Classical inductive effect

An inductive effect which involves the successive polarization of the bonds between X and Y. The decrease in the effect with increasing number of bonds is due to a falloff factor /, which decreases the effect for each successive polarization. The value of / is 0.33-0.36 . This is the classical inductive effect (CIE) model. 

When the conditions under which the reactivity or property that is measured are held constant and L is chosen as the measure of the extent of electrical-effect transmission, the classical inductive effect is given by equation 24 ... 

It has long been known that a substituent X in an XGY system can exert an electrical effect on an active site Y. It is also well known that the electrical effect which results when X is bonded to an sp hybridized carbon atom differs from that observed when X is bonded to an sp or an sp hybridized carbon atom. As electron delocalization is minimal, in the first case, it has been chosen as the reference system. The electrical effect observed in systems of this type is a universal electrical effect which occurs in all systems. In the second type of system, a second effect (resonance effect) occurs due to delocalization, which is dependent both on the inherent capacity for delocalization and on the electronic demand of file active site. In systems of the second type the overall (total) electrical effect is assumed to be a combination of the universal and the delocalized electrical effects. For many years an argument has sometimes raged (and at other times whimpered) concerning the mode of transmission of the universal electrical effect. Two models were proposed originally by Derick, a through bond model (the inductive effect) and a through space model (the field effect). These proposals were developed into the classical inductive effect (CIE) and the classical field effect (CFE)" models. As the CIE model could not account... 

In addition to the static induction effects included in I/scf, the hot Drude oscillators give rise to a 1/r6, temperature-dependent, attractive term. This jkg Ta2/r6 term is the classical thermodynamic equivalent of the London quantum dispersive attraction IEa2/r6. It corresponds to a small perturbation to the London forces, because k T is at least two orders of magnitude smaller than the typical ionization energy IE. The smaller the temperature of the Drude motion, the closer the effective potential is to the SCF potential, making Eq. (9-57) independent of mo, the mass of the oscillators. 

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 the water trimer induction nonadditivity provides a dominant contribution, which effectively overshadows all the other terms. Its mechanism is simple. For instance, in a cyclic water trimer the multipoles of A inductively alter the multipoles at B, which, in turn, inductively alter the multipoles at C, which then alter those on A, and so on, until the self-consistency is reached. Various formulations of this simple model were implemented in the simulations since the 1970s [84-87,63,64,50]. To include the many-body induction effects of point charges interacting with a set of polarizable atomic centers the following classical electrostatics equation is solved iteratively... 

The effect of fluorine substitution on phenol acidities was examined in detaiP . Through a charge analysis, the F-effect could classically be explained by invoking both resonance and induction effects. In the meta position, the halogen tends to stabihze preferentially the phenolate anion due to the resouauce effects, resulting in a smaller... 

For meta- and para-substituted phenols, log values spread over 2 log units from 3-dimethylaminophenol to 4-nitro-3-trifluoromethylphenol. Their order is well explained by classical electronic effects. A dual-substituent parameter analysis gives equations 16 and 17, where crp and ctr are the Taft field-inductive and resonance substituent constants, respectively. 

The empirical intermolecular force fields are in most cases built of terms that are in a close correspondence with the interaction energy components described above. One may say that such force fields are simplest possible implementations of the SAPT approach. The functional forms used are based on SAPT analysis of the asymptotic behavior of the components. The electrostatic interactions are usually approximated by interactions of fractional charges located on atoms in each monomer. In simplest cases, the induction effects are not included explicitly but some more sophisticated force fields use the classical polarization model. The dispersion forces are accounted for by hnear combinations of l/R ab terms where R b are interatomic distances and the exchange forces by either exponential or 1 terms. 

Kinetics of reacting I R = H, OMe with nucleophiles such as the enol of pentan-2,4-dione aromatic amines , phosphorus derivatives and some reactive aromatic compounds , and relative rates with substituted (cyclohexadienyl)Fe(GO)3 cation have been examined. These behave as classically expected, but in contrast to 1-or 2-OMe, a 3-OMe increases rate through its inductive effect. The kinetics agree with electrophilic substitution with the possible intermediacy of n complexes " . Because aryl (N-diene)Fe(CO)3 complexes can rearrange by dissociation into C-aryl derivatives", intermediates could also involve reaction with an N of an indole or a MeO (oxonium cation) of MeO-aromatics. 

The inductive model assumes that substituent effects are propagated by the successive polarization of the bonds between the substituent and the reaction site. This effect is transmitted through both the a bond network (a inductive effect) and the Jt-bond network (jt inductive effect).10 The field effect model assumes that the polar effect originates in bond dipole moments and is propagated according to the classical laws of electrostatics. The appropriate description of this effect is the Kirkwood-Westheimer model, in which the molecule is treated as a cavity of low dielectric constant submerged in a solvent continuum. 

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