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Quinoline is less basic than pyridine, even though it has more resonating structures. Why? Does the negative inductive effect reduce basicity of quinoline?

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This is not due to the inductive effect, but rather, due to solvation. The positive charge of quinoline on the nitrogen is harder to solvate due to steric repulsion of the nearby ring, whereas in pyridine, the small hydrogen atoms in place do not pose a strong steric hindrance for the solvation of the ion.

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  • $\begingroup$ The neighbour benzene also have a -I effect on Nitrogen how? $\endgroup$ – user60369 Mar 15 '18 at 11:02
  • $\begingroup$ @user60369 It can withdraw electrons through resonance (though wouldn't this be the reason for stabilizing the conjugated acid too?). Actually, in the gas phase, quinoline is predicted to be more basic than pyridine, so this is not the reason you're looking for. $\endgroup$ – ralk912 Mar 15 '18 at 14:55

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