Hydrogen randomization Ions

For a number of specifically-labelled 1-methylimidazoles the early stages of the mass spectral fragmentation have been examined in some detail. The relative losses of labelled and unlabelled HCN from the and [M-lT species show that there is an insignificant amount of hydrogen-randomization in the molecular ions prior to fragmentation. Sub-... 

The relative losses of unlabeled vs. labeled HCN from the M and [M — 1] ions of a number of specifically labeled 1-methylimidazoles (and 1-methylpyrazoles) show that hydrogen randomization in the molecular ions prior to fragmentation is insignificant. The expulsion of HCN can follow two distinct pathways elimination involving positions 2 and 3 (predominant in 1-methylimidazole), and elimination involving N(l) and its attached methyl group (predominant in 1-methylpyrazole). The molecular... 

The cyclic voltammogram of Cu UPD on Au(lll) shows two well-defined pairs of current peaks A1/A2 and BxjBi corresponding to energetically different adsorption/desorption processes (Fig. 15) [320-322, 337]. In the first step (peak Ai), the transition between randomly adsorbed copper and (hydrogen) sulfate ions into an ordered layer of copper atoms (electrosorption valency y 1.8 [339, 340]) and coadsorbed sulfate ions takes place. The resulting ( 3 X 3)R30° structure was first observed by ex situ LEED and RHEED experiments [354], and later confirmed by in situ SXS [350], STM [341-343], and AFM [344]. QCM [352, 353], chrono-coulometric [339, 340], and FTIR-... 

Many synthetic water-soluble polymers are easily analyzed by GPC. These include polyacrylamide,130 sodium poly(styrenesulfonate),131 and poly (2-vinyl pyridine).132 An important issue in aqueous GPC of synthetic polymers is the effect of solvent conditions on hydrodynamic volume and therefore retention. Ion inclusion and ion exclusion effects may also be important. In one interesting case, samples of polyacrylamide in which the amide side chain was partially hydrolyzed to generate a random copolymer of acrylic acid and acrylamide exhibited pH-dependent GPC fractionation.130 At a pH so low that the side chain would be expected to be protonated, hydrolyzed samples eluted later than untreated samples, perhaps suggesting intramolecular hydrogen bonding. At neutral pH, the hydrolyzed samples eluted earlier than untreated samples, an effect that was ascribed to enlargement... 

---