Aliphatic systems

The reaction parameter p depends upon the reaction series but not upon the substituents employed. Values of the reaction parameter for some aromatic and aliphatic systems are given in Tables 9.2 and 9.3. 

Since substituent effects in aliphatic systems and in meta positions in aromatic systems are essentially inductive in character, cr and cr values are often related by the expression cr = 0.217cr — 0.106. Substituent effects fall off with increasing distance from the reaction center generally a factor of 0.36 corresponds to the interposition of a —CHj— group, which enables cr values to be estimated for R—CHj— groups not otherwise available. 

Olefin synthesis Irom phosphorane ylides (e g 3) with aldehydes or ketones cis olelins predominate in aliphatic systems trans m coniugated olefins... 

Modern concepts have been extended to the chemistry of heterocyclic compounds more slowly than to the chemistry of aromatic and aliphatic systems, but efforts are now being made to classify and explain the properties and reactions of heterocyclic compounds in terms of these newer ideas (cf. reference 11). However, many of the most important heterocyclic compounds are potentially tautomeric, and elucidation of their tautomeric composition must precede a logical treatment of their properties. Further, many natural products such as the nucleic acids and alkaloids contain potentially tautomeric groups and information of this type is needed for a detailed explanation of th reactions which they undergo,... 

The nature of the substituent group X plays an important role in determining the relative stability of the various tautomeric forms. In aliphatic systems the tendency of C—XH to become CH— C 1=X increases markedly in the order X = CHz < NH < O, and certainly hydroxy compounds show less inclination to exist as such than do amino compounds. The position of S in this series is not completely... 

In normal carbonium-ion chemistry, reaction proceeds from a precursor with a tetrahedral carbon capable of asymmetry hence, the stereochemistry of displacement in an aliphatic system can be ascertained by observation of the fate of the chiral center from reactant to product. An ethylenic system, of course, has no such chiral center, and hence there can be no change in optical configuration as the reaction proceeds. However, the stereochemistry of vinylic displacement and hence the symmetry and geometry of the intermediate can be... 

The network from system 3 is distinct from the rest, being a glass at room temperature and also having a rubbery shear modulus near the value expected on the basis of G°. Possible reasons for this high value of G/G° follow those discussed previously with reference to Mc/Mc and Figure 9. The more flexible chains of the aliphatic systems give lower values of Tg, resulting in elastomers at room temperature. 

Chain processes, free radical, in aliphatic systems involving an electron transfer reaction, 23,271 Charge density-NMR chemical shift correlation in organic ions, 11,125 Chemically induced dynamic nuclear spin polarization and its applications, 10, 53 Chemiluminescence of organic compounds, 18,187... 

Electron-transfer reaction, free radical chain processes in aliphatic systems involving an, 23, 271 Electron-transfer reactions, in organic chemistry, 18,79 Electronically excited molecules, structure of, 1, 365... 

Force-field methods, calculation of molecular structure and energy by, 13,1 Free radical chain processes in aliphatic systems involving an electron-transfer reaction, 23, 271 Free radicals, and their reactions at low temperature using a rotating cryostat, study of, 8. I Free radicals, identification by electron spin resonance, 1, 284... 

In the second edition of his book33 Stewart proposed a parallel between the rate of esterification of 2-substituted benzoic acids and the molecular weights of the substituents, the nitro group strongly deviating from this relationship. The first actual attempt to define a set of steric parameters is due to Kindler39. It was unsuccessful these parameters were later shown to be a function of electrical effects. The first successful parametrization of the steric effect is due to Taft40, who defined the steric parameter Es for aliphatic systems by the expression ... 

Although these approaches to aromatic C-P bond formation resemble in some ways reactions useful for C-P bond formation in aliphatic systems, clearly there are structural/electronic restrictions and differences in mechanisms. Other approaches to aromatic C-P bond formation are of greater generality and usually more efficient. 

Chain processes, free radical, in aliphatic systems involving an electron transfer reaction,... 

Electron-transfer reaction, free radical chain processes in aliphatic systems involving an, 23, 271... 

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