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