Controversy in Chemistry: What Counts as Evidence?—Two Studies in Molecular Structure

Hindsight is a wonderful thing : Controversies are always difficult to characterize while they are in progress; however, as shown for the cases of stereochemistry and bond‐stretch isomerization, it is much easier once all the evidence has been amassed. These two examples have demonstrated how important it is to consider all the experimental results before coming to a conclusion. The second example shows above all that some evidence is more equal than others—crystal‐structure analysis was considered at all stages to be the most reliable.