Transition range redox indicator

Used as redox indicator (transition range 1.08-1.12 V). Blue cryst. powder. Sol. H2O, EtOH, Me2CO insol. CCI4. E° + 1.10 V. 

A selected list of redox indicators will be found in Table 8.26. A redox indicator should be selected so that its if" is approximately equal to the electrode potential at the equivalent point, or so that the color change will occur at an appropriate part of the titration curve. If n is the number of electrons involved in the transition from the reduced to the oxidized form of the indicator, the range in which the color change occurs is approximately given by if" 0.06/n volt (V) for a two-color indicator whose forms are equally intensely colored. Since hydrogen ions are involved in the redox equilibria of many indicators, it must be recognized that the color change interval of such an indicator will vary with pH. 

If/ — 1, the range of values of E over which a colour change is observed is 0.118 volt and is shifted by 0.059 volt for each unit change in pH. Efn is often known as the transition potential for the indicator. A representative list of redox indicators is given in table 5.5. ... 

Table 19-3 lists transition potentials for several redox indicators. Note that indicators functioning in any desired potential range up to about +1.25 V are available. Structures for and reactions of a few of the indicators listed in the table are considered in the paragraphs that follow. 

So, redox indicators will have a transition range over a certain potential, and this transition range must fall within the steep equivalence point break of the titration curve. The redox indicator reaction must be rapid, and to use terms of the electrochemist, it must be reversible.Jf the reaction is slow or is irreversible (slow rate of electron transfer), the color change will be gradual and a sharp end point will not be detected. 

The strong signals in the amide I and II range (aroxmd 1,660 and 11,550 cm ) indicate the response of the protein scaffold to the redox transitions. The small bands at 1,734 cm / 1,746 cm have been assigned to a glutamic acid side chain (Glu 278) and represents the proton coupling to electron transfer. 

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