I'm confused as to how hyperconjugation can exist in trans alkene isomers. In order for this to happen the antibonding and bonding pi orbitals have to physically overlap - how is this possible? Also, how does hyperconjugation provide a stabilizing effect - does it make it so the double bonded carbons "think" there's 8 electrons around them/next to them all the time vs. only part of the time like with pi bonds?

I'm confused as to how hyperconjugation can exist in trans alkene isomers. In order for this to happen the antibonding and bonding pi orbitals have to physically overlap - how is this possible? Also, how does hyperconjugation provide a stabilizing effect - does it make it so the double bonded carbons "think" there's 8 electrons around them/next to them all the time vs. only part of the time like with pi bonds?

 

What is confusing about hyperconjugation in trans isomers specifically? I don't see how it would be different in cis isomers. The interaction happens from the sigma bond beta to the sp2 carbon so the location of the substituent on the other side of the alkene should only make a negligible difference with respect to the orbital overlap comprising the hyperconjugation.

What do you mean with the beta part? The depictions in my book of pi bonds involve the two electrons on the same side of whatever axis they sit in. So if it's a vertical one (2py), both electrons are in the up (or down) side - they can't cross because the sigma bond is in the way. So if there are two methyl groups that are trans, then one of them interacts with an antibonding molecular orbital that physically overlaps the filled 2py orbital, whereas the other one interacts with the antibonding molecular orbital that physically overlaps an empty 2py orbital. Overlapping empty or one empty and one filled, orbitals don't bother me, but how can there be >2 e- in any one spot, like there would be with the first one?