More Electropositive is More Electronegative: Atom Size Determines C=X Group Electronegativity.

Chemistry

Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit Amsterdam, De Boelelaan 1108, 1081 HZ, Amsterdam, The Netherlands.

Published: March 2024

AI Article Synopsis

  • The C=X group can become more electronegative as the electronegativity of atom X decreases down Groups 16, 15, and 14 of the Periodic Table.
  • Our quantum-chemical analyses show that this increase in electronegativity is due to the larger size of atom X as it moves down a group.
  • This knowledge can help enhance the hydrogen-bond donor strength of amides by effectively withdrawing density from the NH group, with H NC(=SiR )R proving to be a stronger hydrogen-bond donor than H NC(=CR )R.

Article Abstract

Opposite to what one might expect, we find that the C=X group can become effectively more, not less, electronegative when the Pauling electronegativity of atom X decreases down Groups 16, 15, and 14 of the Periodic Table. Our quantum-chemical analyses, show that, and why, this phenomenon is a direct consequence of the increasing size of atom X down a group. These findings can be applied to tuning and improving the hydrogen-bond donor strength of amides H NC(=X)R by increasingly withdrawing density from the NH group. A striking example is that H NC(=SiR )R is a stronger hydrogen-bond donor than H NC(=CR )R.

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Source
http://dx.doi.org/10.1002/chem.202304161DOI Listing

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