摘要:

We studied the conditional stability constants of cadmium(II) bound to fulvic acid derived from water and soil, and found that (1) stability constants increased with increasing pH, and (2) stability constants decreased as we increased the fulvic acid concentration toward 70 mg/L. The second effect does not occur for the copper(II)–fulvate system. Conformational changes that occur when a fulvic acid solution becomes more concentrated apparently weaken sites that are otherwise more accessible to weak-binding cadmium. From pH 4 to 8, the overall conditional stability constant increases from 1.4 to 12 × 103for water-derived fulvic acid and from 1.7 to 43 × 103for soil-derived fulvic acid. Increases in fulvic acid concentration from 20 mg/L to 70 mg/L halve the conditional stability constant at a given pH.

ISSN:0008-4042    

DOI:10.1139/v79-206

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The reactions of O(3P) withn-propanol and isopropanol were studied as a function of temperature. The absolute rate constants for these reactions, in the unitsM−1s−1, obey the following relations.The activation energies of these reactions are similar to those of the corresponding reactions of methanol and ethanol, although some dependence on the strength of the α-C—H bond is discernible. The nearly constant pre-exponential factors for the reactions of methanol, ethanol,n-propanol, and isopropanol suggest that no special steric effects are present in the reactions of these compounds with O(3P). Mechanisms are discussed for the reactions ofn-propanol and isopropanol with O(3P).

ISSN:0008-4042    

DOI:10.1139/v79-207

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v79-208

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Spin–lattice relaxation times are reported for the cyano, methylene, and ring carbons in liquid benzyl cyanide at selected temperatures between 215 and 406 K. The rotation of the molecule is modelled on the diffusion of a prolate spheroid and the following features are deduced: (1) rotation of the aromatic ring about the long axis of the molecule is about 3 times faster than rotation of this axis, (2) rotation of the —CH2CN group about the long axis is about 1.5 times faster than the aromatic ring, and (3) activation energies associated with the temperature dependence of the13C—1H dipolar relaxation rates agree with the hydrodynamical prediction of 3.6 kcal/mol associated with the temperature dependence of the ratio shear viscosity–temperature.Linewidths of the cyano carbon resonance are shown to result from scalar coupling with14N.Spin–spin coupling constants involving the cyano and methylene carbons are reported and compared with those calculated at the INDO level of molecular orbital theory.

ISSN:0008-4042    

DOI:10.1139/v79-209

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

HeI photoelectron spectra are reported for pure gas-phase samples of the unstable methylbromamines, CH3NHBr, CH3NBr2, and (CH3)2NBr. Results are also presented for the unsubstituted bromamines NH2Br and NHBr2obtained as products from a gas-phase mixing of NH3and Br2. The spectra are compared with those of the corresponding chloramines.

ISSN:0008-4042    

DOI:10.1139/v79-210

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Pentasulfur hexanitride, S5N6, has been prepared in good yield by the reaction of [n-Bu4N+][S4N5−] with bromine (or iodine) in methylene chloride at 0 °C. In contrast, the tetrasulfur pentanitride(−1) ion reacts smoothly with chlorine to give S4N5Cl, while the reaction with sulfuryl chloride produces S4N5ClandS5N6and the reaction with thionyl chloride produces a mixture of S3N2O, S3N2O2, S4N4, and S5N6. Pentasulfur hexanitride is an air-sensitive, explosive, yellow-orange solid which sublimes at ca. 45 °C/10−2 Torr without significant decomposition. It has been characterised by infrared, Raman, uv–visible, and mass spectra and by a single crystal X-ray structure determination. The crystals are monoclinic and belong to the space groupC2/c,a = 8.787(2),b = 11.190(2),c = 7.427(2) Å, β = 106.46(2)°,V = 700.3(5) Å3,Z = 4,Dc = 2.317 g cm−3. The refined structure (Rw = 0.040) has twofold symmetry and resembles a basket in which an —N=S=N— unit (d(S—N) = 1.54 Å) is the handle which bridges an S4N4cradle via S—N single bonds (d(S—N) = 1.70 Å). The introduction of this bridge widens one of thetransannular separations in S4N4to 3.94 Å while the other is shortened to 2.43 Å. Thus, the S4N4cradle can be viewed as two five-membered rings fused at the S—S bond.

