One Theory That Requires Exceptions To The Woodward Hoffmann Rules.

Why do the WH rules work? The usual argument is that a +signed function must overlap with another +signed function, and from that observation, the rotational characteristics of the WH rules follow. (Actually, the same rules follow if a bond forms only when plus interferes with minus, but the diagrams are more messy. This is actually the rule for forming antisymmetric wave functions, which at least in some formalisms is a requirement for the Exclusion Principle, but since the same outcome always arises, this issue is irrelevant here.) This gets to the point where we have to ask, what does the sign mean?

In general theory of wave interference it refers to the phase of the wave. When amplitudes have the same sign, they reinforce. The important point is there must be a phase relationship between the ends. Now, the phase of the wave is proportional to the action, and it changes because the action (the time integral of the Lagrange function) evolves in time. However, no matter how long zero is integrated with respect to time, you still get zero, and the Lagrange function of an entity with zero mass and zero charge, which is what an empty orbital has, is zero. The solution to the Schrodinger equation when E, V and m each equal zero is zero everywhere in all time. Zero can be added any number of times, but it makes no difference.

If so, the canonical structure with positive charge on an end carbon atom gives zero directional effect. Therefore, the strength of the preference (because there is always

Now, I believe this alternative interpretation is important for two reasons. The first is, it gives a specific reason why there should be exceptions to the Woodward Hoffmann rules, and it predicts where they will be found. Thus if nothing else, it will guide further experimental work. The alternative theory is either right or wrong, and there is one obvious way to find out. The second reason is more important: I believe that if this alternative interpretation is found to be correct, it forces chemists to revisit the concept canonical structures, which I believe gives far more fertile ground for understanding chemistry than the current MO theory, at least for the average bench chemist. Further, I suspect there are no aspects of organic chemistry (and probably not of other chemistry, except I am not familiar enough with that to be sure) that does not comply with the concept of canonical structures, if these are properly used. So, there is a further challenge: find some aspect of chemistry where canonical structures, properly used, fail.

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