Inductive effects origin

The reduction of the C— Br and C—1 group moments from 1.10 and 0.90 in bromo- and iodo-benzene to about 0.80 and 0.50 in 2-bromo- and 2-iodo-thiophene has been ascribed to the larger weight of resonance forms such as (8) and (9) in the thiophene series. The chlorine, nuclear, quadrupole, resonance frequencies of chloro-substituted thiophenes are much higher than those of the corresponding benzene derivatives. This has been ascribed to a relayed inductive effect originating in the polarity of the C—S o-bond in thiophenes. The refractive indices, densities, and surface tension of thiophene, alkyl- and halo-thiophenes, and of some other derivatives have been... 

The chlorine, nuclear, quadrupole, resonance frequencies of chloro-substituted thiophenes are much higher than those of the corresponding benzene derivatives. This has been ascribed to a relayed inductive effect originating in the polarity of the C—S a-bond in thiophenes. ... 

Originally the constant for the field/inductive effect was called the inductive constant ((jj). The field (through-space) contribution is, however, clearly larger than the inductive effect proper, i. e., the through-bond contribution. 

All the pectin lyases so far described are of fungal origin and are secreted extracellularly. Production of pectin lyase by Rhizoctonia solani, Botrytis cinerea, and Fusarium oxysporum f. lycopersici was induced by pectate with D-glucose,265 pectin showing a lower inductive effect.231... 

In his 1933 paper on "tautomerism," Ingold began discussion with references to the physics of the electron, citing a 1923 paper by J. J. Thomson and a recent book by John H. Van Vleck.62 He noted Lewis s contributions (1923) to the notion of inductive effect ( ) in which electrons remain bound by their original atomic nuclei Lowry (1923) to the notion of electromeric effect, in which there is a displacement of a duplet, shifting from one pair of atoms to... 

The KIE in the 2,6-dimethylpyridine-methyl iodide reaction is more than twice the KIE in the 2-methylpyridine-methyl iodide reaction. This is also consistent with a steric origin for the KIE because the 2,6-dimethylpyridine transition state must be much more sterically crowded than the 2-methyl-pyridine transition state. If the increase had been due to an inductive effect, the increase in the KIE in the 2,6-dimethylpyridine reaction should have been approximately twice the KIE for the 2-methylpyridine reaction, i.e. approximately 0.94 rather than the 0.91 that was observed. 

This transmission of polarity through the a bonds is termed an inductive effect. It is relatively short range, decreasing rapidly as the original dipole is located further away. It becomes unimportant after about the third carbon atom. However, the effects will increase with the number of polar groups, so we see increasing polarization effects with 1,1-dichloroethane and 1,1,1-trichloroethane. We shall often need to consider inductive effects when attempting to predict chemical reactivity. 

The original investigators noted that the preferred mode of cleavage for 5-endo-acetoxynorbornene is opposite to that predicted by the inductive effect consideration. 

M. J. S. Dewar [auxiliary inductive effect lies in the ionic character of the a bond between the heteroatom and its adjacent carbon atom. 

The calculated IEs ignore anharmonicity. Therefore, the ability of these calculations to reflect IEs discredits an inductive origin that requires anharmonicity. The calculations on carboxylic acids and phenols do overestimate the IEs, as shown in Fig. 3, but only an underestimate would be support for an inductive effect. The overestimation is likely to be due, at least in part, to the neglect of solvation, which stabilizes the anion and reduces the n-[Pg.164]

In 1954 Sandorfyand Daudel15) published their C" approximation, a one-electron approximation which employs a linear combination of sp3 orbitals and borrows most of its simplifying features from the Htickel theory. The originality of this method lies essentially in the introduction of a resonance integral m/J between sp3 orbitals of the same carbon atom. Sandorfy 16> showed that the inductive effect due to a heteroatom can be reproduced by such a calculation. 

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