Hard-Soft Acid-Base (HSAB) Calculator

Predict Acid-Base Interactions and Reaction Favorability

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Chemical Hardness Calculator

Calculate absolute hardness and softness parameters.

Hardness Parameters: -

HSAB Interaction Predictor

Predict reaction favorability based on HSAB principle.

Interaction: -

Understanding HSAB Principle

Basic Concepts

The HSAB principle states:

  • Hard Acids: Small size, high charge, low polarizability
  • Soft Acids: Large size, low charge, high polarizability
  • Hard Bases: Small size, high electronegativity
  • Soft Bases: Large size, low electronegativity

Interaction Rules

Key principles:

  • Hard-Hard: Ionic bonding preferred
  • Soft-Soft: Covalent bonding preferred
  • Hard-Soft: Less favorable interactions
  • Borderline: Can interact with both

Applications

HSAB principle helps predict:

  • Reaction mechanisms
  • Complex stability
  • Substitution patterns
  • Catalytic activity
  • Biological interactions

Advanced Topics

Additional considerations:

  • Global Hardness: Molecular stability
  • Local Hardness: Site reactivity
  • Fukui Functions: Reactivity indices
  • DFT Applications: Computational studies

Essential HSAB Formulas

Absolute Hardness

η = (IP - EA)/2

Absolute Softness

S = 1/2η

Electronegativity

χ = (IP + EA)/2