Inductive effects electron-donating

Inductive and resonance effects account for the directing effects of substituents as well as for their activating or deactivating effects. Take alkyl groups, for instance, which have an electron-donating inductive effect and are ortho and para directors. The results of toluene nitration are shown in Figure 16.13. 

The destabilising influence of the electron-donating inductive effect of alkyl groups is seen in the observed carbanion stability sequence ... 

We can appreciate that ionization of the carboxylie acid is affected by the electron-withdrawing inductive effect of the ammonium residue hence the increased acidity when compared with an alkanoic acid. Similarly, loss of a proton from the ammonium cation of the zwitterion is influenced by the electron-donating inductive effect from the carboxylate anion, which should make the amino group more basic than a typical amine. That this is not the case is thought to be a solvation effect (compare simple amines). 

Me, a typical alkyl group, has an electron-donating inductive effect and is base-strengthening. Basicity increases with the increase in the number of Me groups. 

The a-secondary IE of two deuteriums on the rate of base-catalyzed CD exchange of toluene, 3A ( PhC112D)/k(PhCD is 1.31, and the [3-secondary D IE on the rate of base-catalyzed a-C-D exchange of ethylbenzene, k(PhCHDCH3)//t(PhCHDCD3), is 1.11 0.03.58 Similarly, from the rates of base-catalyzed a-C-D exchange of tolucne-a,4-r/2, -a,2,4,6-c/4, and -a,2,3,4,5,6-d6 and with an assumption of linearity of IEs, the contributions of ortho, meta, and para deuteration lead to rate retardations of 2.4, 0.4, and 1.8%, respectively.59 These are all kinetic IEs, but to the extent that the transition state resembles closely the carbanion, or to the extent that the reverse reprotonation is encounter-controlled and independent of isotopic substitution, these kinetic IEs represent equilibrium IEs on acidity. The IEs were interpreted in terms of an electron-donating inductive effect of D relative to H. 

Increasing alkyl substitution stabilizes an alkene by an electron-donating inductive effect. 

Problem 18.12 Which substituents have an electron-withdrawing and which have an electron-donating inductive effect (a) CH3CH2CH2CH2- (b) Br- (c) CH3CH2O- ... 

Conclusion The CH3 group directs electrophilic attack ortho and para to itself because an electron-donating inductive effect stabilizes the carbocation intermediate. 

Primary (1 °), 2°, and 3° alkylamines are more basic than NH3 because of the electron-donating inductive effect of the R groups. 

Electron-donating inductive effect (Section 7.14A) An inductive effect in which an electropositive atom or polarizable group donates electron density through O bonds to another atom. 

Nitration of toluene might occur either ortho, meta, or para to the methyl group, giving the three carbocation intermediates shown in Figure 16.14. All three intermediates are resonance-stabilized, but the ortho and para intermediates are the most stabilized. For both ortho and para attack, but not for meta attack, a resonance form places the positive chai directly on the methyl-substituted carbon, where it is in a tertiary position and can best be stabilized by the electron-donating inductive effect of the methyl group. The ortho and para intermediates are thus lower in energy than the meta intermediate and therefore form faster. 

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