Functional groups inductive electron-donating

Tab. 5.3 Inductive and Resonance Substituent Effects of Various Functional Groups Electron donation...

Alkyl groups are weak inductive donators and at the smallest shift we have the groups that, on balance, donate elections to the ring and increase the shielding at the carbon atoms. Amino is the best of thesje. So a nitrogen-based functional group (NO2) is the best electron withdrawer while another (NH2) is the best electron donor. 

Enthalpies of formation have been measured for BF3 adducts of a number of carbonyl compounds PhCOX. The electron-donating strength of the oxygen atom is directly related to the inductive effect of the group X, although the establishment of a basicity scale for the carbonyl function must also take into account steric effects.214 The following order was found for the basicities benzaldehyde = acetophenone > hindered ketones > benzoic esters a-chloroacetophenone > benzyl chloride. 

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