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The stoichiometry and the kinetics of oxidation of the cyanide complexes M(CN) n 4- (M = Fe(II), Ru(II), Os(II), Mo(IV), and W(IV)) by the peroxydisulfate ion, S 2 O 8 2-, and by the much more strongly oxidizing fluoroxysulfate ion, SO 4 F-, were studied in aqueous solutions containing Li + . Reactions of S 2 O8 2 - with M(CN) n 4 - are known to be strongly catalyzed by Li + and other alkali metal ions, and this applies also to the corresponding reactions of SO 4 F-. The primary reactions of S 2 O 8 2- and SO 4 F- have both been found to be one-electron processes in which the equally strong O-O and O-F bonds are broken. The primary reaction of S 2 O8 2 - consists of a single step yielding M(CN) n 3- , SO 4 -, and SO 4 2-, whereas the primary reaction of SO 4 F- comprises two parallel one-electron steps, one leading to M(CN) n 3 -, SO 4 -, and F- and the other yielding M(CN) n -1 2- , CN - , SO 4 - and F-. The relationship between the rate constants and the standard free energies of reaction for the Li + -catalyzed reactions of SO 4 F- and S 2 O 8 2- with M(CN) n 4- , and for the uncatalyzed reactions of S 2 O 8 2- with bipyridyl and phenanthroline complexes ML n 2+ (M = Fe(II), Ru(II), and Os(II)) studied previously, suggests that the intrinsic barrier for all three sets of reactions is similar, i.e., unaffected by the Li + catalysis, and that the electron transfer and the breakage of the O-O and O-F bonds are concerted processes.

Our efforts to model the oxygen activation chemistry of nonheme iron enzymes have yielded transient intermediates with novel properties. These properties can be dramatically affected by the introduction of a 6-methyl substituent on the pendant pyridines of the tetradentate ligand TPA (TPA = tris(2-pyridylmethyl)amine). A series of Fe(TPA) complexes has thus been synthesized and characterized to provide the structural basis for these dramatic effects. The following complexes have been obtained: [Fe(L)(CH3CN)2](ClO4)2 (1, L = TPA; 2, L = 6-MeTPA; 3, L = 6-Me2TPA; 4, L = 6-Me3TPA) and [Fe(L)(acac)](ClO4)2 (5, L = TPA; 6, L = 5-Me3TPA; 7, L = 6-MeTPA). As indicated by 1H NMR and/or EPR, 1, 5, and 6 with no 6-methyl substituent are low spin, while complexes 2, 3, 4, and 7 with at least one 6-methyl substituent are all high spin, with higher redox potentials than their low-spin counterparts. The ligands with 6-methyl substituents thus favor a metal center with a larger ionic radius, i.e., FeII over FeIII and h...

Methylrhenium dioxide, CH3ReO2 (or MDO), is produced from methylrhenium trioxide, CH3ReO3 (or MTO), and hypophosphorous acid in acidic aqueous medium. Its mechanism is discussed in light of MTO's coordination ability and the inverse kinetic isotope effect (kie): H2P(O)OH, k = 0.028 L mol-1 s-1; D2P(O)OH, k = 0.039 L mol-1 s-1. The Re(V) complex, MDO, reduces perchlorate and other inorganic oxoanions (XOn-, where X = Cl, Br, or I and n = 4 or 3). The rate is controlled by the first oxygen abstraction from perchlorate to give chlorate, with a second-order rate constant at pH 0 and 25 °C of 7.3 L mol-1 s-1. Organic oxygen-donors such as sulfoxides and pyridine N-oxides oxidize MDO to MTO as do metal oxo complexes: VO2+(aq), VO2+(aq), HOMoO2+(aq), and MnO4-. The reaction between V2+(aq) with MTO and the reduction of VO2+ with MDO made it possible to determine the free energy for MDO/MTO. Oxygen-atom transfer from oxygen-donors to MDO involves nucleophilic attack of X−O on the electrophilic Re(V) center of M...

