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This is a question for the physical chemists out there.

For a given chemical reaction there is a barrier to traverse in order to proceed from reactants to products. Reactants e.g. an organic base abstracting a proton can approach each other at different orientations - attack angles. At times, this orientation will lead to better orbital overlap between the lone pair on the base and the s orbital of the hydrogen. I have heard people talk about better orbital overlap, lowering/narrowing the barrier to reaction. Is this a valid way of conceptualizing this? Does better orbital overlap change the barrier? I personally have always associated a better overlap as starting further along the reaction coordinate/barrier, not the actual barrier itself being altered?

Any thoughts from the physchems?

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According to the typical (covalent) bond theory, when two orbitals approach, the forming "bonding" orbital has lower energy and the "anti-bonding" orbital has higher energy. The stabilization depends on the overlap between the orbitals (among other things). Therefore if you have up to two electrons available, the energy of the system will decrease by forming a bond. Now if you have two pathways to proceed in a reaction, the pathway implying maximal overlap between the orbitals will be the minimal energy reaction pathway, approximately.

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