摘要:

Upon mercury photosensitization, the vibrationally excited triplet of the simple alkenes 1-hexene andcis-2-octene undergoes an olefinic type II reaction consisting of an intramolecular 1,5-hydrogen abstraction via a six-membered transition state and subsequent reaction of the resulting biradical, in sharp contrast to the well established allylic C—C and C—H bond cleavage of alkenes without a γ-hydrogen. Thecis–transphotoisomerization ofcis-2-octene and other intramolecular hydrogen abstractions of minor importance occurring through unfavorable transition states were also observed. The mercury photosensitization of various cyclic and acyclic alkenes so far reported are comparatively discussed.

ISSN:0008-4042    

DOI:10.1139/v76-445

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Densities, viscosities, and refractive indices at 25 °C were determined for the systems:ochlorophenol + N,N-dimethylaniline,o-chlorophenol + aniline,o-chlorophenol + m-toluidine, ando-chlorophenol + pyridine. From the experimental results the excess volume, excess viscosity, excess molar free energy of activation of flow, and the excess partial molar volume were calculated. There is evidence of complex formation betweeno-chlorophenol and the four bases.

ISSN:0008-4042    

DOI:10.1139/v76-446

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Crystals ofB,B-bis(p-tolyl)boroxazolidine,1c, are trigonal,a = 25.1028(9),c = 12.4184(7) Å,Z = 18, space group. And crystals ofB,B-diphenylboroxazolidine,1a, are orthorhombic,a = 17.6420(4),b = 14.2527(3),c = 10.205(1) Å,Z = 8, space groupPbca. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to finalRvalues of 0.057 and 0.040 for 2230 and 1828 reflections withI ≥ 3σ(I) respectively. Both molecules have structures similar to related compounds and feature intermolecular N—H … O hydrogen bonds (N … O = 2.982(2) for1cand 2.896(2) Å for1a). Bond lengths are: for1c; O—C, 1.413(3), O—B, 1.478(3), N—C, 1.488(3), N—B, 1.657(3), C(sp3)—C(sp3), 1.501(4), B—C, 1.616(3) and 1.623(3), mean C—C(ar), 1.395, N—H, 0.93(2) and 0.94(2), mean C(sp3)—H, 1.00, and mean C(ar)—H, 1.00 Å; for1a; O—C, 1.409(2), O—B, 1.476(2), N—C, 1.489(2), N—B, 1.655(2), C(sp3)—C(sp3), 1.507(3), B—C, 1.613(2) and 1.620(2), mean C—C(ar), 1.391, N—H, 0.93(2) and 0.92(2), mean C(sp3)—H, 1.00, and mean C(ar)—H, 0.98 Å. A statistical analysis of the phenyl C—C distances in compounds1a,1b, and1chas provided an example of statistically significant substituent-induced bond length variation in the phenyl rings.

ISSN:0008-4042    

DOI:10.1139/v76-447

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Crystals of 8,8-dimethyl-3,5-diphenyl-2,4,6-trioxa-1-azonia-3-bora-5-boranatabicyclo[3.3.0]-octane are monoclinic,a = 22.323(1),b = 9.555(1),c = 16.0027(6) Å, β = 109.055(4)°,Z = 8, space groupC2/c. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a finalRof 0.048 andRwof 0.066 for 2629 reflections withI ≥ 3σ(I). The central part of the molecule consists of two fused five-membered rings. One of them is a familiar BOCCN ring while the other is a novel and nearly planar BOBON ring containing one tetrahedral boron atom and one trigonal planar boron atom. Bond lengths are: O—B, 1.337(2)–1.467(2), N—B, 1.692(2), O—N, 1.440(2), O—C, 1.426(2), N—C, 1.513(2), B—C, 1.557(2) and 1.599(2), C(sp3)—C(sp3), 1.520(2)–1.530(2), C—C(ar), 1.372(4)–1.407(2), N—H, 0.89(2), mean C(ar)—H, 0.97(1), and mean C(sp3)—H, 1.01(1) Å. The crystal structure consists of discrete molecules each linked to two others by N—H … O hydrogen bonds (N … O = 2.853(2) Å).

ISSN:0008-4042    

DOI:10.1139/v76-448

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Experimental ultrasonic absorption data on solutions of H2SO4and H3PO4are interpreted in terms of proton transfer equilibria. The acid dissociation constants obtained are compared with those obtained using other methods and are shown to be consistently lower. A model is proposed to explain this in terms of ΔVθand ΔHθinvolved in the steps leading to recombination of the proton with the anion. This model is supported by the values of the reaction distance parameters calculated from the value of the rate constant obtained for the recombination rate. The accuracy of this rate constant is dependent on the accuracy of the ΔVθvalue used for the equilibrium. Experimental density data are presented here as an aid in determining ΔVθ. Problems involving activity coefficients in such solutions are discussed in the course of checking the values used for species present in sulfuric acid solutions.

