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Neutron Diffraction Study of Significant sp3 and sp2 C–H Bond Shortening in a Fluorinated Pyridinium Saccharinate...

Publication Type
Journal Name
Journal of the American Chemical Society
Publication Date
Page Numbers
5550 to 5557

We have experimentally shown by neutron diffraction significant shortening of both sp3- and sp2-hybridized C–H bonds to 1.092(2) and 1.081(1) Å in a hydrogen-bonded crystal of a difluorinated compound, 4-((2,2-difluoroethoxy)methyl)pyridinium saccharinate. Both MP2 and DFT calculations affirmed the C–H bond shrinkages. Sanderson’s electronegativity equalization principle provides insight into the shortening of the C–H covalent bond lengths for both sp3- and sp2-hybridized carbon atoms. To the best of our knowledge, this neutron diffraction study has revealed the largest extents of sp3 and sp2 C–H bond shrinkages with a 3-sigma rule being satisfied.