Electron-withdrawing groups, effect acidity

In general, resonance effects lead to the same result as field effects. That is, here too, electron-withdrawing groups increase acidity and decrease basicity, and electron-donating groups act in the opposite manner. As a result of both resonance and field effects, charge dispersal leads to greater stability. 

Eclipsed conformation, 7, 254 Electrocyclic reactions, 341, 344-348 Electrol ic oxidation, 307 Electrolytic reduction, 307 Electromeric effect, 24 Electron configuration, 3 Electron density, 21, 26, 29, 393 Electron-donating groups, 23, 26 addition to 0=C and, 183 addition to 0=0 and, 205, 206 aromatic substitution and, 153, 158 pinacol change and, 115 Electronegativity, 21, 22, 95 Electrons, lone pair, 10, 72 Electron spin, paired, 2, 308 Electron-withdrawing groups, 23 acidity and, 59, 61, 62, 272... 

Electron-withdrawing groups increase acid strength electron-donating groups decrease acid strength, C. Inductive Effects on Acidity... 

The Cl— -CH2C00 ion is more stable than CHjCOO", so for chloroethanoic acid is much greater than that for ethanoic acid. Additional electron-withdrawing groups increase this effect, but the influence of the electron-withdrawing group on acid strength falls off with distance. 

Electron releasing substituents attached to the ring have a negligible effect on the acidity of phenols Strongly electron withdrawing groups increase the acidity The compound 4 nitro 3 (tnfluoromethyl)phenol for example is 10 000 times more acidic than phenol... 

Similarly, carboxylic acid and ester groups tend to direct chlorination to the / and v positions, because attack at the a position is electronically disfavored. The polar effect is attributed to the fact that the chlorine atom is an electrophilic species, and the relatively electron-poor carbon atom adjacent to an electron-withdrawing group is avoided. The effect of an electron-withdrawing substituent is to decrease the electron density at the potential radical site. Because the chlorine atom is highly reactive, the reaction would be expected to have a very early transition state, and this electrostatic effect predominates over the stabilizing substituent effect on the intermediate. The substituent effect dominates the kinetic selectivity of the reaction, and the relative stability of the radical intermediate has relatively little influence. 

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