Peroxynitric acid, HOONO{sub 2}, can be prepared in aqueous solution by the reaction of nitrous acid with a greater-than-2-fold excess of hydrogen peroxide at or below 0{degrees}C. Under optimum conditions, concentrations in excess of 1.5 M can be obtained. In acid solution at room temperature, the compound has a ca. 30 min half-life for decomposition; in alkaline solution, decomposition is very rapid, yielding nitrite ion and oxygen. The aqueous acid is a potent oxidizing agent, reacting rapidly with I{sup {minus}}, Br{sup {minus}}, N{sub 3}{sup {minus}}, and VO{sup 2+}. Raman, UV, and {sup 15}N NMR spectra of the aqueous acid have been obtained. The Raman spectra reveal three new fundamental vibrations of the peroxynitric acid molecule, leaving only two that have yet to be positively identified. The UV spectrum shows a monotonic rise in absorbance between 290 and 230 nm; the {sup 15}N NMR resonance has a chemical shift of -28.3 ppm relative to dilute nitric acid.

A new oxygen-isotope-sensitive Raman band was found for oxyhemoglobin (HbO[sub 2]) and oxycytochrome c oxidase (CcO[center dot]O[sub 2]) in the frequency region lower than the Fe-O[sub 2] stretching mode ([nu][sub Fe-O2]). This band was located at 425 cm[sup [minus]1] for Hb[sup 16]O[sub 2] and shifted to 405 cm[sup [minus]1] with Hb[sup 18]O[sub 2] and to approximately 423 and approximately 407 cm[sup [minus]1] with Hb[sup 16]O[sup 18]O. The corresponding band appeared at 435 cm[sup [minus]1] for CcO[center dot][sup 16]O[sub 2] and shifted to 415 cm[sup [minus]1] with CcO[center dot][sup 18]O[sub 2]. Accordingly, the band has been assigned to the Fe-O-O bending mode (delta[sub FeOO]). However, the corresponding band could not be identified for oxymyoglobin (MbO[sub 2]). The Fe-O[sub 2] stretching mode ([nu][sub Fe-O2]) was observed at 568, 567, 544, and 544 cm[sup [minus]1] for Hb[sup 16]O[sub 2], Hb[sup 16]O[sup 18]O, Hb[sup 18]O[sup 16]O, and Hb[sup 18]O[sub 2], respectively, and the corresponding modes were observed at 571, 569, 547, and 545 cm[sup [minus]1] for MbO[sub 2] and 571, 567, 548, and 544 cm[sup [minus]1] for CcO[center dot]O[sub 2]. The [nu][sub Fe-O(2)] bandwidths of HbO[sub 2] and MbO[sub 2] were alike and 1.5 times broader than that of CcO-O[sub 2], suggesting that themore » Fe-O-O geometry is more nearly fixed in the latter. 44 refs., 6 figs., 1 tab.« less

Time-resolved resonance Raman (RR) spectra were observed for catalytic intermediates of bovine cytochrome c oxidase at room temperature by using an Artificial Cardiovascular System for Enzymatic Reactions and Raman/Absorption Simultaneous Measurement Device. The isotope-frequency-shift data using an asymmetrically labeled dioxygen, [sup 16]O[sup 18]O, established that the primary intermediate (compound A) is an end-on-type dioxygen adduct of cytochrome a[sub 3]. Higher resolution RR experiments revealed that the approximately 800-cm[sup [minus]1] band assigned previously to the Fe[sup TV]= O stretching mode of the subsequent intermediate (compound B) was actually composed of two bands that behaved differently upon deuteration. The 804/764-cm[sup [minus]1] pair for the [sup 16]O[sub 2]/[sup 18]O[sub 2] derivatives were insensitive to deuteration, and these bands became noticeably stronger at higher temperatures. The present experiments have conclusively established that the main pathway for dioxygen reduction by cytochrome c oxidase is Fe[sup II]-O[sub 2] [yields] Fe[sup III]-O-O-H [yields] Fe[sup IV]=O [yields] Fe[sup III]-OH and that their key bands for the [sup 16]O[sub 2]/[sup 18]O[sub 2] pair are at 571/544, 785/751, 804/764, and 450/425 cm[sup [minus]1], respectively. 79 refs., 8 figs., 3 tabs.

tert-Butyl hypofluorite ((CH[sub 3])[sub 3]COF) can be synthesized by the low-temperature reaction of elemental fluorine with tert-butyl alcohol dissolved in propionitrile or acetonitrile. The isolated compound, which melts around -94[degrees]C and has an extrapolated boiling point of about +40[degrees]C, has been characterized by mass, NMR, and IR spectrometry. The [sup 19]F NMR shift of +67 ppm lies between the corresponding shifts of HOF and CH[sub 3]OF and implies a rather high O-F bond energy. Although sterically crowded, tert-butyl hypofluorite adds to olefins to form [beta]-fluoro-tert-butoxy compounds. Addition is mainly in an anti mode, and the regioselectivity corresponds to the action of a hitherto unknown tert-butoxylium electrophile. Also formed are adducts containing F and CH[sub 2]CN, the latter deriving from the acetonitrile solvent. 19 refs., 1 tab.

