carbenes?

Also known as: singlet carbene · triplet carbene

Definition 27.8 University Chemistry — Year 3 · Chapter 27 — Radicals, Carbenes and Rearrangements

A singlet carbene has its two non-bonding electrons paired in one orbital, an sp2sp^2 hybrid, its p orbital empty; a triplet carbene has them unpaired, one in each orbital, with parallel spins.

Electron occupations of the two non-bonding orbitals of a carbene. The triplet is the ground state of CH2; π-donor substituents (Cl, OR, NR_2) raise the p orbital and make the singlet the ground state, as in dichlorocarbene.
Electron occupations of the two non-bonding orbitals of a carbene. The triplet is the ground state of CHX2\ce{CH2}; π\pi-donor substituents (Cl, OR, NR2\mathrm{NR_2}) raise the p orbital and make the singlet the ground state, as in dichlorocarbene.
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