Reversibility cation

The.effect of the entropy of activation was noted above for the quaternary pyridine salts (280 and 281). In future work, it may also be found to reflect the electrostatic or hydrogen-bonding interactions in transition states of amination reactions and the effect of reversible cationization of an azine-nitrogen. Brower et observed a substantial rate difference between piperidino-dechlorinations of 2-chloropyrimidine in petroleum ether and in alcohol due partly to the higher entropy of activation in the latter solvent (Table III, lines 3 and 4). 

L Leaking, NT Non-Transparent, PC Partially Collapsed, R Reversed (Cation Interior), S Sticky, ST Semi-Transparent, SiM Stable in Media, S S Smooth and Swollen, T Transparent... 

My last kinetic work was aimed at determining the kp+ of a range of monomers by what I believed to be a reliable method. For kinetic and electrochemical reasons I chose nitrobenzene as the solvent, and I chose carbenium and carboxonium salts as initiators so as to achieve a clean and fast initiation. The rate-constants were adequately reproducible, but it turned out that they were not the kp+. The project was flawed because I had been unaware of the reversible cationation of the solvent by the carbenium ions. A careful analysis of the kinetic, analytical and thermochemical results gave a new insight into the reaction mechanisms in nitrobenzene, but the main objective had eluded me. 

CAS-1 is the first microporous calcosilicate zeolite-like crystal material and can be easily synthesized with or without organics. The reversible cation-exchangeability and the selectively adsorptive properties of CAS-1 are analogous to those for zeolites and molecular sieves. CAS-1 can withstand high temperature calcination indicating that it has a good thermal stability that is common for zeolites. 

Ghoussoub A, Lehn J — M, Dynamic sol-gel interconversion by reversible cation binding and release in G-quartet-based supramolecular polymers. Chem. Commun. 2005 (46) 5763-5765. 

Complexing with metal ions or acylation with organic or inorganic reagents produces reversible cationization of azines. The formation of metal ion complexes may facilitate reactions, as in the amination of... 

The phenomenon of ion exchange is thought to be the oldest physical process known to man, dating back to descriptions in the Bible and the writings of Aristotle. It was also the first property of zeolites to be studied scientifically when, in 1858, Iiichom [1] showed that the natural zeolites chabazite and natrolite were capable of reversible cation exchange. 

Because of their reversibility, cation exchange reactions can be driven forward or reverse by manipulating the relative concentrations of reactants and products. In the laboratory, common techniques for driving the reactions toward completion are to use high (> 1 M) concentrations of exchanging cations and to maintain low concentrations of product cations by leaching or repeated washings ... 

Different amphipathic helical peptides can be membrane-stabilizing or lytic to membranes depending on the structure of the helix, i ich in turn determines the nature of its association with the membrane. Features of peptides that are responsible for their specific properties have been discussed [22]. The type of peptide is of importance for the functioning of the cells. It has been shown that a mixture of anionic amphiphilic peptides with charge-reversed cationic peptides did induce a rapid and efficient fusion of egg phosphatidylcholine vesicles, but no fusion was observed with each peptide alone. 

The reverse cation-anion transformation is also feasible and involves the endcapping of the carbenium ion with a species capable of further reaction with an alkyllithium. 

A theoretical study of a thiophene/furan copolymer shows that with increasing percentage of thiophene and with increasing block sizes for a given composition the dopability of the copolymer by electron acceptors and donors (p- and n-type doping) is increased [252]. Poly(isothianaphthene) (PITN) can be reversibly cation- and anion-doped (BU4NBF4) without decomposition of the material... 

Poly(isothianaphthene) (PITN) can be reversibly cation- and anion-doped without decomposition of the material. PITN with these two reversible and stable redox states of different colors is a potential candidate for electrochromic displays. The reversible redox reaction of PITN and the existence of a relatively stable residual charge can be used in electronic devices, such as memories with learning effect (reading-writing device) [253]. 

By combining an electrically conductive polymer (e.g. POT) prepared by spin coating from solution with a solid polymer electrolyte and a metal oxide, a sohd state electrochromic device is constructed [713]. Substrates coated with PT can be used in electrochromic displays, in solar cells (cf Sect. 6.3), and for corrosion protection [714]. Poly(3,4-ethylenedioxythiophene-2,5-diyl), which has good electrochromic properties, (for structure cf Sect. 1.2) can used as an electrode in a solid state electrochromic cell (cf Sect. 3.4.3) [43]. PITN can be reversibly cation- and anion-doped without decomposition. This polymer, with... 

Fig. 3 Polyassociation of bis-guanine monomers (G-G) into a two-dimensional supramolecular polymeric array based on the formation of G-quartets, stabilized by potassium cations, and interconversion of the resulting hydrogel with the corresponding sol state through reversible cation binding and release by the [2.2.2] cryptand, modulated by acid-base alternation. The 2D array on the right is represented in an idealized fashion ignoring any defect...

Actually, anodic dissolution has long been regarded as a reversible process in the framework of the so-called metal-metal ion interfece [11,12]. Accordingly, the direct (metal oxidation and crystal dissolution) and the reverse (cation reduction and crystal growth) steps must proceed via the same routes even at the microscopic level [13,14]. This seems to be not always true even for systems mentioned as classical examples of equilibrium in textbooks [15]. The equilibrium point of view is a... 

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