Methyl hypofluorite (CH 3 OF) has been prepared by the reaction of elemental fluorine with methanol in acetonitrile or propionitrile at low temperature. It was removed from the reaction mixture in a stream of nitrogen and purified by fractional distillation. The compound is moderately long-lived, although the liquid has exploded upon rapid warming. The liquid compound has a freezing point of about −142°C, and vapor pressure measurements indicate a normal boiling point of −32.6±0.9°C and an enthalpy of vaporization of 23.37±0.26 kJ/mol. The infrared spectrum of the vapor is consistent with the molecule being isostructural with CH 3 OH and CF 3 OF. The compound has also been characterized by mass spectrometry and by 1 H, 19 F, and 13 C NMR spectrometries. This novel reagent adds across various double bonds to form the corresponding fluoro methoxy adducts, which are not easily accessible by other methods

Ozone in the presence of hydrogen peroxide has been employed succesfully for the oxidative degradation of polycarboxylic and diphosphonic acid chelating agents present at the 0.1 M level in a neutral or weakly alkaline aqueous solution. The geminal diphosphonic acid complexants methanediphosphonic acid and (1-hydroxyethylidene)bisphosphonic acid have been successfully mineralized, as have the polycarboxylic acids ethylenediaminetetraacetic acid and tetrahydrofurantetracarboxylic acid.

Trifluoromethanesulfonyl hypofluorite (CF[sub 3]SO[sub 2]OF) has been synthesized by the reaction of fluorosulfuryl hypofluorite (FSO[sub 2]OF) with cesium trifluoromethanesulfonate. It is the first compound in which a sulfur atom is bonded both to carbon and to an O-F moiety. The compound has a melting point of -87 [plus minus] 2[degrees]C and an extrapolated boiling point of 0 [plus minus] 1[degrees]C. The [sup 19]F NMR spectrum of the compound in CFCl[sub 3] at -80[degrees]C shows a CF[sub 3] doublet at -71 ppm and a broad OF singlet at +238 ppm. From the latter can be deduced an O-F bond energy of about 145 kJ/mol, comparable to that of FSO[sub 2]OF. The compound hydrolyses in base to give a mixture of O[sub 2] and CF[sub 4], along with (presumably) sulfate and trifluoromethanesulfonate. It decomposes thermally in the presence of CsF to yield principally CF[sub 3]SO[sub 2]F and OF[sub 2] along with (presumably) cesium trifluoromethanesulfonate. 14 refs., 1 tab.

We present new optical and resonance Raman spectroscopic data that characterize the first intermediate as a diiron(III) peroxo species. The time-resolved optical and freeze-quench resonance Raman spectroscopic experiments strongly support assignment of the first intermediate, variously designated P or L, in the MMO hydroxylase reaction cycle as a symmetrical diiron(III) peroxo species. 32 refs., 2 figs.

Alkaline solutions of seven-valent neptunium in water enriched in oxygen-17 show a /sup 17/O NMR resonance about 1470 ppM downfield from the solvent resonance. Measurement of relative areas indicates that the Np(VII) oxygen resonance contains about four oxygen atoms per Np atom. This result is interpreted in terms of the six-coordinated Np(VII) anion NpO/sub 4/(OH)/sub 2//sup 3/minus//, in which four oxygen atoms are present in a square plane around the Np and are responsible for the observed resonance. The two hydroxyl groups are located further from the Np at the vertices of a tetragonal bipyramid and presumably exchange too rapidly with solvent oxygen for their /sup 17/O resonance to be seen. The Np(VII) oxygen resonance has a line width that increases with temperature and is around 400 Hz at 25/degree/C. The temperature dependence of the line width can be accounted for by a process of oxygen exchange between the Np(VII) species and the solvent, with a pseudo-first-order rate constant of about 10/sup 3/s/sup /minus/1/ at 25/degree/C. No Np(VI) oxygen resonance was observed in alkaline solution, probably because the Np(VI) oxygens exchange too rapidly with the solvent. 21 references, 2 tables.

