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

Norman Lu; Vijayanath Elakkat; Joseph S Thrasher; Xiaoping Wang; Eskedar Tessema; Ka Long Chan; Rong-Jun Wei; Tarek Trabelsi; Joseph S Francisco

doi:10.1021/jacs.1c02570

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

J Am Chem Soc. 2021 Apr 14;143(14):5550-5557. doi: 10.1021/jacs.1c02570. Epub 2021 Mar 30.

Authors

Norman Lu^{1

2}, Vijayanath Elakkat¹, Joseph S Thrasher³, Xiaoping Wang⁴, Eskedar Tessema¹, Ka Long Chan¹, Rong-Jun Wei¹, Tarek Trabelsi⁵, Joseph S Francisco⁵

Affiliations

¹ Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106, Taiwan, ROC.
² Development Center for Smart Textile, National Taipei University of Technology, Taipei 106, Taiwan, ROC.
³ Department of Chemistry, Advanced Materials Research Laboratory, Clemson University, Anderson, South Carolina 29625, United States.
⁴ Neutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
⁵ Department of Earth and Environmental Science and Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6316, United States.

PMID: 33784456
DOI: 10.1021/jacs.1c02570

Abstract

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.