What is the hybridisation of carbon atom in carbanion
The Correct Answer and Explanation is:
The hybridization of the carbon atom in a carbanion depends on the structure of the anion. In a simple carbanion, the carbon atom carries a negative charge, which means it has one extra electron compared to its neutral state. This extra electron affects the electron configuration and hybridization of the carbon atom.
In most simple carbanions, such as the methyl anion (CH₃⁻), the carbon atom undergoes sp³ hybridization. Here’s why:
- Electron Configuration: A neutral carbon atom has the electron configuration 1s² 2s² 2p². When it gains an extra electron (as in a carbanion), it has a total of 8 electrons, including the lone pair on carbon.
- Bonding and Geometry: The carbon atom in the carbanion typically forms three bonds with other atoms (like in CH₃⁻, where it bonds to three hydrogen atoms). The fourth electron (the extra one from the anion charge) occupies a lone pair in the hybridized orbital.
- Sp³ Hybridization: In sp³ hybridization, one 2s orbital and three 2p orbitals combine to form four equivalent hybrid orbitals. These orbitals are directed toward the corners of a tetrahedron, allowing the carbon atom to form bonds with three other atoms and hold the lone pair in the fourth orbital. This geometry is consistent with the tetrahedral shape seen in the carbanion.
- Resulting Structure: The carbon in the carbanion adopts a tetrahedral geometry with bond angles close to 109.5°, and the extra electron occupies one of the sp³ hybrid orbitals, contributing to the negative charge.
Thus, the carbon atom in a typical carbanion is sp³ hybridized. However, the hybridization can change if the carbanion is part of a structure with different bonding or resonance, such as in alkynyl anions (C≡C⁻) or resonance-stabilized carbanions like the acetylide anion, where sp hybridization might be observed.