The infrared spectrum of the hypofluorous acid molecule, HOF, trapped in different solid matrices at low temperatures shows that the vibrational fundamentals {nu}{sub 1} and {nu}{sub 2} are perturbed to extents that vary with the basicity of the adjacent molecule, D, and the appearance of absorptions attributable to librational motions of the D{hor ellipsis}H-OF unit implies the formation of specific hydrogen-bonded complexes in some cases. As the matrix concentration of HOF increases, aggregation occurs to give (HOF){sub 2} and higher multimers. Exposure of HOF isolated in an Ar matrix to broad-band ultraviolet radiation results in photodissociation with the formation of two products thought to be O{hor ellipsis}(HF){sub 2} and O{sub 2}{hor ellipsis}(HF){sub 2} in proportions dependent on the concentration of HOF. Photolysis of HOF trapped in a reactive matrix results in oxygenation of the matrix molecules, X, and complexation of the product XO by HF; e.g. X = N{sub 2}, CO, O{sub 2}, or CH{sub 4}. The CO, O{sub 2}, or CH{sub 4} matrices also yield on photolysis small but significant amounts of FCO{sup {sm bullet}}, O{sub 2}F{sup {sm bullet}}, or CH{sub 3}{hor ellipsis}HF, respectively, products that signal the intervention of fluorine atoms. Photolysis of an Ar matrix including HOFmore » together with a potential substrate, Y, at concentrations > 1% results exclusively in oxygenation, and not fluorination, to give YO (Y = PF{sub 3}, AsF{sub 3}, or H{sub 2}O). The results are discussed in relation to the mechanisms likely to govern the matrix photochemistry of HOF.« less

This paper examines the reactions of F/sub 2/ and HOF with aqueous perchloric acid solutions containing various complexes of trivalent chromium. In no case is the chromium itself oxidized. The complex CrF/sup 2 +/ is unreactive toward either oxidant. CrClO/sub 3//sup 2 +/, CrNO/sup 2 +/, CrCl/sup 2 +/, and CrBr/sup 2 +/ show increasing reactivity, with the formation of Cr/sup 3 +/ as the principal product. In the case of CrBr/sup 2 +/ and CrCL/sup 2 +/ there is evidence that F/sub 2/ can react with the substrate directly, as well as via the intermediate formation of HOF. This direct reaction produces some CrF/sup 2 +/ in addition to Cr/sup 3 +/. Azidochromium(III), CrN/sub 3//sup 2 +/, is the most reactive of the complexes studied. It reacts directly with F/sub 2/ to form a mixture of Cr/sup 3 +/ and CrF/sup 2 +/; it reacts with HOF to form CrNO/sup 2 +/. Reaction mechanisms that can account for these observations are discussed.

The rubidium salt of the recently identified fluoroxysulfate anion, FOSO/sub 3//sup -/, has been characterized by single-crystal X-ray diffraction. RbFOSO/sub 3/ crystallizes in the centrosymmetric triclinic space group, Pl, with unit cell constants a = 5.503 (2) A, b = 5.623 (1) A, c = 7.603 (3) A, ..cap alpha.. = 100.64 (2)/sup 0/, ..beta.. = 106.72 (2)/sup 0/, ..gamma.. = 93.22 (2)/sup 0/, and Z = 2. The X-ray data refine to an R/sub F/ = 0.067 for 664 reflections with F/sup 2/ > sigmaF/sup 2/. The fluoroxysulfate anion has distorted tetrahedral coordination with each central sulfur atom bound to four oxygens. The S-O bond distances are 1.435 (8), 1.426 (8), 1.441 (7), and 1.652 (9) A. The O-F bond distance is 1.412 (10) A, and the S-O-F bond angle is 107.8 (6)/sup 0/. Each Rb/sup +/ cation is coordinated to nine oxygen atoms and two fluorine atoms.

The fluoroxysulfate ion, SO/sub 4/F/sup -/, substitutes fluorine on aromatic compounds in acetonitrile solution at room temperature. However, benzyl fluoride is the principal product from toluene. Other products are also formed, particularly in the case of the less reactive aromatic substrates. Product distributions and relative reactivities are interpreted in terms of an initial electrophilic attack that can be followed by free-radical side reactions.

