The electrochemical behavior of quinone, hydroquinone, and quinhydrone in pyridine solution at the stationary pyrolytic graphite electrode has been studied by conventional and cyclic voltammetry. In the absence of available protons, quinone is somewhat reversibly reduced in a probable 1e process to a free radical anion; in the presence of protons, the free radical produced on 1e reduction is thought to be oxidized to an N‐dihydroxyphenyl pyridinium ion. The latter is also a likely product from the oxidation of hydroquinone. The quinone‐hydroquinone system itself is irreversible, e.g., quinhydrone behaves as a mixture of quinone and hydroquinone, the potentials of whose waves are 0.5v apart.

It is useful to change the place of (ir) from the sum to the derivative of the concentration. This is permissible because of the properties of the Laplace transformation. Substituting Equation 46into Equation 45and changing the place of t as indicated results in the final equation:Equation 47 represents the first theoretical description of the currentpotential curve for a rotating disk electrode when the potential varies linearly with time and the current varies as a function of the potential. This equation is reduced to that for the stationary electrode case when = <*> (7). The integral indicated in Equation 47 must be computed numerically. LITERATURE CITED(1) Bowers, R.

No abstract

DiscussionThe data of Table I clearly show that the average absorption int,ensity differences between the cyclot risiloxanes, cyclotetrasiloxanes, and higher cyclics are much larger than the standard deviations for each group of cyclics. The differences between the cyclopentasiloxanes and the cyclohexasiloxanes do not appear to be significant.If we consider the geometric configurations of these c.yclics in order of increasing ring size, we find that the average angle between the substituents on successive silicon atonis and conseqiiently the average distance between these substituents will decrease as the ring size increases. These changes in intergroup distance as the ring size changes from cyclotetrasiloxane to cyclopentasiloxane to cyclohexasiloxane could be less important as opportunity for ring puckering increases in the larger rings. Cases of rigidly enforced proximity and orientation of phenylene groups are found in the paracyclophanes a,nd lJ4-polymethylenebenzene cyclics studied by Cram3 and in the siloxane analog of the paracyclophanes studied by M a~K a y .~ MacKay's compound is 13, No. 6, 181 (1958). (3) M. A. Greenbaum, J. N. Foster, M . L. Arin, and M. Farher, J.

No abstract