Anions shifts

No firm decision, between an anion diradical mechanism and a concerted S ->0 1,2-anionic shift, could be made from the available evidence106. Interestingly, the use of a stronger base such as ethylmagnesium bromide results in rearrangement to trans-1,2-diphenylcyclopropanesulfinic acid in highly stereoselective manner (equation 36)107. 

Specific adsorption of ions other than protons causes the pzc and the iep to shift along the pH scale (Stumm, 1992). Specifically adsorbed cations (anions) shift the titration curve and the point of zero proton condition at the surface (pznpc) to lower (higher) pH values, whereas the iep is moved to higher (lower) pH values. The shift of the iep of hematite to a lower pH by adsorbed EDTA and Cl" is shown in Figure 10.8. 

Upfield shifts, negative, downfield shifts positive. 5-Substituted tetrazolate anion shifts in DjO relative to external NH NOj have also been listed >(86MRC984>. Methyl sulfate salt in CDnOD. Some confusion on N-3 and N-4 shifts in early spectra has been corrected <92MRC558>. 

Isocyanate and isothiocyanate carbon nuclei resonate between 120 and 130 ppm [77a]. Isothiocyanate carbons are slightly deshielded relative to comparable isocyanates. Typical nitrile shift values (110-115 ppm) are characteristic of thiocyanates (rhodanides), while the carbon nuclei of rhodanide and cyanate anions shift to lower field due to significant contributions of heterocumulene-type resonance formulae. 

Another type of ionic species was proposed by Uelzmann (92). Uelzmann suggested that from trialkylaluminum and titanium tetrachloride, TiClg)+ and (R3A1C1) caused cationic initiation on the titanium followed by an anionic propagation on the aluminum ion. Bestian and co-workers (70) proposed similar cationic intermediates which propagate by anionic shifts. These steps are the opposite of the anionic initiation and cationic propagation proposed in this review for the butene-1 polymerization. 

The details of the cupric salt reaction with the palladium adduct are not clear. Exchange to form a cupric alkyl is one possibility or complex formation,"probably with chloride bridges between the palladium adduct and cupric chloride, may occur with subsequent anion shift from palladium to carbon or perhaps an Sn2 displacement of the complex metal group by an anion may occur. Rearrangements producing 1,3 and 1,4 substituted products from linear olefins have also been observed. For example, 1-butene produced several percent of 1,3- and 1,4-chloro acetates and diacetates under the reaction conditions used 16>. "Hydrido-palladium acetate or chloride" -complexes would seem to be likely intermediates in these arrangements. 

In addition to covalent species and carbenium ions, the equilibria may involve onium ions, which are formed by reaction of carbenium ions with noncharged nucleophiles [Eq. (46a)]. This decreases the carbenium ions lifetime, and therefore the time available for isomerization to more stable and less reactive carbenium ions via hydride and alkyl anion shifts [Eq. (46b)]. Decreasing the probability of rearrangements by decreasing the carbenium ions lifetime is especially useful because such rearrangements can not be prevented by decreasing the polymerization temperature. 

Similarly, isomerized carbenium ions are formed in polymerizations of a-methylstyrene derivatives by either a 1,3-intramolecular or bimolecular methide anion shift, or by reaction of carbenium ion with an exo-unsatu-rated oligomer [cf., Eq. (10)] [13]. 

NHs" " at 1620-1600cm , and C02 at 670cm (where y is stretching or valence vibration and d is deformation vibration). The complex with composition 2 1 can be formed as a result from the addition of a second acid molecule to an ion pair (in increased amine concentration). Characteristic absorption band of the carboxylate anion shifts to the lower values of the wave numbers (as compared to the complex with 1 1 composition). ... 

The effect of the ionic liquid concentration on the equilibrium was studied in more detail. Figure 17 clearly shows that the addition of ionic liquid, independent of the basicity of the anion, shifts the position of the equilibrium towards the starting material, contradicting earlier reports [174], While the deviation from linearity... 

The synthesis of this special type of metallo-silanol starts most efficiently with an appropriate silyl metal complex, such as Cp(OC)2Fe-SiMe2R (R = H, OMe). An anionic shift of the silyl group from the iron to the cyclopentadienyl unit can be induced with lithium diisopropylamide, leading to the metallates 21a,b. Methylation with methyl iodide produces the neutral methyl iron complexes (C5H4SiMe2R)(OC)2Fe-Me (R = H, OMe), which can be converted either, for R = H, by the Co2(CO)8 method, or, for R = OMe, by hydrolysis in the presence of acetic acid, into the corresponding silanol 22. 

Compound Experimental Ground state v(C=X) MLCT state v(C=X) Shift Av(CsX) Calculated Anion shift Av(C=X) References... 

Solutions in methanol Cation and anion shifts in the hydroxy proton resonance 131... 

If the electrolyte contains an ion specifically adsorbed, the intersection point of the ao = f (pH) curves shifts and no longer represents the PZC determined with indifferent , or non-specifically adsorbed ions. Specific adsorption of cations shifts the intersection towards lower pH anions shift it towards higher pH. For example,... 

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