Soft Base
| Also Known As | Class B Lewis base, polarizable Lewis base, HSAB soft base |
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What is Soft Base?
In HSAB theory, a Lewis base that is large, highly polarizable, and of low electronegativity. Soft bases prefer to bond with soft acids. Examples include S²⁻, RS⁻, CO, CN⁻, and phosphines. They are easily oxidized and have high electron density in diffuse orbitals.
Properties & Characteristics
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
In HSAB theory, a Lewis base that is large, highly polarizable, and of low electronegativity. Soft bases prefer to bond with soft acids. Examples include S²⁻, RS⁻, CO, CN⁻, and phosphines. They are easily oxidized and have high electron density in diffuse orbitals.
Soft bases serve as ligands in coordination complexes used in homogeneous catalysis. Phosphine ligands (soft bases) stabilise transition metal catalysts in organic synthesis. Antidotes for heavy metal poisoning (chelation therapy) work by acting as soft bases to sequester soft acid metal ions.
Some soft bases are toxic, such as CO (carbon monoxide) and cyanide. Thiol compounds often have strong, unpleasant odours and may be toxic. Appropriate fume hood use is essential.