摘要:

Rate constants were determined for the reactions of O(3P) atoms with allene and with 1,3-butadiene by a phase shift technique in which oxygen atoms were generated by modulated mercury photosensitized decomposition of nitrous oxide and monitored by the chemiluminescence from their reaction with NO. Over the temperature interval 297–574 K, the Arrhenius equation for the O(3P) + allene reaction isk1A = (2.99 ± 0.41) × 10−11exp [(−941 ± 54)/T] cm3molecule−1s−1, where the indicated uncertainties are 95% confidence limits. At 299 and 488 K, the rate constant for O(3P) + 1,3-butadiene is essentially the same, within 10%, with an average value of 2.07 × 10−11 cm3molecule−1s−1.

ISSN:0008-4042    

DOI:10.1139/v79-156

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The infrared induced decomposition of vinyl chloride has been studied as a function of pressure and as a function of exciting wavelength with a pulsed CO2laser. The main reaction gives C2H2and HClbut smaller amounts of C2H4are observed. At pressures below 0.5 Torr, the yield of C2H4shows apparent enhancement relative to C2H2. In an earlier publication it had been speculated that this was due to dissociation from higher vibrational levels attained in the multiphoton absorption process. Present data indicate this is not the case and suggest rather strongly that the enhanced C2H4yield is derived from infrared induced decomposition of C2H3Cl on cell windows and walls.The effective quantum yield of C2H2increases approximately linearly with pressure in the range 0–2.5 Torr and C2H3Cl, H2, and O2produce similar behaviour. This is interpreted in terms of collisional enhancement of photon absorption associated with depletion of specific rotational states by the laser radiation.

ISSN:0008-4042    

DOI:10.1139/v79-157

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The31P nmr spectra of the compoundscis-[M(CH3)(L)diphos]PF6, where M = Pd, Pt; L = 4-C5H4NX; X = CH3, H, NMe2, COOMe, COMe, CN; diphos = 1,2-bisdiphenylphosphino ethane, have been recorded. The31P chemical shifts and31P–195Pt coupling constants decrease regularly as the ρ values of the substituent on pyridine decrease. These trends are attributed to decreasing lone pair donation from phosphorus as the electron donating ability of the other ligands on the metal increases. Thetransinfluence of the coordinated pyridine molecule, as measured byJ(195Pt–31P), is greater than itscisinfluence on the phosphorus atoms.

ISSN:0008-4042    

DOI:10.1139/v79-158

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Standard free energies (ΔGt0) and entropies (ΔSt0) of transfer of HX (X = Br and I) from water to glycerol–water mixtures containing 10, 30, 50, and 70 wt.% glycerol have been determined from emf measurements on the cell: Pt, H2(g, 1 atm)/HX(m), solvent/AgX–Ag at seven equidistant temperatures ranging from 10–40°C. The observed ΔGt0–composition profiles of HBr, HI, and also of HCl obtained from the relevant literature data are essentially similar to those in aquo-alcoholic and aquo-glycolic systems. But the observed short maxima inTΔSt0(HX)–composition profiles with their relative order: HI > HBr > HCl in water-rich compositions and the reverse order at higher proportions of glycerol are indicative of the effect of small structure promoting propensity of glycerol. Comparison ofTΔSt0(HI)–composition profiles of methanol, isopropanol, andtert-butyl alcohol on the one hand and that of methanol, ethylene glycol, and glycerol on the other, leads us to suggest that the structure promoting ability of hydrophobic —CH3group is significantly reduced due to 'specific site hydration' effect when its one H-atom is being replaced by one hydrophilic —OH group. Also, the compositions at which the characteristic maxima appear, either in the former cases or in the latter, are, as expected, the size effect of the co-solvents.

ISSN:0008-4042    

DOI:10.1139/v79-159

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Crystalline pentaiodinium hexafluoroantimonate was prepared by the reaction of I2and SbF5in AsF3. The crystals were triclinic,a = 8.295(4) Å,b = 15.61(1) Å,c = 8.390(4) Å, α = 81.49(4)°, β = 110.02(4)°, γ = 85.06(4)°,Z = 3, space group. The structure was solved by multiple-solution direct methods and Fourier syntheses and refined by full-matrix and blocked-matrix least-squares procedures to a finalRof 0.062 andRwof 0.090 for 2229 reflections withI ≥ 3σ(I). The two crystallographically independent planar, bent I5+chains (one centrosymmetric, the other essentially centrosymmetric), each have two collinear central bonds of 2.899(2) Å (× 2); 2.896(2), and 2.920(2) Å, bond angles 180° and 178.7(6)°, respectively, and two shorter terminal bonds of 2.680(3) Å (× 2); 2.666(3) and 2.698(2) Å, with bond angles between central and terminal bonds of 94.53(6)° (× 2); 93.86(7) and 93.17(7)°, respectively. Three I5+units are joined by a weak (3.416(3) Å) interaction to form what may be regarded as an I153+unit. The SbF6−anions are approximately octahedral.