Resonance Raman spectra of the complex of Fe/sup III/-ethylenediaminetetraacetate with hydrogen peroxide have been obtained in the region of the peroxidic O-O stretching vibration that occurs at 815 cm/sup /minus/1/ in frozen solution. When the complex was prepared from nearly neat, mixed-isotope hydrogen peroxide, H/sub 2//sup 16/O/sup 18/O, a single O-O vibration was observed at 794 cm/sup /minus/1/. This observation establishes that the two oxygen atoms of the bound peroxide are equivalent and that the peroxide is ligated in an /eta//sup 2/ side-on configuration in this mononuclear complex. The absence of any shift in /nu/(O-O) when the complex was prepared in D/sub 2/O solvent provides further support for the side-on Fe(O-O) geometry and rules out the alternative /eta//sup 1/ end-on Fe-OOH configuration. In contrast, /nu/(O-O) of free hydrogen peroxide in the frozen state occurs at 877 cm/sup /minus/1/ in H/sub 2/O and 879 cm/sup /minus/1/ in D/sub 2/O. The 2-cm/sup /minus/1/ upshift in D/sub 2/O is similar to that observed previously with oxyhemerythrin and appears to be characteristic of a hydrogen-bonded or protonated peroxide species. 37 references, 4 figures, 1 table.

Aqueous SO/sub 4/F/sup -/ decomposes to form O/sub 2/, H/sub 2/O/sub 2/, and HSO/sub 5//sup -/. At 15/sup 0/C in 0.01 M HC1O/sub 4/ the first-order rate constant k = 3.6 x 10/sup -4/s/sup -1/, ..delta..H/sup + +/ = 16.8 +- 0.4 kcal/mol, and ..delta..S/sup + +/ = -15.7 +- 1.5 cal/(mol deg). The H/sub 2/O/sub 2/ and O/sub 2/ products both contain one oxygen atom from solvent and one from the fluoroxysulfate. The HSO/sub 5//sup -/ product also contains an atom of solvent oxygen in its terminal peroxide position. A mechanism is proposed in which the rate-determining steps are the interaction of SO/sub 4/F/sup -/ with water fo form HSO/sub 5//sup -/ and H/sub 2/O/sub 2/. The H/sub 2/O/sub 2/ probably interacts further with SO/sub 4/F/sup -/ by means of a free-radical chain reaction to produce O/sub 2/. Fluorosulfate ion, SO/sub 3/F/sup -/, appears to be formed only in the oxygen-transfer step that produces H/sub 2/O/sub 2/. Chlorite ion is rapidly oxidized to C1O/sub 2/ by SO/sub 4/F/sup -/ in accordance with the rate law -d(SO/sub 4/F/sup -/)/dt = k/sub ClO/sub 2//sup -//(ClO/sub 2//sup -/)(SO/sub 4/F/sup -/). In acid solution at 14.7/sup 0/C, k/sub ClO/sub 2//sup -// = 1.8more » x 10/sup 4/ L/(mol s), ..delta..H/sup + +/ = 7.3 +- 0.6 kcal/mol, and ..delta..S/sup + +/ = -14 +- 2 cal/(mol deg). The oxidation of Co(NH/sub 3/)/sub 5/ClO/sub 2//sup 2 +/ by SO/sub 4/F/sup -/ produces ClO/sub 2/ and a mixture of Co(NH/sub 3/)/sub 5/F/sup 2 +/ and Co(NH/sub 3/)/sub 5/H/sub 2/O/sup 3 +/. The oxidation of Cr/sup 2 +/ by SO/sub 4/F/sup -/ produces 42 to 47% Cr/sup 3 +/ and 41 to 45% CrF/sup 2 +/, the balance consisting of polynuclear Cr(III) species. The oxidation of I/sup -/ to I/sub 2/ by SO/sub 4/F/sup -/ consumes no acid and hence does not produce SO/sub 3/F/sup -/. These rapid reactions may be interpreted in terms of mechanisms involving either 1- or 2-equiv oxidation in the rate-determining steps. Oxygen transfer does not appear to be significant, but fluorine transfer is obviously involved at least in the oxidation of Cr/sup 2 +/ and Co(NH/sub 3/)/sub 5/ClO/sub 2//sup 2 +/.« less

The oxidation of azide by peroxymonosulfate has been studied in acid, neutral, and basic solutions, and the oxidation of Cr(NH/sub 3/)/sub 5/N/sub 3//sup 2 +/ by peroxymonosulfate has been studied in acid. The reaction with azide obeys the rate law k/sub 1/(N/sub 3//sup -/)(HSO/sub 5//sup -/) in acid and neutral solution and the rate law k/sub 2/(N/sub 3//sup -/)(SO/sub 5//sup 2 -/) in base. The reaction with Cr(NH/sub 3/)/sub 5/N/sub 3//sup 2 +/ obeys the rate law k/sub 3/(Cr(NH/sub 3/)/sub 5/N/sub 3//sup 2 +/)(HSO/sub 5//sup -/). At 25/sup 0/C, k/sub 1/ = 0.66 L/(mol s), k/sub 2/ = 0.0076 L/(mol s), and k/sub 3/ = 0.013 L/(mol s). Oxygen-18 tracer experiments show that the reactions proceed by transfer of a terminal peroxide oxygen of the peroxymonosulfate to the reductant. 4 tables.

