A note on ad hoc explanations

It is quite common in organic chemistry to give ad hoc explanations of why an experiment has given an observed result. Sometimes, such proposals may give valuable suggestions as to further studies to probe mechanistic details. Sometimes, however, such explanations may be totally misleading when it is not realized that they are nothing else than speculations. 

In the reaction above, at least three hypothetical mechanistic explanations can be furnished, to fit any of the three different orders of introduction. 

The driving force to overcome the steric congention is the formation of the thermodynamically stable titanium dioxide. 

The moral of this is, that great care should be exercised in giving ad hoc explanations, especially if the experimental background is meager. 

The basis on which all strategies in organic synthesis are founded are the individual synthetic reactions. An overall plan for the construction of a complex target molecule may be ingenious and elegant, but it is sufficient that one single step fails for the whole plan to fail. To develop new reactions or to develop known reactions into reliable and efficient synthetic methods is therefore crucial to the art and science of organic synthesis. 

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