Cation-dominant

Relative concentrntions of different glycine species as a function of pH. Between about pH 3 and 9, the zwitterion is the principal species it has its maximum concentration at pH 6. the isoelectric point Below pH 2. the cation dominates above pH 10. the anion is the principal species. 

Loss of ethylene and subsequent formation of the stable 3//-pyrrolinine cation dominates the mass spectrum of 2,3,4,5-tetrahydro-l//-l-benzazepine <75OMS(10)992). Biphenylene (m/e 152), acridinium cation (m/e 179) and fluorene cation (m/e 165) are the major fragments in the mass spectra of dibenz[T>,/]azepines (74CJRV101). 

C-H transformation of alkanes by SET is still a developing area of preparative organic chemistry. Generation of cr-radical cations from alkanes in solution requires strong oxidants, and is achieved by photochemical and electrochemical oxidation. Under these conditions even unstrained strained alkanes may be functionalized readily. The C-H substitution is selective if the hydrocarbon forms a radical cation with a definite structure and/or deprotonation from a certain C-H position of the radical cation dominates. Overoxidations are the most typical side reactions that lead to disubstituted alkanes. This can usually be avoided by running the reactions at low alkane conversions. 

An additional series of calculations has been carried out for the complexes of the tetrads with the metal ions. It has been concluded that the stability of such tetrads is controlled by the presence of metal ions. In this presentation, we demonstrate that such cations dominate the H-bonding patterns that govern the structures of the DNA bases polyads. 

As with the optical spectra the presence of a porphyrin radical cation dominates the MCD spectra of compound I of catalase [177] and horseradish peroxidase [29,177], These spectra are quite distinct from that shown in Fig. 8, but vary similar to each other. This suggests that their radical cations must have similar structures [10]. 

AT-(4-BrC6H4CH2)py) [Ni(a-tpdt)2] Alternated layers of anions and cations — Dominant F interactions Dominant AFM interactions PM down to 1.5 K 92... 

Turner et al. (1981) and Byrne et al. (1988). Turner et al. (1981) used a database of stability constants for more than 500 metal complexes to calculate the inorganic speciation for 58 trace elements in model seawater at pH 8.2, 25 °C, and 1 atm. Byrne et al. (1988) extended this work by considering the influence of temperature and pH on speciation. The free hydrated divalent cation dominates the dissolved inorganic speciation of Zn(II) and the first transition series metals Mn(II), Co(II), and Ni(II). Strongly hydrolyzed trace metals include Be(II), Al(III), Fe(III),... 

It can be seen for the [N(Tf)2] ionic liquids, that the hydrogen-bond acidity does indeed vary with cation with [BMIM]+ being the most acidic followed by [BMPYJ+ and finally [BMMIMJ+ in both studies. However, changing to more basic anions leads to a dramatic drop in the acidity measurements in the solvation study, whereas it has only a limited effect in the Kamlet-Taft experiment. That is, the solvation measurement is anion dominated, whereas the Kamlet-Taft measurement is cation dominated. 

The nature of the mobile ionic species was questionable for a long period of time. For passive Al, Verwey [47] assumed in 1935 that exclusive transport of Al-cations occurs in a fixed oxygen matrix. The idea of mobile cations dominated the oxide formation theories for the next 30 years. It seemed to be reasonable, as the volumes of cations are much smaller than -anions (e.g. by a factor of 20 for AP+), even if the experimental results indicated a combined transport. Marker experiments in the sixties proved cation-transference numbers in the range from 0.3 to 0.7 for many systems (Al, Be, Nb, Ta, Ti, V, W) coming closer to 0.5 with increasing current density, that is, cations and anions move in fact simultaneously (Table 1). This indicates that effects of charge distribution become more important than individual ion properties like size or polarizability [25]. Exceptions are the crystalline oxides on Hf and Zr, which are pure oxygen conductors. 

The EQCM has also been used to study redox-driven ion and solvent transfers in Prussian Blue-related materials, in which one or other of the iron species is replaced by another metal. These include ferric ruthenocyanide ( ruthenium purple ) [111], silver hexacyanoferrate [112], and nickel hexacyanoferrate [113, 114]. EQCM data for the latter case - the best characterized of this set-was shown to be consistent with a broadly electrolyte cation-dominated electroneutrality mechanism (as for the parent Prussian Blue material), but with some evidence for electrolyte anion participation, in the redox process. 

It is well known that changes in redox states of EAPs require movement of ions in order to maintain electroneutrality. Electrochemical neutralization of p-doped polymers can be anion-dominant (anions are expelled from the polymer film), cation-dominant (cations diffuse into the polymer film), or a combination of both anion and cation movements [14,15]. The dominant process varies from polymer to polymer and is strongly affected by ion and solvent choices as well as by electropolymerization conditions and film thickness [16]. Typically for p-doping polymers, anion transport dominates when the anion is small and highly mobile, but cation transport dominates when the anion is large and immobile [17-19]. For instance, redox processes in polypyrrole are anion-dominant in most cases, but when poly(styrenesulfonate) is chosen as the counterion, cation transport is the dominant process [20-23]. 

Another interesting aspect is the crossover between cation-dominated conductivity and proton-dominated conductivity that should occur with increasing water content for PEC. So far, only PEM with their intrinsically low concentration of residual counterions were identified as proton conductors. However, for strongly humidified stoichiometric PEC with nominally no residual counterions, a similarly dominating proton contribution to the conductivity can be expected. Such knowledge is relevant for potential applications of PEM either as proton or as Li" conductors, in particular... 

Fragmentation Alkene elimination to give hydroperoxide radical cations and hydroperoxide elimination to yield alkene radical cations (dominating if larger alkyl groups are present). Alkene elimination can be followed by loss of OH , resulting in products that formally correspond to those obtained by 0-0 cleavage, which probably is not a one-step process (see scheme). 

Fragmentation Loss of alkyl by fragmentation of the C-O bond with concomitant double H rearrangement to form the protonated sulfonic acid ion (m/z 97 for methanesulfonates), which then loses water. Loss of the alkoxyl residue (fragmentation of the S-O bond). Formation of an alkene ion from the sulfonate alkyl by a McLafferty-type rearrangement. In aryl esters, the phenoxy ion and the phenol radical cations dominate the spectrum. 

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