Curious or dubious: the story of a hydrocarbon with an exceptionally short C=C bond length

摘要

One of the greatest achievements in molecular sciences this century has been the accurate determination of structures of a large number of chemical systems. While a variety of spectroscopic and diffraction methods have been used successfully for this purpose, X-ray crystallography has led the way. For the vast majority of chemists, single crystal X-ray structure determination represents the ultimate unimpeachable evidence for the proposed structure. The geometric details obtained through crystallography have also served as the basis for our present understanding of structural chemistry. These data represent an important source of parameterization as well as benchmarks for empirical theoretical models. The quality of quantum chemical procedures, which often use drastic approximations while solving the Schrodinger equation, has also been judged through comparisons of structural predictions with X ray results.