ISSN:0008-4042    

DOI:10.1139/v76-449

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Heats of formation of hydrates may be measured by dissolving the hydrate and the corresponding anhydrate in water to attain the same final concentration and measure the difference in heats of solution.Measurements were made at 0 °C in a modified Bunsen ice calorimeter, well insulated, and surrounded with an ice–water mixture.The data obtained are a measure of the enthalpy involved in binding a mole of water into a crystal structure, to shed some light on the nature and mechanism of this binding. Several discrepancies are noted, in particular one involving. A method for adjusting calculations from 0 to 25 °C in the absence of heat capacity data is proposed.The following hydrates have been studied: LiCl•H2O, LiBr•2H2O, CaCl2•2 and •6H2O, MnCl2•1 and •2H2O,, MnSO4•1 and •4H2O, MgSO4•1, •4(?), and •7H2O, and.Additionally, the heat of hydration of hydrazine to N2H4•H2O has been checked.The formation of a coordinated hydrate, from liquid water, involves a heat effect which in the limit approaches 3 kcal mol−1. The first mole of water added may be most strongly bonded (6–10 kcal), possibly since alternate sites in the coordination sphere may be available to it.Values which differ markedly from these levels deserve a critical examination. Higher values may suggest the presence of OH−, or other structural variations, errors in the published data or mistaken identification of the hydrate.

ISSN:0008-4042    

DOI:10.1139/v76-450

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Complexes of lanthanide iodides with 3-methylpyridine-1-oxide of the formula Ln(3-MePyO)8I3.xH2O wherex = 0 for Ln = La and Tb,x = 1 for Ln = Pr, andx = 2 for Ln = Nd, Sm, Dy, Yb, and Y have been prepared and characterized by chemical analyses, conductance, infrared, proton nmr, and DTA data. Infrared and proton nmr data have been interpreted in terms of the coordination of the ligand to the metal ion through the oxygen of the N—O group. Proton nmr spectrum of the Yb(III) complex is indicative of a restricted rotation of the pyridine ring about the N—O bond.

ISSN:0008-4042    

DOI:10.1139/v76-451

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

In the thermal decomposition of methane at temperatures from 880 to 1103 K, hydrogen and ethane are the only primary products. The rate of formation of ethane falls rapidly towards zero as the reaction progresses until ethane reaches a steady-state concentration. This behaviour is interpreted in terms of a radical chain mechanism,Values ofk4were obtained which confirm the non-Arrhenius behaviour of this reaction at these temperatures. Similar chain sequences propagated by addition or abstraction reactions of methyl radicals with ethylene, propylene, and acetylene can account for the formation and disappearance of these secondary products.At a later stage in the pyrolysis a marked autocatalysis is observed and the yield of ethane increases sharply above its steady-state value. It is concluded that this autocatalysis is largely a homogeneous process and is not caused by or associated with carbon formation. Deposition of carbon on the surface was observed at a still later stage of the decomposition, and was quantitatively estimated by light absorption measurements. Possible mechanisms for the auto catalysis are discussed.

ISSN:0008-4042    

DOI:10.1139/v76-452

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The complexes (L—L)Fe2(CO)6react with a range of bidentate ligands to give the complexes (L—L)′(L—L)Fe2(CO)4((L—L) = fluorocarbon-bridged ligand such as f4fars, f4AsP etc. (L—L)′ = fluorocarbon- and hydrocarbon-bridged ligands such as f4AsP diars etc.). Spectroscopic studies, in particular magnetically perturbed Mössbauer measurements, indicate that (L—L)′ in most complexes is chelated to one iron atom, FeA. This leaves one CO group on FeAcisto the FeA—FeBbond and three on FeB. A smaller class of derivatives appear to have (L—L)′ bridging the two iron atomscisto the FeA—FeBbond. The sign ofVzzis positive at both iron sites in the bridged derivatives. It is negative at FeAand positive at FeBin the other complexes.

ISSN:0008-4042    

DOI:10.1139/v76-453

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

In this report, determination of unbound aquo iron species is accomplished by akinetic methodinvolving reaction with sulfosalicylic acid (SSA) on a time scale which is very short with respect to reaction of SSA with the glutathione complexes of iron. The data are used to calculate conditional binding constants for Fe(III) to glutathione. Binding constants in 0.1 Mionic strength media were obtained between pH 1 and 2.4 by the kinetic method, and near pH = 3 by spectrophotometryandby examination of the ratio of rate of complex formation and dissociation. The conditional binding 'constant'betweenpH 1 and 3 is represented as pK = −1.96 – 0.50pH. This is consistent with the importance of reactions involving only very limited proton release. Spectrophotometric data show that the —OH group on Fe(OH)2+is lost on glutathione complexing. Kinetics of the complex formation reaction between aquo iron(III) species and glutathione are slower than rates of reaction of iron(III) with simple ligands.The glutathione system is regarded as a model system important to natural water chemistry because it is a widely distributed biological sulfur-containing chelating agent.

ISSN:0008-4042    

DOI:10.1139/v76-454

出版商:NRC Research Press    

年代:1976

数据来源: NRC