Question:
If the Hammett equation constant ($\sigma$) is negative, it indicates:
If the Hammett equation constant ($\sigma$) is negative, it indicates:
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Negative $\sigma$ = Giving (Donating); Positive $\sigma$ = Pulling (Withdrawing).
Updated On: May 15, 2026
- Hydrophobic group
- Hydrophilic group
- Electron donating group
- Electron accepting group
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The Correct Option is C
Solution and Explanation
Step 1: Concept
The Hammett equation ($\log \frac{k}{k_0} = \sigma \rho$) relates reaction rates and equilibrium constants to the electronic properties of substituents.
Step 2: Meaning
The substituent constant ($\sigma$) measures the electron-withdrawing or electron-donating ability of a group relative to hydrogen.
Step 3: Analysis
Positive $\sigma$ values represent electron-withdrawing groups (EWG) that increase acidity. Negative $\sigma$ values represent electron-donating groups (EDG) that decrease acidity compared to the benzoic acid standard.
Step 4: Conclusion
Therefore, a negative constant specifically signifies an electron-donating group. Final Answer: (C)
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