1. What is pKa Prediction?

The pKa value represents the acidity or basicity of a compound in solution. This calculator predicts pKa from molecular structure and functional group characteristics, providing valuable information for drug design and chemical research.

2. How Does the Calculator Work?

The calculator uses the pKa prediction equation:

Where:

• \( \text{Structure Factor} \) — Molecular structure descriptor (dimensionless)
• \( \text{Function Factor} \) — Functional group descriptor (dimensionless)
• \( a, b, c \) — Empirical coefficients that vary by compound type

Explanation: The equation accounts for both structural and functional contributions to acidity/basicity, with different coefficients for acids and bases.

3. Importance of pKa Calculation

Details: Accurate pKa prediction is crucial for understanding drug solubility, membrane permeability, protein binding, and formulation stability in pharmaceutical development.

4. Using the Calculator

Tips: Enter structure and function factors (typically between 0-10), select compound type (acid or base). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the accuracy of this prediction?
A: Typical accuracy is ±0.5 pKa units for most organic compounds, though accuracy may vary for complex molecules.

Q2: What are typical pKa ranges?
A: For acids: 2-12, for bases: 5-12. Extremes outside these ranges are possible but less common.

Q3: How are structure and function factors determined?
A: These are calculated from molecular descriptors like Hammett constants, inductive effects, and resonance contributions.

Q4: Are there limitations to this equation?
A: Less accurate for polyprotic compounds, metal complexes, and molecules with strong intramolecular interactions.

Q5: Can this be used for drug design?
A: Yes, pKa prediction is essential for optimizing drug absorption and distribution properties.