The carbonyl carbon atom found in aldehydes and ketones is ____________?
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Answer: B. sp2 hybridised
Explanation
The carbonyl carbon atom in aldehydes and ketones forms a double bond with oxygen and two single bonds with other groups. VSEPR theory dictates that three regions of electron density around this carbon adopt a trigonal planar geometry. Hybridization models confirm that forming three sigma bonds requires sp2 hybridization of the central carbon atom. Carbonyl groups consist of a carbon-oxygen double bond that is highly polarized due to oxygen electronegativity. Trigonal planar molecular geometry results in bond angles of approximately 120 degrees around the central carbon. Unused p-orbital electrons on the carbon and oxygen atoms overlap sideways to form the secondary pi bond.
An sp3 hybridized carbon adopts a tetrahedral geometry with four single bonds, unlike the trigonal planar carbonyl carbon. An sp hybridized carbon forms linear geometries with triple bonds or two double bonds, which does not fit carbonyls. Claiming the carbon is unhybridized ignores the established quantum mechanical model of covalent bonding in organic molecules.
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