ISSN:0008-4042    

DOI:10.1139/v79-211

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The polarographic reduction of phenolphthalein, cresolphthalein, thymolphthalein, and α-naphtholphthalein has been studied in ethanolic Britton–Robinson buffer series (pH 2–12), non-aqueous ethanolic medium, and water–ethanol mixtures. The compounds are reduced through a single 2e−wave in non-aqueous medium and aqueous buffered solutions of pH < 9 or 1e−steps for pH > 9. The nature of the waves, mechanism of the electrode reaction, and kinetic parameters has been considered.

ISSN:0008-4042    

DOI:10.1139/v79-212

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The oxidation of various diazirines bym-chloroperoxybenzoic acid as well as the activation parameters for these reactions have been investigated. The oxidation products and the information derived from kinetic studies indicate that the oxidation does not take place on the diazirine ring as expected but rather on the decomposition products of the diazirines. The oxidation products obtained are shown to be characteristic of the diazirine decomposition by carbenic and diazo pathways and thus the measurement of the oxidation products provides a measure of the partitioning of the two reaction pathways for diazirine decomposition.

ISSN:0008-4042    

DOI:10.1139/v79-213

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The fundamental processes underlying phase changes at electrode surfaces are often described in terms of the Kolmogoroff–Avrami theorem.Some aspects of the 'fine structure' of this theorem are considered. Particular attention is paid to the case of two-dimensional nucleation and growth under the influence of an applied electrode potential (equivalent to supersaturation). A probabilistic analysis is presented for circularly-symmetric nuclei which obviates the need for concepts such as 'overlap' between emergent nuclei. The concept of a 'collision front' is introduced which is defined as the line of contact along which neighbouring nuclei collide. It is shown that for instantaneous nucleation (potentiostatic double step method) the extended set of collision fronts constitutes a net composed of irregular convex polygons. The properties of this net are investigated in some detail. In particular, the extent of applicability of the Kolmogoroff–Avrami equation is delineated, the distribution of collisional polygons is calculated, and an approximate treatment for the variance of the surface coverage function is presented. The general approach exposes clearly the relationship between the single nucleus and the multinuclear situations.

ISSN:0008-4042    

DOI:10.1139/v79-214

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Vapour–liquid equilibrium data for dilute sulfur dioxide solutions in sixteen solvents were derived from total vapour pressure measurements at 25 °C. The SO2enthalpies of solution at infinite dilution ΔH0were determined at 25 °C by direct calorimetry. The solvents used belong to the aprotic class. The ΔH0values (kcal mol−1) are for the non-polar solvents, isooctane (−3.5), cyclohexane (−3.5),n-heptane (−3.8), benzene (−5.8), and for the polar solvents, 1,2-dichloroethane (−5.5), nitromethane (−6.2), nitrobenzene (−6.3), acetonitrile (−6.7), ethyl acetate (−7.1), sulfolane (−7.3), propylene carbonate (−7.5), trimethyl phosphate (−8.9), tetrahydrofuran (−9.4), dimethylformamide (−10.9), pyridine (−11.6), dimethylsulfoxide (−13.0). Out of three correlation methods which we tested to account for our data in non-polar solvents, the Hildebrand solubility parameter treatment gives the best results. The SO2enthalpies of solution, ΔH0, in the polar solvents are discussed in terms of solvent basicity. There is a good correlation between the ΔH0values, which relate to the basicity of the bulk solvent, and the solvent 'donor number' which is a molecular basicity parameter.

ISSN:0008-4042    

DOI:10.1139/v79-215

出版商:NRC Research Press    

年代:1979

数据来源: NRC