Substitution shifts, halide

The 31P values for a series of o-dimethylamino-substituted benzyltriarylphosphonium halides (increasing upfield shift of P resonances with increasing electron density at... 

Z values are both temperature- and pressure-dependent. The CT absorption band of substituted pyridinium halides is shifted hypsochromically as the temperature of the solution is decreased [59]. Thus, Z values decrease with increasing temperature due to a lowering of the solute/solvent interactions at the higher temperature. Furthermore, it has been shown that the CT absorption band of l-ethyl-4-(methoxycarbonyl)-pyridinium iodide is shifted bathochromically for solutions in methanol and ethanol with increasing pressure (up to 1920 bar), while for other solvents such as acetone and A, A -dimethylformamide it is shifted hypsochromically [60]. Except for the lower alcohols, the bulk solvent polarity generally increases with pressure [60]. 

Electrochemical characterization of the complete series [RuX6-n(RCN)n]. (n = 0 -6, X = Cl or Br) has provided confirmation of the systematic correlation between stoichiometry and central ion reduction potential, previously noted for the [OsCl6 (py)nP (n = 0 - 4) system. A graph of successive E° values (Ru / and Ru / ) vs. the extent of halide ligation (6 - n) shows that, upon each substitution of halide by nitrile, both couples shift by approximately +0.6 volts. 

Isomerization of fluoroolefins by a shift of a double bond is catalyzed by halide 10ns [7] The presence of crown ether makes this reaction more efficient [74] Prolonged reaction time favors the rearranged product with an internal double bond (equations 3-5) Isomerization of perfluoro-l-pentene with cesium fluoride yields perfluoro-2-pentenes in a Z ratio of 1 6 [75] Antimony pentafluoride also causes isomenzation of olefins leading to more substituted products [76]... 

Symmetric allylsilanes and unsymmetric allylsilanes, in which the silyl substituent is at the less substituted end of the allyl fragment, are available from allyl halides and trimethylsilylmetal reagents13. 2-Chloro-l-cyclohexenes react with inversion of configuration and a 1,3-shift, with better results in the presence of coppcr(l) iodide14. 

Propargylic acetates, halides, and sulfonates usually react with a double-bond shift to give allenes.34 Some direct substitution product can be formed as well. A high ratio of allenic product is usually found with CH3Cu-LiBr-MgBrI, which is prepared by addition of methylmagnesium bromide to a 1 1 LiBr-Cul mixture.35... 

Isomerization of 1,3-dienes (12, 36).3 The 1,5-hydrogen shift in isomerization of 1,3-dienes catalyzed by (naphthalene)Cr(CO)3 (1) can be used for synthesis of aryl-substituted exocyclic alkenes, which are not readily available by coupling of aryl halides with exocyclic vinyl halides. 

Reaction between acetonitrile and the radical-cations of secondary alkyl halides is almost entirely S l in character. Both direct substitution and 1,2-hydride shift reactions occur and the products from a chiral alkyl halide such as 2-iodooctane, are almost totally racemised [25]. 

Allylic halides usually give both SN2 products and products of substitution with an allylic shift (SN2 products) although the mixed organocopper reagent RCu— BF3 is reported to give mainly the SN2 product.22 Allylic acetates undergo displacement with an allylic shift (SN2 mechanism).23 The allylic substitution process may involve initial... 

The principal components of the trityl cation in zeolite HY are <5 = 282 ppm and <5j = 55 ppm. It is instructive to tabulate all of the 13C principal component data measured for free carbenium ions in zeolites as well as for a few carbenium ions characterized in other solid acid media (Table III). The zeolitic species, in addition to the trityl cation (119), are the substituted cyclopentenyl cation 8 (102), the phenylindanyl cation 13, and the methylindanyl cation 12 (113). Values for the rert-butyl cation 2 and methylcyclopentyl cation 17 (prepared on metal halides) (43, 45) are included for comparison. Note that the ordering of isotropic chemical shifts is reasonably consistent with one s intuition from resonance structures i.e., the more delocalized the positive charge, the smaller the isotropic shift. This effect is even more apparent in the magnitudes of the CSA. Since... 

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