AllChemicals — The Online Chemical Glossary | https://allchemicals.info/chemical/741-soft-acid
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Also Known As
Class B Lewis acid, polarizable Lewis acid, HSAB soft acid
What is Soft Acid?
In HSAB theory, a Lewis acid that is large, has low positive charge or zero charge, and is highly polarizable. Soft acids prefer to bond with soft bases. Examples include Cu⁺, Ag⁺, Au⁺, Hg²⁺, and Pt²⁺. They prefer thiolate (S) donors over hard oxygen donors.
Properties & Characteristics
A soft acid (in HSAB theory) is a Lewis acid with a large, polarizable electron cloud, low positive charge density, and high electronegativity. Soft acids preferentially bind to soft bases through covalent interactions rather than electrostatic ones. Examples include Hg²⁺, Pt²⁺, Ag⁺, and Au³⁺. The HSAB principle predicts that soft acids bind more strongly to soft bases.
Uses & Applications
HSAB theory using soft acid concept guides ligand selection in coordination chemistry and catalyst design. Soft acid metals like platinum are used as anticancer drugs (cisplatin). Understanding soft acid character predicts heavy metal toxicity through binding to biological soft bases like sulfur in proteins.
Safety Information
Many soft acids are toxic heavy metal ions (mercury, lead, cadmium) that bind irreversibly to biological molecules. Platinum compounds used in chemotherapy have significant side effects requiring careful medical management.
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
SynonymsClass B Lewis acid, polarizable Lewis acid, HSAB soft acid
Frequently Asked Questions
In HSAB theory, a Lewis acid that is large, has low positive charge or zero charge, and is highly polarizable. Soft acids prefer to bond with soft bases. Examples include Cu⁺, Ag⁺, Au⁺, Hg²⁺, and Pt²⁺. They prefer thiolate (S) donors over hard oxygen donors.
HSAB theory using soft acid concept guides ligand selection in coordination chemistry and catalyst design. Soft acid metals like platinum are used as anticancer drugs (cisplatin). Understanding soft acid character predicts heavy metal toxicity through binding to biological soft bases like sulfur in …
Many soft acids are toxic heavy metal ions (mercury, lead, cadmium) that bind irreversibly to biological molecules. Platinum compounds used in chemotherapy have significant side effects requiring careful medical management.
Editorial standards: Chemical data is sourced from peer-reviewed literature,
CAS Registry, NIST WebBook, and PubChem. Safety information reflects guidance from OSHA, ECHA,
and IAEA. For educational purposes only — always consult official SDS documentation and qualified
professionals before handling chemicals.
