Additivity, inductive effects effective charge

Finally, the use of the effective charge density is helpful. It clearly shows that the response of the water to the presence of the ions closely mirrors the net ionic density suggesting that the response is quite local. In addition, this treatment for the polarizable models suggests the presence of an additional, weak effective charge layer due to the inductions in the surfactant just inside of the normal double layer. 

According to Roberts et al. the direction of addition of ammonia to 3-substituted benzynes might be predicted by considering the amide ion to add so as to provide the most favorable location of the negative charge with respect to the inductive effect of the orienting substituent. Thus, ammonia adds to 3-methoxybenzyne (39) producing chiefly n-aminoanisole (40). 

Fig. 2. Components of Li enthalpies of complexation with methylamines. Successive steps indicate the effect on energy of interaction between Li and the amine of inclusion of additional components of the binding energy. The diagram shows that the permanent dipoles on amines (the charge on the nitrogen of the isolated amine) favor ammonia over trimethylamine complexation, but that polarizability and inductive effects (shift of negative charge onto the nitrogen in the complex) cause a massive turnaround in favor of complexation with trimethylamine rather than ammonia. Of particular importance is the near inversion of order caused by the addition of repulsive van der Waals terms. Modified after Ref. (9).

Where the positive charge on the atom adjacent to the nucleus is real rather than formal, i.e. NR3 rather than N02, there is evidence that its effect on o complex stability is exerted through a field effect (cf. p. 22) operating through space, in addition to any polar (inductive) effect operating through the bonds. The deactivating effect of Y on the nucleus declines, i.e. the overall rate of substitution increases, in the approximate order ... 

Note that m-nitrophenol has pATa 8.4, and is a lot less acidic than o-nitrophenol or p-nitrophenol. We can draw no additional resonance structures here, and the nitro group cannot participate in further electron delocalization. The increased acidity compared with phenol can be ascribed to stabilization of resonance structures with the charge on a ring carbon through the nitro group s inductive effect. 

The vinyl halide product is then able to react with a further mole of HX, and the halide atom already present influences the orientation of addition in this step. The second halide adds to the carbon that already carries a halide. In the case of the second addition of HX to RC CH, we can see that we are now considering the relative stabilities of tertiary and primary carbocations. The halide s inductive effect actually destabilizes the tertiary carbocation. Nevertheless, this is outweighed by a favourable stabilization from the halide by overlap of lone pair electrons, helping to disperse the positive charge. 

This book is about atomic charges, chemical bonds, and bond energy additivity. However, nuclear magnetic resonance, inductive effects, zero-point and heat content energies, and other topics are an integral part of this study, to achieve... 

Nucleophilic addition readily takes place with pyridinium salts attack is normally easier at the C-2(6) position, since the inductive effect of the positively charged nitrogen atom is greatest here (Scheme 2.28). When the sites adjacent to the nitrogen are blocked, however, attack occurs at C-4. The products are dihydropyridines. 

CI,C is less basic than F,C . F can disperse charge only by an inductive effect [see Fig. 3-5( )j. In addition to an inductive effect. Cl uses its empty 3d orbitals to disperse charge by p-d tr bonding, see Fig. 3-5(fc). F is a second-period element with no 2d orbitals. 

The formal rt-electron density at each atom in an odd AH radical (e.g., 408) is unity, and to a first approximation it will be the same in isoelectronic radical cations (e.g., 409). Approximately (because inductive effects are neglected), a unit positive charge is localized on the heteroatom. Introduction of aa additional electron into these cations (e.g., 409) gives mesomeric betaines (e.g., 410). Because the electron enters a NBMO, it is restricted to... 

In addition to a relatively small inductive effect, two modes of stabilization of positive charge by the P-R3M substituent have been suggested. The first involves the classical cation 7, where the positive charge is stabilized by hyperconjugation (G-p conjugation) between the C-M o bonding orbital and the vacant carbocation... 

In addition to external factors such as solvent effects, there are internal factors that influence anionic stability. Among these are inductive effects (how do electron-donating or electron-withdrawing substituents affect a molecule ), and resonance effects (is the charge localized or delocalized ). As inductive effects generally work in concert with resonance effects, our primary focus will be on the resonance effects themselves. 

Alkyl groups are substituents with a positive induction effect which increases electron density in a series ortho- > meta > para-positions. The secondary effect of conjugation imparts an additional negative charge in the ortho- and para-positions. The resulting action of both of these effects is similar to that of a positive mesomeric effect. 

---