8.17 
Electron withdrawal stabilizes the base by decreasing the electron density on the oxygen. Daarmee versterkt hij zijn geconjugeerde zuur.
Electron donation destabilizes the base by increasing the electron density on the oxygen. Daarmee verzwakt hij zijn geconjugeerde zuur.

The more deactivating the substituent, the more it increases the acidity of a COOH, an OH or an +NH3 group attached to a benzene ring.
The more activating the substituent, the more it decreases the acidity of a COOH, an OH or an +NH3 group attached to a benzen ring.