Factor 3—Induction

It is assumed that Cr(IV) reacts quickly with Mn(II) but slowly with iodide ion for otherwise the induction factors would not be as found. 

Westheimer has also reviewed the induced oxidations by the Cr(VI)-As(III) couple of iodide, bromide and manganous ions vide supra). The induction factor of 0.5 for Mn(II) implies an intermediate tetravalent chromium species however, the factor of 2 for iodide points to a pentavalent chromium intermediate. Both... 

The oxidation induces the oxidation of manganous ion to Mn02 with an induction factor (see p. 280) of 0.5 . The rate of reduction of Cr(VI) is reduced simultaneously to a maximum extent of 50... 

Both schemes accommodate the kinetics, the primary isotope effect and the induction factor, which indicates that Cr(IV) is the initial stage of reduction of the oxidant. RoCek s mechanism does not accord with the solvent isotope effect of 2.5 per proton, which has just the value to be expected for acid-catalysis, for the O-H bond cleavage should be subject to a primary isotope effect of about 7. The ester mechanism is not open to this criticim. 

The solvent isotope effect suggests that no O-H cleavage is involved in the slow step and the effect of O-methylation indicates that a cyclic complex is involved. The induction factor is probably obscured by the reaction of Mn(III) and Mn02 with pinacol itself. The typical glycol-cleavage mechanism advocated for oxidations by Pb(IV) and I(VII) (p. 349) may well operate, viz. 

Reaction (1) is called the primary, main, or inducing reaction, which brings about induced reaction (2). Substances A, I and Ac taking part in both reactions (1) and (2) are called actor, inductor, and acceptor, respectively. The extent of the induced change is conventionally expressed by the induction factor F , defined as the ratio of the equivalents of the induced reaction to those of the primary reaction. 

Coupled reactions occur when the primary reaction results in an intermediate which enables the acceptor to react too. The main characteristic of this reaction is that the value of the induction factor is small, not exceeding 2 even under most favourable conditions for the induced change. Plotting F-, against the ratio of the initial concentrations of acceptor and inductor results in a curve having a limiting value. 

Since Fj = Z[Ac< ]/Z[I ,j] the value of the induction factor depends on the rate ratio of competing reactions (5) and (6). Thus, on increasing the initial concentration ratio of Ac to I over any limit, the rate ratio increases to infinity. In this case the coupling intermediate Aj is entirely consumed in reaction (6) in the oxidation of Ac d, i-e- P == 0, and Fj reaches its limiting value. The limiting... 

Unfortunately, only few of the systems listed in Tables 1 and 2 have been studied in detail there are many where even the value of the induction factor is unknown. Therefore, we shall deal with systems whose mechanisms are clear to some degree. 

Considering the limiting values of the induction factor it may be postulated that in the case of iodide and bromide the induced oxidation is caused by chromium(V), whereas for induced oxidation of manganese(II) chromium(lV) is the coupling intermediate. Therefore, one has to assume that in the course of reaction between arsenic(ril) and chromium(VI) both chromium(V) and chromium(IV) intermediates are involved. The mechanism below, proposed by Westheimer seems to be in agreement with experiment. 

It was observed by Gopala Rao and Sastri that the reaction between hydro-quinone and chromic acid leads to the induced oxidation of oxalic acid, glycerol, lactic acid, glucose, citric acid, and malic acid. If the concentrations of the above acceptors are cen times that of that of the hydroquinone inductor, the values of F found are, respectively, 0.51,0.46,0.35,0.27 and 0.17. The numerical values of the induction factor do not permit us to discuss the nature of coupling intermediate. 

VARIATION OF INDUCTION FACTOR WITH VARYING ACIDITY AND IONIC STRENGTH FOR THE IR0N(1I)-ARSENIC(I1I)-PER0XYDISULPHATE SYSTEM... 