The oxidations of the ions Cr/sup 3 +/, CO/sup 2 +/, and VO/sup 2 +/ by the fluoroxysulfate ion, SO/sub 4/F/sup -/, in aqueous solution are catalyzed by Ag/sup +/. The rate-determining step for all three catalyzed reactions is the bimolecular oxidation of Ag/sup +/ by SO/sub 4/F/sup -/, which has a rate constant of (1.3 +- 0.2) x 10/sup 3/ M/sup -1/ s/sup -1/ at 17/sup 0/C. Activation parameters for this reaction are ..delta..H/sup + +/ = 6.1 +- 0.5 kcal/mol and ..delta..S = -23 +- 2 cal/(mol deg). In the absence of Ag/sup +/, Co/sup 2 +/, and VO/sup 2 +/ react very slowly with SO/sub 4/F/sup -/, while Cr/sup 3 +/ does not react at all. Despite its high thermodynamic oxidizing power, the fluoroxysulfate ion acts as a very selective oxidant.

The effects of substitution of fluorine for part of the oxygen on the properties of the superconductor YBa/sub 2/Cu/sub 3/O/sub 6.8/ (YBCO) have been studies. A series of fluorine-containing materials with nominal composition YBa/sub 2/Cu/sub 3/F/sub x/O/sub 6.5-x/2/ (x = 1, 1.5, 2, 2.5, 3) was prepared by mixing YBa/sub 2/Cu/sub 3/O/sub 6.8/ and YBa/sub 5/Cu/sub 3/F/sub 4/O/sub 4.5/. The first three compositions exhibited superconducting transitions with onset temperatures from 75 to 49 K. X-ray powder patterns for all compositions showed the presence of unreacted BaF/sub 2/ which cast doubt on the actual fluorine incorporated into the complex. Several other unsuccessful attempts to incorporate fluorine are reported. The procedure using the reversible oxygen intercalation effect and reaction with F/sub 2/ to introduce fluorine into the 1:2:3 perovskite previously proved to be successful as indicated by x-ray diffraction patterns that showed a broad diffraction peak corresponding to the 1:2:3 YBCO perovskite structure with unresolved orthrhombic/tetragonal splittings and no indication of BaF/sub 2/. No evidence was found for a F-containing superconducting phase formed with T/sub c/ /approx equal/ 155 K. 21 refs., 3 figs., 1 tab.

The gas-phase reaction of mercury with ammonium iodide is the basis of at least one scheme for the thermochemical production of hydrogen. We have studied the reactions Hg + 2HI ..-->.. HgI/sub 2/ + H/sub 2/ and Hg + 2NH/sub 4/I ..-->.. HgI/sub 2/ + H/sub 2/ + 2NH/sub 3/ in the gas phase for 623 to 693 K. Under our conditions NH/sub 4/I is completely dissociated to NH/sub 3/ and HI. The reactions were followed by spectrophotometrically monitoring the buildup of the product, HgI/sub 2/. In the absence of NH/sub 3/ and with approximately 20-fold excess of HI (10/sup -3/ M equal to or less than (HI) equal to or less than 10/sup -2/ M), the rate of appearance of HgI/sub 2/ is given by d(HgI/sub 2/)/dt = k/sub 4/(Hg)(HI). With excess Hg, however, the rate follows the expression d(HgI/sub 2/)/dt = k/sub 5/(Hg)(HI)/sup 2/. Introduction of NH/sub 3/ into the system increases the rate substantially. In the presence of ammonia at concentrations comparable to those of the Hg and HI, the rate law assumes the form d(HgI/sub 2/)/dt = k/sub 3/(Hg)(HI)/sup 2/(NH/sub 3/). At 663 K k/sub 4/, k/sub 5/, and k/sub 3/ have the values 3.7 Lmore » mol/sup -1/ min/sup -1/, 590 L/sup 2/ mol/sup -2/ min/sup -1/, and 2.2 x 10/sup 6/ L/sup 3/ mol/sup -3/ min/sup -1/, respectively. Increasing the surface-to-volume ratio has no discernible effect on the reaction rate. The constant k/sub 3/ has a negative temperature dependence, which corresponds to an activation energy of -34 kJ/mol. The reaction in the presence of ammonia is interpreted in terms of a preequilibrium to form a complex HI . Hg . NH/sub 3/. 4 tables, 5 figures.« less

