O” shifts

Gas FC outlet w/o shift. FC outlet w/o shift effect of shift rxn FC outlet in shift equil. FC outlet in shift equil. 

A linear relation (eq. (4.11)) permits prediction of thiocarbonyl shifts from the C = O shift values of the parent carbonyl compounds [330]. 

In the mass spectra of l-hydroxy-2-aryl-4-nitroimidazole-3-oxides the molecular ions and the fragments [M - O], [Ar-CH=NH], [Ar-CNH], [ArCN] were observed [355, 1300]. A careful mass spectrometric investigation of these oxides showed an unusual fragmentation. Along with an O-shift (with subsequent formation of 02) and the formation of the [Ar-C(0]+ the cation and other processes an unexpected release of N203 (or N20 + 02) from the molecular ion with formation of the [HC(CN(0)CHAr]+ fragment was noticed [1300],... 

Ln + induced water O shifts of [Ln(DOTA)] solutions show that the hydration number of the complexes is one across the lanthanide series [59]. The substantial pseudocontact contribution to its LIS indicated that this water ligand has a preferred location in the complex. Two sets of peaks have been observed in and NMR spectra of [Ln(DOTA)] complexes at room temperature showing the presence of two slowly interconverting structural isomers [60-63]. In the spectra of the paramagnetic complexes, one isomer has larger LIS values than the other. These structural features have been confirmed by luminescence studies [51, 64]. The temperature dependence of the and NMR spectral features of both the dia- and paramagnetic Ln + complexes indicates that the... 

In an attempt to find a new entry to unsymmetrical dialkoxydisul-fides, Braverman in 2004 prepared a munber of very unstable monoalkoxy chlorodisulfides 277 (Scheme 68) [154]. Although chlorides 277 turned out to be imsuitable for the initial goal, they underwent 1,4-additions to electron-rich diene 278 yielding 279 as primary adducts. These imderwent [2,3]-o-shifts producing thiosulfinates 280 as final products. 

Besides HF and TFA, the two extremes of acid treatment generally employed in the final deprotection step, alternative acids have been proposed, such as MsOH and TfOH, particularly in the context of arginine protection (Table 2). These acids, however, are known to generate serious side reactions such as aspartimide formationt and an N O shift at serine or threonine residues.Moreover, independent of the type of arylsulfonyl group employed, cations originating from the acid-mediated cleavage lead to alkylation and arylsulfonylation of reactive side chains, as present in tryptophan and tyrosine residues. Additionally, sulfation of hydroxy groups is even observed, as well as... 

The chemical shifts for CO2 and CHF3 are largely invariant with changes in pressure and temperature. For CO2 the C chemical shift is 6128, and the O shift 5 70. For CHF3 the proton resonance is a quartet at 5 7.5 (Vhf = 79.7 Hz). This could potentially obscure a significant region of H NMR spectra limiting its usefulness in that respect. The NMR resonance is a quartet at 5 111.7 ( /cF = 273.6 Hz). 

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