Cations structural effects

These structural effects are also found by MO calculations. Calculations at die MP4/6-311++G level have been performed on the ally cation and indicate a rotation barrier of 36-38 kcal /mol. ... 

Any structural effect which reduces the electron deficiency at the tricoordinate carbon will have flie effect of stabilizing the caibocation. Allyl cations are stabilized by delocalization involving the adjacent double bond. 

Macropolycyclic ligands, 2,942 classification, 2,917 metal complexes binding sites, 2, 922 cavity size, 2,924 chirality, 2, 924 conformation, 2,923 dimensionality, 2, 924 electronic effects, 2, 922 shaping groups, 2,923 structural effects, 2,922 molecular cation complexes, 2,947 molecular neutral complexes, 2,952 multidentate, 2,915-953 nomenclature, 2,920 Macro tetrolide actins metal complexes, 2,973 Macrotricycles anionic complexes, 2,951 cylindrical... 

A unimolecular ionization was shown to be the mechanism of solvolysis by means of rate studies, solvent effects, salt effects, and structural effects (179,180). The products of reaction consist of benzo [bjthiophen derivatives 209 or nucleophilic substitution products 210, depending upon the solvent system employed. By means of a series of elegant studies, Modena and co-workers have shown that the intermediate ion 208 can have either the open vinyl cation structure 208a or the cyclic thiirenium ion 208b, depending... 

In order to imderstand the effects of the cation structure in the transesterification between methanol and EC, quaternary ammonium chloride catalysts of different alkyl cations such as TPAC, TBAC, THAC, TOAC, and TDodAC were used at 140 C. Table 1 shows EC conversions after 1 h... 

This kind of an rap2- -racr interaction may lead to a marked bond lengths alternation the extreme structural effect of such an interaction is certainly found for S7, but also other neutral and cationic polychalcogen compounds frequently exhibit this interaction. 

Allenyl cations 1 are a stabilized form of vinyl cations1-3 in which the /1-carbon atom of the vinylic structure is part of the substituent which effects the stabilization of the ion via its electron-donating ability. This leads to a resonance hybrid having formally the alkynyl cation structure 2. Allenyl cations should be distinguished from the allenyl substituted carbenium ions 3 formulated as the mesomeric structures of the vinyl cations 4 (dienyl cations) stabilized by an w-vinyl group (equation 1). 

N-Alkylhydroxamic acid hydrolysis Methyl Violet + OH" Cl C12H25S03Na + H30+, CTABr + OH". An attempt made to separate electronic and hydrophobic effects on the micellar reaction Anionic and cationic micelles. Effect of surfactant structure examined Berndt el at., 1984 Malaviya and Katiyar, 1984... 

Effect of cation structure on the kinetic stability of RNH,PF6 complexes of [28] in CDClj" 1 ... 

Exploitation of the cationic/hydrophobic effect for mucosal substrate use is a design principle that lends itself toward the investigation of a variety of structural analogues. However, the measure of success for any vehicle, combination of activities, and a final formulated product will be the demonstration of unequivocal efficacy in vivo. 

For an explicit examination of the basis set superposition error on weakly bound cationic structures at various theoretical levels, we performed full counterpoise calculations as outlined in Section IIB (Table 5). Table 5 demonstrates nicely that the magnitude of the BSSE is indirectly proportional to the size of the basis set at TZ2P, the error is on the average only about a quarter of that at DZP. This effect becomes more apparent with increased incorporation of electron correlation. At our best theoretical level, the BSSE amounts to only 0.1 kcal mol" (Table 5), which is insignificant for the dissociation energy of about 1.5 kcal mol". ... 

The most comprehensive study of lithium cation basicities for organic bases was conducted by Taft, Gal and coworkers who investigated the effect of molecular structure on the gas-phase cation and proton basicities. Taft s LCA scale was revised and extended, and the lithium cation basicity scale now includes over 200 compounds. In the same work the correlations between gas-phase basicities toward lithium cation (LCB) and proton (GB) were examined. Good correlations are obtained provided that separate lines are drawn for homogeneous families and the differences in slopes are traced back to the different sensitivities to structural effects. Large deviations are explained by either a different attachment center for Li+ and H+ or a chelation effect toward Li+. Figure 5 describes three types of interactions that involve chelation of a lithium cation. 

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