Polarographic data

The structure of 5-amino-l-thia-2,4-diazoles has been clarified by Goerdeler, Huppertz, and Wember who compared the ultraviolet spectra and basicities of 194 (E, = Me or Ph) and the methylated derivatives 195 and 196, thereby showing that 194 exists in the amino form. This conclusion is supported by polarographic data. ... 

The reduction potentials, measured by scanning voltammetry, are substitution dependent.282 As shown in Table 12 for a series of triaryl tetrazoliums (169), the reduction becomes easier when electron-withdrawing substituents are present. This is in agreement with the polarographic data on a series of benzothiazolyl tetrazolium salts (170).283 With bis tetrazolium... 

The software required was based on a flow diagram of the program for digital control and a flow chart of the program for processing the polarographic data. 

Polarographic data indicates that the energy of o x decreases in the order... 

Oxidation-reduction potentials, polarographic data, etc. Marcus, Y. Kertes, A. S. Yamir, E., Compilers,... 

Electrochemical reduction of camphor-and norcamphoroxime at a Hg cathode proceeds with a high degree of stereoselectivity to give products of opposite stereochemistry to those formed in the dissolving metal (Na-alcohol) reduction of the oximes. The electrolyses are proposed to proceed by a kinetically controlled attack by the electrode on each oxime from the less hindered side (Fig. 62) [348]. In contrast, the corresponding N-phenyl imines yield products of the same stereochemistry as those isolated from a dissolving metal reduction. Cyclic voltammetry and polarographic data point to RH and intermediates in this case that are proto-nated from the least hindered side [349]. 

Values of A , and k may be extracted from the polarographic data, although the treatment is complex. Examples of its use to measure the rate constants for certain redox reactions are given in Refs. 339 and 340 which should be consulted for full experimental details. The values obtained are in reasonable agreement with those from stopped-flow and other methods. The technique has still not been used much to collect rate constants for homogenous reactions. The availability of ultramicroelectrodes has enabled cyclic voltammograms to be recorded at speeds as high as 10 Vs". Transients with very short lifetimes (< ps) and their reaction rates may be characterised. ... 

Even carefully purified acetonitrile and DMF still contain nucleophilic impurities, which can interfer with the electron transfer SEM/OX so strongly that it becomes irreversible and E2 cannot be derived from the polarographic data. With E2 s rather positive, as e.g. in 15, this behaviour is most pronounced. Probably the adduct of 15qx and nucleophiles e. g. 75 undergoes consecutive reactions like ring openings. In these cases addition of some perchloric acid trifluoroacetic acid or its anhydride and aluminium oxide will completely suppress such interfering... 

Batch, Dance and Holm have prepared a number of iron-bis-dithiolene chelates for which magnetic susceptibility measurements indicate spin exchange in dimeric units in the solid (79). In addition polarographic data strongly suggest that the dimeric units are retained in dichloromethane solution. Starting with the neutral complex, two one-electron reductions are observed, followed by a two-electron reduction. Presumably these steps correspond to... 

The relation between UV- and PES-spectra is quite similar as found for planar aromatic compounds. All chemical shifts in NMR-spectra can well be explained by normal ring-current effects and Van der Waals interactions. Polarographic data do not deviate from those for planar compounds. 

Despite the drastic solvent limitations, polarographic data could be obtained for MC15 in non-aqueous solvents (Nbv/Nbiv E°= -0.52 V Nblv/Nbu = -0.88 V Tav/Tara E° = -0.88 V in MeCN). Data on molten salts are also available for both metals.1 The reduction of Nbv in aqueous concentrated HC1 solutions proceeds through NbIV, which disproportionates to Nbv and Nbm (assumed to be [NbCL]3-). The NbIV species may be stabilized by addition of ethylene glycol. Further reduction to Nb has been suggested.4... 

From temperature coefficients of polarographic data (ref. 50). h 1,4,7,10-Tetraazacyclododecane, cyclen. 

Polarographic data for pseudoazulenes 26, 27, 39, and 40 have been reported.51 Reduction of azalenes 26 and 39 at a dropping mercury electrode using tetrabutylammonium perchlorate as the carrier electrolyte in acetoni-... 

Katznelson and coworkers494 noted that 96 is a positional isomer of dehydro-L-ascorbic acid (105), as is evident when 96 is depicted in the 1,4-lactone fonn 106 (which, presumably, could exist as 107 or 108). On the basis of polarographic data, Bernaerts and De Ley522 suggested... 

These conditions are fulfilled for the reduction of phenacylsulpho-nium salts at low pH values cleavage of the C—S bond occurs in the first step and proton transfer is involved only in the consecutive steps. The observed shift of half-wave potentials (74) with pH follows the plot predicted by equation (27). The intersection of the two linear parts indicates that phenacylsulphonium salts are moderately strong acids with pK values between 7 and 8 (Fig. 20). Potentiometrically measured pK values, used for verification, are in good agreement with the approximate pK values obtained from polarographic data. The system involved in the first step can be described by scheme (28) ... 

Since the conditions in polarographic reductions are usually quite similar (e.g. temperatures round 20 °C, aqueous, water-containing or water-like solvents), compared with the widely varying conditions used in homogeneous reactions, polarographic data represent a collection which... 

Earlier polarographic data for Os04 have been reviewed (321). The reductions Osvni —> OsVI, OsVI — OsIV, and sometimes OsIV —> Osm have been observed. 

Table 15. Polarographic data in 1 M H2SO4 at 25 °C for MojgO l 6 anion...

Reisenhofer, E., Cesaro, A., Delben, F., Manzini, G., and Paoletti, S. (1984). CoppeKH) binding by natural ionic polysaccharides. Part II. Polarographic data. Bioelectrochem. Bioenerg. 12 455-465 Chem. Abstr. 102 149687, 1985). 

Table IV. Polarographic data for the reduction of halogenated uracils and their glycosides...

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