Carbenes, Types Structure & Stability

1.Carbenes can react as both electrophile as well as nucleophile.

  1. Bond angles are 125-140° for triplet methylene and 102° for singlet methylene. Both are sp2 hybridised with bent Shape.

3.In Triplet carbene, One nonbonding unpaired electron is present in p orbital and other in sp2 orbital

  1. Singlet carbene is similar to carbocation.

  2. Triplet carbene is the more stable state and Singlet is the excited state species

6.Substituents that can donate electron pairs e.g., halogens, may stabilize the singlet state by delocalizing the pair into an empty p-orbital. No Corresponding stabilisation possible for triplet carbene due to unavailibility of vacant orbital at carbon.

  1. When there is a substituent with lone pairs, the singlet carbene is generally more stable than the triplet carbene. Dichlorocarbene is more stable in singlet.


Order of stability of singlet carbene: :CH2 > :CF2 > :CCl2 > :CBr2 > :CI2

& Order of Stability of Triplet Carbene: :CI2 > :CBr2 > :CCl2 > :CF2



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