In chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is R-(C:)-R’ or R=C: where the R represent substituents or hydrogen atoms. Methylene is the simplest carbene. The term “carbene” may also refer to the specific compound H2C:, also called methylene, the parent hydride from which all other carbene compounds are formally derived.Carbenes are classified as either singlets or triplets, depending upon their electronic structure. Most carbenes are very short lived, although persistent carbenes are known. One well-studied carbene is dichlorocarbene Cl2C:, which can be generated in situ from chloroform and a strong base. The two classes of carbenes are singlet and triplet carbenes. Singlet carbenes are spin-paired. In the language of valence bond theory, the molecule adopts an sp2 hybrid structure. Triplet carbenes have two unpaired electrons. Most carbenes have a nonlinear triplet ground state, except for those with nitrogen, oxygen, or sulfur, and halides substituents bonded to the divalent carbon. Substituents that can donate electron pairs may stabilize the singlet state by delocalizing the pair into an empty p orbital. If the energy of the singlet state is sufficiently reduced it will actually become the ground state.
Organic chemistry (GOC#14) #Comparative study of Electronic Effects.
This is comparative study of all major electronic effects. These major electronic effects are Inductive effect, Hyperconjugation effect and Resonance or Mesomeric effect.
Organic chemistry||GOC#11||Reaction intermediate #Carboanion #Carbanion.
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