hard base 

Also contains definition of: soft base
https://doi.org/10.1351/goldbook.H02742
A Lewis base with a donor centre (e.g. an oxygen atom) of low polarizability the converse applies to soft bases.
See also: hard acid
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1120 [Terms] [Paper]
Citation: 'hard base' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.H02742 RIS BibTex EndNote
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Last revised: February 24, 2014