Electronic Transition Expected in HCHO
Electronic Transition Expected in Formaldehyde
In formaldehyde, each C-H bond arises by the linear overlap of sp2 orbital of carbon and 1s orbital of H atoms. Hence, C-H bonds are sigma bonds. A sigma bond between carbon and oxygen atoms arises by the linear overlap of sp2 orbital of carbon atom and sp orbotal of oxygen atoms and a ℼ-bond by the lateral overlap of 2px and 2py orbitals-
The oxygen atom has two lone pairs of electrons- one 2py orbital and other in sp orbital. The lone pair present in 2py orbital can coordinate due to greater p-character because the dumb bell p-orbital is more extended in space than the spherical s-orbital.
From the molecular orbital diagram, it is clear that forma;dehyde shows two transitions in uv-vis spectra. π → π* at 185nm and n → π* at 270nm. The latter has two lower intensity than the former due to forbidden nature.
Electronic Transition Expected in Ethene
Electronic Transition Expected in Butadiene
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