Diff: 2 64) Explain why the free rotation about the carbon-carbon bond in CH3CH3 is not present in CH2CH2. Answer: The hybridization of the oxygen atom is sp2 and the OCH bond angle is approximately 120°. 63) Provide the hybridization of oxygen in acetaldehyde (CH3CHO) and estimate the OCH bond angle.Now each carbon atom is left with one ‘p’ orbital (say p z) unhybridised. In the formation of CH 2 = CH 2 each carbon atom in its excited state undergoes sp 2 hybridisation by intermixing one s-orbital (2s) and two p-orbitals (say 2p x, 2p y) and reshuffling to form three sp 2 orbitals.