ISSN:0008-4042    

DOI:10.1139/v79-160

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Measurements of the solubility of lead sulphate in 35% by weight sulphuric acid, pure water, and at two intermediate acid concentrations have been made over the temperature range 25 °C to −50 °C using differential pulse anodic stripping voltammetry.Values of the standard enthalpy of solution, derived from the data and from that of other workers, have been found to be higher than those obtained from emf measurements. The extent of lead sulphate ion pairing is analyzed at 25 °C and discussed. The slowness of equilibration of acid solutions supersaturated with lead sulphate was judged of importance in deciding the relevance of the use of thermodynamically calculated lead ion concentrations with respect to lead acid battery mechanisms.

ISSN:0008-4042    

DOI:10.1139/v79-161

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The interaction of aqueous PdCl42−with ethylene to form π-complexes has been reinvestigated using a reactor with high efficiency gas-liquid mixing. This reactor permitted study of the equilibria at low [H+] and [Cl−], the conditions under which the oxidation of ethylene to acetaldehyde proceeds rapidly.Previously the π-complex formation had been determined at high [H+] and [Cl−] to retard the oxidation reaction which interfered with study of the non-oxidative equilibria.Two equilibria reactions were reported whereK1andK2have appreciable values.The present measurements giveK1values close to those previously reported:K1 = 19.6 at μ = 2 M(adjusted with NaClO4); 11.0 at μ = 3 M(adjusted with NaClO4); and 14.7 at μ = 3 M(adjusted with LiClO4). However, theK2values are much less than those reported earlier. Thus the maximum possible value ofK2at μ = 3 M(LiClO4) consistent with the present data is less than 0.01 while the previously reported value was 0.22. Possible reasons for the differences between the two studies are discussed.The values of the aquation constantKhneeded for treating the gas uptake data were determined spectrallyand found to be 0.012 at μ = 2 Mand 0.0060 at μ = 3 M(NaClO4). Spectra taken at high [Pd(II)] indicate dimeric species arenotformed under these conditions.

ISSN:0008-4042    

DOI:10.1139/v79-162

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The anodic oxidation of sodium acetate in the presence of a series of 1,2-disubstituted ethylenes was performed in acetonitrile–water solution. Under low concentration of substrates, very good yields of the monomeric 1,2-dimethylated products were obtained. In the case of diethyl fumarate, an increase in concentration caused a decrease in the ratio of monomer to polymer when all other parameters were held constant.The stereoisomers of the products were separated and their physical properties are reported.

ISSN:0008-4042    

DOI:10.1139/v79-163

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The reactions of SiF4, Si2F6, and SiF2with PH3, CH3PH2, (CH3)2PH, (CH3)4P2, HSCH3, and HSi(CH3)3have been studied. Several new compounds resulting from insertion of Si—F containing units into P—H, S—H, or Si—H bonds have been identified.

ISSN:0008-4042    

DOI:10.1139/v79-164

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A spectrophotometric study of diphenylmethyllithium (DPM−Li+) and diphenylmethyl-potassium (DPM−K+) in ethereal solvents has yielded information on ion pairing and solvation phenomena in these carbanion systems. Different spectral absorptions are observed, characteristic of two types of contact ion pairs (unsolvated and partially solvated) as well as the solvent separated ion pair species, on varying the cation and solvent. This contrasts with our previous observations with triphenylmethyl alkali metal salts where only contact and solvent separated ion pairs were observed. The effect of 18-crown-6 polyether and the effect of temperature changes on the ion pairing equilibria are evaluated. Thermodynamic parameters are obtained for equilibria pertaining to the DPM−Li+/THF and DPM−Li+/DME systems. The results are discussed in relation to literature reports on ion pairing in these systems as derived from nmr studies. Comparison with triphenylmethyl alkali metal salts yields information relating to delocalization and steric effects on ion pairing.

ISSN:0008-4042    

DOI:10.1139/v79-165

出版商:NRC Research Press    

年代:1979

数据来源: NRC