Ion character-activity relationships

Ownby DR, Newman MC. Advances in quantitative ion character-activity relationships (QICARs) Using metal-ligand binding characteristics to predict metal toxicity. Quant Struct-Act Rel 2003 22 1-6. 

Quantitative ion character-activity relationships can be developed for a range of effects based on metal-ligand binding theory. 

In this respect, Quantitative Ion Character-Activity Relationships (QICARs) and Quantitative Cationic-Activity Relationships (QCARs) have recently been developed (Ownby and Newman 2003, Walker et al. 2003). More research efforts are needed in this field, however, in order to develop and validate appropriate models. 

The relationship between alkyl chain length and rates of dealkylation has been explored (9). 3-Methylcholanthrene repressed the dealkylation of DMN, DEN, and dipropylnitrosamine (DPN) by rat hepatic microsomes the degree of repression was inversely proportional to alkyl chain length. Phenobarbital pretreatment resulted in induction of DEN deethylase activity. The effect of 3-methylcholanthrene on DEN deethylase activity in this study contrasted with a previous study, discussed above (3J8). This may indicate multiple forms of DEN deethylase as observed for DMN demethylase. The carbonium ion character of electrophiles generated in these reactions was demonstrated by the isolation of rearranged alcohol in the microsomal metabolism of DPN (366). 

As the solvent is changed to include increasing proportions of methylene dichloride, the dielectric constant increases and so does the solvating power of the medium. The active centres therefore become solvated by the solvent in preference to monomer molecules i.e. jc 1 and 0. In this case the slow step becomes the collision and reaction of the active centre with a monomer molecule in solution as proposed by Pepper and Reilly [13]. Hamann et al. have also speculated further as to the nature of the active centre. NMR spectra showed no evidence for the presence of perchlorate esters this, though not conclusive, is somewhat disappointing for the proponents of pseudocationic propagation. They have also reexamined Pepper s data for fe2 as a function of the dielectric constant, e, of the solvent. Previously Pepper and Reilly [13] had speculated that the linear relationship between log k2 and the function (e — l)/(2e + 1) indicated that the active species was dipolar in character (ion pairs ). Hamann et al. applied the Laidler Eyring theory [70] of dielectric effects... 

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