The stoichiometry of the induced reaction depends, as in the Fe(II)-S20 system, on the iron(II)/iron(III) ratio and on the pH. Therefore, it can be expected that under identical experimental conditions (actor, inductor, and hydrogen ion concentration) the induction factors for the two systems should be identical. The data obtained show that this expectation is fulfilled. For the photo-induced oxidation of arsenic(III) the value of ks /k -j was found to be 2, while in the present system k Jk -j = 4. (Comparing these values with the value of k jk = 21, it can be concluded that the SO4 radical, formed by reaction (43), is not removed by the reaction... 

Various induction factors (often unknown) The same oncofoetal antigen can be expressed by a... 

Neither Cr(VI) nor Fe(III) can oxidize iodide ions rapidly. However a mixture of Cr(VI) and Fe(II) forms iodine rapidly from iodide ions. The oxidation of I is said to be induced by the Fe(II) — Cr(VI) reaction. At high [I ]/[Fe ] ratios, the induction factor (ratio of H oxidized per Fe + oxidized) is 2.0. Interpret this behavior, detailing the intermediates involved. 

As stated in the footnote on p. 5, phosphonium compounds afford a better example of chemical shifts which are essentially governed by inductive factors thus giving better correlations. 

The relation of Mnn oxidised to Asm oxidised is known as the induction factor, and is found to be about 0-5 at the beginning of the reaction, whatever amount of manganous salt may be present but the value diminishes as the action proceeds, for as the chromate concentration falls, the tervalent manganese is reduced by the tervalent arsenic to an increasing extent. The presence of a trace of potassium iodate produces great irregularity in the induction factor and lowers its initial value to about 0-25. 

Non genotoxic (-1) if, at all exposure times, no more than one effluent concentration indicated a light induction factor greater than 2. 

Genotoxic (+1) if, for at least one exposure time, there are at least 3 effluent concentrations where the light induction factor is greater than 3. 

The induction factor is defined as the ratio of the treated batch luminescence to the average luminescence of controls. 

Two alternative methods are used to interpret test results 1) the lowest effective concentration or 2) the induction factor. The lowest effective concentration is the lowest at which the median number of micronucleated erythrocytes is significantly different from that of control animals. IF (induction factor) is the ratio between the treated group median and that of controls. In some cases, such parameters were not applicable and a qualitative assessment was employed. 

IF Induction factors for any of the previous concentrations calculated as follows ... 

IC50 50% effect inhibitory concentration IF Induction factor... 

As follows from equations (2.16) and (2.17), it is not obligatory to operate the amount of expended inducer in the calculations. Moreover, there are conjugated processes that proceed without inducer participation. Therefore, it is of much greater importance to account for the expenditure of compound A in both reactions and to determine the induction factor via it. From these positions, equation (2.17) is somehow universal, because it reflects chemical induction in any display. Moreover, it is shown below, how many important consequences follow from it, which may not be deduced from equation (1.3). 

This means that the primary reaction mostly proceeds in the system. Hence, the higher the rate of this reaction, the lower is the induction factor (I) which approaches zero in the limit. Obviously, acceptor expenditure is low under these conditions. 

In fact, in the latter case, the catalyst (injected into the system with initial reagents) only speeds up interaction between the IP of the primary reaction and the acceptor. Therefore, D < v and, consequently, chemical conjugation takes place. This means that no matter how the reaction between the acceptor and the IP is intensified by the catalyst, the induction factor (the determinant) may not exceed v. When analyzing conjugated catalytic reactions, it should be taken into account that the amount of acceptor involved in the reaction may be significantly increased by application of a catalyst in both conjugated reactions. 

Note also that this inequality is typical only of systems in which chemical conjugation occurs. The induction factor correctly describes the three-component system in which owing to the inducer action an IP is synthesized. This product is a reagent but not a catalyst. However, application of the expression (1.3) shaped equation for... 

Moreover, if the primary reaction is monomolecular, and chemical induction occurs in this system, the induction factor may not be determined from equation (1.3). This is demonstrated by the limited type of equation (1.3) application range even to conjugated reactions. 

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