The infrared and Raman spectra of solid cesium and rubidium fluoroxysulfates, CsSO/sub 4/F and RbSO/sub 4/F, have been measured, along with the gas-phase spectra of the isoelectronic molecule fluorine perchlorate, ClO/sub 4/F. The spectra are consistent with a perchloric acid type structure of C/sub s/ symmetry, and the vibrational bands have been assigned with reference to the analogous species of C/sub 3..nu../ symmetry: the fluorosulfate ion, SO/sub 3/F/sup -/, and perchloryl fluoride, ClO/sub 3/F. Normal-coordinate analyses have been carried out for both ClO/sub 4/F and SO/sub 4/F/sup -/. 6 figures, 4 tables.

Perchlorate and perbromate ions are partially protonated in anhydrous HF, and the Raman spectra of such solutions show peaks attributed both to the anions and to their undissociated conjugate acids. Quantitative analysis of the spectra as a function of concentration permits evaluation of the equilibrium constants for protonation. Perbromic acid is found to have 6 times the acid strength of perchloric acid. From comparison with data on other acids in aqueous solution and in CF/sub 3/CO/sub 2/H, the acid dissociation constant of HBrO/sub 4/ in aqueous solution is estimated to be 10/sup 8.5/. If the relative acidities of HBrO/sub 4/ and HClO/sub 4/ in HF remain the same for the neat acids, HBrO/sub 4/ will have a Hammett acidity function, H/sub 0/, of about -13.8. Relative Raman scattering coefficients for the strongest bands of the two anions and their conjugate acids are also reported. 4 figures, 4 tables

The reaction of the perbromate ion with a number of two-equivalent reductants have been studied in aqueous solution at an ionic strength of approximately one. Reaction rates increase in the order N/sub 3/

This paper elucidates a prominent feature of the fluorine-water reaction: the production of H/sub 2/O/sub 2/ and O/sub 2/. Because this process almost certainly involves the intermediate formation of HOF, the production and consumption of H/sub 2/O/sub 2/ in the reaction of HOF with water and the mechanism of the HOF-H/sub 2/O/sub 2/ reaction are also examined. In addition, an order-of-magnitude estimate of the rate of the homogeneous reaction of F/sub 2/ with water is obtained and the effects of various added substrates are determined. 34 references, 2 figures, 5 tables.

Stopped-flow spectrophotometry was used to study the oxidation of plutonium(III) to plutonium(IV) is 1 M HClO{sub 4} by XeF{sub 2} and by the fluoroxysulfate ion, SO{sub 4}F{sup {minus}}. In both reactions, 2 mol of Pu(III) is oxidized per 1 mol of oxidant consumed, and neither Pu(V) or Pu(VI) appears to be formed either as an intermediate or as an initial product, although an excess of XeF{sub 2} does slowly oxidize the Pu(IV) product to Pu(VI). At 2{degree}C the reactions have respective bimolecular rate constants of 1160 {plus minus} 70 and 120 {plus minus} 9 M{sup {minus}1} s{sup {minus}1}, expressed in terms of -d(Pu(III))/dt. Over the temperature range 2-24{degree}C, the activation parameters for the XeF{sub 2} reaction are {Delta}H{sup {double dagger}} = 39.5 {plus minus} 8.6 kJ/mol and {Delta}S{sup {double dagger}} = {minus}48.3 {plus minus} 29 J/(mol K), while those for the SO{sub 4}F{sup {minus}} reaction are {Delta}H{sub {double dagger}} = 30.8 {plus minus} 2.3 kJ/mol and {Delta}S{sup {double dagger}} = {minus}98.5 {plus minus} 7.8 J/(mol K). Mechanisms are postulated that invoke a sequence of two one-electron-oxidation steps. 24 refs., 2 tabs.

