No abstract

The initial rate of the reaction of I03-with Iin acetate buffer has been measured at fixed ionic strength and acetate concentration with varying concentrations of I03-, I-, and H+ at temperatures between 293 and 308°K. The method involves spectrophotometic determination of the product I3_ at a wavelength of 353 nm. In contrast to some previous results, the reaction is now found to be first order in I03" and second order in H+; the apparent order with respect to Iincreases with temperature in the concentration ranges considered. Agreement with some earlier amperometric results is found. The applicability of previously proposed rate laws and mechanisms is considered, and upper limits are estimated for the enthalpies of possible reactive intermediates.

Electron-impact mass spectra of ferrocene have been obtained at 70 eV with ion-source pressures up to 1.5 X 10 2 Torr at 400°K. Ion-neutral reactions observed are those of Fe+ and FeC\,H< with ferrocene, with rate constants of (2.6 ± 0.5) X 10-9 and (2.4 =fc 0.5) X 10-9 cm3 molecule-1 sec-1, respectively, at a nominal repeller field of 4.6 V cm-1. Reaction of FeC.Hrf with ferrocene gives rise to charge transfer in competition with the formation of the stable adduct Fe2(C5H6)3+. This adduct contributes up to 3% of the total ion current and is formed with a rate constant of (3.4 ± 1.2) X 10-19 cm3 molecule-1 sec-1.

Subjecting carbon suboxide, C302, to electron bombardment in the ion source of a mass spectrometer results in formation of a great variety of positive ions from ion-neutral reactions at sample pressures up to 0.3 Torr. Secondary and higher order ions identified include CzO+ ( x = 3, 4, 5, 6), C"02+ (y = 3, 4, 5, 6, 7, 8, 9), and C,03+ (z = 5, 7). From consideration of the pressure dependence of ionic abundances, possible reactions are suggested. Insertion of carbon atoms from C302 into reactant ions seems to be an important process. Ion-neutral reactions may provide a path for formation of elemental carbon, but there is no evidence here that they lead to polymerization of C302. The rate constant for reaction of C20+ with C302 is (2.1 ± 0.2) X 10-9 cm3 molecule-1 sec-1.Previous mass spectrometric studies of C302, carbon suboxide or dioxopropadiene, are those of Hirt and Wightman,1 Better,2 and Bayes,3 who obtained "low" pressure spectra. Better reported small quan-

A mass-spectrometric study of ion–neutral reactions occurring in CO2 subjected to electron impact yields rates in agreement with previous studies for reaction of C+ and O+ with CO2. Charge transfer from O+ to CO2 is believed to compete with formation of O2+ in these experiments. Reaction of CO+ with CO2 is found to be somewhat faster than previously reported. An approximate rate has been obtained for loss of CO22+. The great abundance of C2O4+ in this system at pressures near 1 torr results from reaction of CO2+ with several CO2 molecules. This reaction is not well understood but a mechanism involving stepwise ion polymerization followed by collision-induced decomposition of the complex to C2O4+ is suggested.