Question

Many reactions in organic chemistry involve mixing a filled orbital with an empty one to generate bonding and antibonding combinations, as in the diagram below. We have seen that the strength of such a bond is determined by delta E-the energy difference between the bonding orbital and the original filled one-and the number of electrons placed into the new molecular orbitals. Rank the four bonding partners a-d below in order from best to worst, in terms of the net stabilization that results from bond formation. Assume that all orbitals are on the same energy scale. You should consider the energy levels, shape, phase, and occupancy (# of electrons) of each potential bonding partner. Briefly explain your choices.

Answer 1

d -1

b - 2

a - 3

c - 4

Explanation: 'd' is the highest occupied molecular orbital (i.e. HOMO). So, it can give the most net stabilization that results from the bond formation.

'b' is the 2nd most stabilizing partner as it's having the same shape and same symmetry.

'a' is the 3rd most stabilizing partner as it's also having the same shape and same symmetry.

'd' is the least stabilizing partner as it has a different shape as well as symmetry to that of the best stabilizing partner.