The enthalpies of reaction of cesium fluoroxysulfate, CsSO/sub 4/F, and cesium perocydisulfate, Cs/sub 2/S/sub 2/O/sub 8/, with HI(aq) have been measured by solution calorimetry, and the following standard enthalpies of formation at 298.15 K have been derived: ..delta..H/sub f//sup 0/(CsSO/sub 4/F(c)) = -1004.9 +- 1.6 kJ mol/sup -1/ and ..delta..H/sub f//sup 0/(Cs/sub 2/S/sub 2/O/sub 8/(c)) = -1936.7 +- 2.8 lJ mol/sup -1/. The enthalpy of solution of Cs/sub 2/S/sub 2/O/sub 8/(c) in 5345 mol of water at 298.15 K has been determined to be 79.5 +- 1.9 kJ mol/sup -1/. The Gibbs energy of solution of CsSO/sub 4/F at 298.15 K has been determined from solubility measurements to be ..delta..G/sub soln//sup 0/ (CsSO/sub 4/F) = 6.15 +- 0.40 kJ mol/sup -1/. The fluoroxysulfate results have been used in conjunction with an estimated entropy for solid CsSO/sub 4/F to calculate a standard potential of 2.52 +- 0.05 V at 298.15 K for the half-reaction SO/sub 4/F/sup -/(aq) + 2H/sup +/(aq) + 2e/sup -/ ..-->.. HSO/sup 4 -/(aq) + HF(aq). 8 tables.

Oxygen-18 tracer studies have shown that the reactions of HO*F with H/sub 2/O and with aqueous HSO/sub 4//sup -/ and Cr(NH/sub 3/)/sub 5/N/sub 3//sup 2 +/ lead to transfer of oxygen with formation of HOO*H, O/sub 3/SOO*H/sup -/, and Cr(NH/sub 3/)/sub 5/NO*/sup 2 +/, respectively. Transfer is incomplete in the case of dilute (0.4 M) bisulfate solutions.

Stopped-flow spectrophotometry has been used to study the oxidation of the substitution-inert Ru(II) complex ion Ru(bpy){sub 3}{sup 2+} by the fluoroxysulfate ion, SO{sub 4}F{sup {minus}}. The reaction follows a bimolecular rate law and has 1:1 stoichiometry. At 13.3{degree}C, corrected to infinite dilution, k{sub 2}{degree} = 1346 {plus minus} 19 M{sup {minus}1} s{sup {minus}1}. Over the temperature range 2-24{degree}C, {Delta}H{sup {double dagger}} = 37.1 {plus minus} 1.1 kJ/mol and {Delta}S{sup {double dagger}} = {minus}55 {plus minus} 4 J/(mol K). The rate and stoichiometry are independent of whether the Ru complex is present as a chloride or a perchlorate salt, and the rate does not show a dependence on acidity. The oxidation of coordinated ligands is probably involved. The reaction is among the fastest reactions of SO{sub 4}F{sup {minus}}. 10 refs., 4 tabs.

Studies of the composition of YBa/sub 2/Cu/sub 3/O/sub y/ in which the oxidation states of Y and Ba are +3 and +2, respectively, have shown a direct relationship between the Cu(II)/Cu(III) ratio and the oxygen stoichiometry. Idometry or hydrogen reduction has generally been used for the Cu(III) determination. A modification of the idometric method that is simple to apply and is particularly suited to analyses of La/sub 2-x/Sr/sub x/CuO/sub y/ and YBa/sub 2/Cu/sub 3/O/sub y/ is described. The results of application to determination of the oxygen content of YBa/sub 2/Cu/sub 3/O/sub y/ are presented, and the oxygen content is related to the crystallographic and superconducting properties of the material. Results indicated that at room-temperature large variations of the oxygen content of the orthorhombic phase of YBa/sub 2/Cu/sub 3/O/sub y/ could occur without change in the lattice parameters or appreciable impairment of the resistive superconducting transition or diamagnetic properties. 13 references, 1 figure, 1 table.

The equilibria in the systems KI + NH/sub 4/I + water and KI + NH/sub 4/I + equimolar mixtures of 2-propanol and water have been studied at 25/sup 0/C. The two iodides are completely miscible in the solid phase.

Aqueous solutions of Xe8+ were prepared from the solid sodium perxenate obtained by alkaline hydrolysis of XeF6. At high pH these solutions decompose slowly to Xe6+ and oxygen, the rate increasing with decreasing pH. The standard potential in basic solution for the Xe6+-- Xe8+ couple is estimated to lie between --0.7 and --1.24 v. The ultraviolet spectram of Xe8+ is given as a function of pH, and potentiometric acid-- base titrations of both Xe8+ and Xe6+ are presented. A series of protonation equilibria is postulated to explain the observations.