Sir,what is the HOMO for allylic radical (●C3H5) in photochemical condition ?Is it ¥3 ,ie 3unpaired electron in 3 MO,?I can't understand symmetry of HOMO for this radical in{1,3} shift in photochemical condition,, please sir explain it.
Yes, under photochemical condition, due to electronic excitation to Psi-3, it becomes HOMO that has plane of symmetry. For more details about how to make Huckel molecular orbital diagram along with some tricks please visit to my another video the link of which is given below: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-DfvNxbfAlZg.html
sir i didn't understand in 1,3 shift,allylic carbon has only 2 pi electrons or 1 double bond it means it it chi1 in homo thermal cond so how t has node and c2 symmetry
Dear Ravina, Thank you for watching this video. For the explanation it is assumed that the reaction is passing through the allyl radical. In allyl radical there are 3 pi electrons distributed over 3 carbon atoms. Under thermal condition Psi 2 will be HOMO with C2 symmetry.
The [1,3]-migration of hydrogen is antarafacial under thermal condition involving a transition state which is very strained (unstable). Because of that it is not feasible thermally.
