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The inductive effect is the redistribution of electron density through a molecular framework associated with the electron-withdrawing or electron-releasing influence of substituents. It is usually discussed as polarization transmitted through sigma bonds, distinguished from resonance through conjugated orbitals.

For example, an electron-withdrawing substituent near a carboxylic acid can stabilize its conjugate base and increase acidity. The effect usually weakens with increasing bond distance. Separating an inductive effect from electrostatic field effects is a modeling convention, so a qualitative substituent label is not a universal numerical prediction for every solvent and molecular geometry.

The strong $1810\mathrm{c}{\mathrm{m}}^{-1}$ band is an acyl chloride carbonyl stretching vibration. Compared with an ester, donation from a chlorine lone pair into the carbonyl antibonding molecular orbital is relatively ineffective, while chlorine's inductive effect withdraws electron density. The resulting stronger effective carbonyl force constant places the absorption above an ordinary saturated ketone band. Bond polarity alone is not a universal quantitative frequency rule.