摘要:

Crystals ofB-phenyl-dictychboroxazolidine are monoclinic,a = 8.4977(4),b = 9.0617(5),c = 7.0105(3) Å, β = 111.627(3)°,Z = 2, space groupP21. The structure was solved by direct methods and was refined by full-matrix least squares procedures to a finalRof 0.040 for 967 reflections withI ≥ 3σ(I). The bond lengths involving nonhydrogen atoms have been corrected for thermal motion. Bond lengths are: B—O, 1.460(3) and 1.474(3), B—N, 1.666(3), B—C, 1.613(3), C—O, 1.411(3) and 1.419(3), C—N, 1.485(3) and 1.486(3), C(sp3)—C(sp3), 1.514(4) and 1.524(4), C—C(ar), 1.384–1.400(4–6), mean C—H, 0.98(4), and N—H, 0.87(5) Å. The crystal structure consists of discrete molecules ofB-phenyl-diptychboroxazolidine each linked to two others by N—H … O hydrogen bonds (O … N = 2.914(3) Å) to form continuous spirals alongb.

ISSN:0008-4042    

DOI:10.1139/v75-193

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Rates of D2–ethanol exchange catalyzed by solutions of dichlorotris(triphenylphosphine) ruthenium(II) in 1:1 benzene–ethanol are reported as a function of the concentrations of ruthenium, deuterium, triphenylphosphine, and HCl. The rates were extremely fast, and approached 10−3 mol D2l−1s−1at 333 K with 1.3 mmol/l Ru. Over the temperature range 263 to 303 K, the apparent activation energy was 85 kJ/mol. The kinetics have been interpreted in terms of a mechanism in which activation of D2by RuCl2L3is rate-controlling. A comparison is made between the characteristics of this homogeneous catalyst and those of the related RhClL3.

ISSN:0008-4042    

DOI:10.1139/v75-194

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A general thermodynamic expression has been derived for the deviation Δ from Zdanovskii's rule. Conditions have been deduced under which Δ vanishes, and examples given. For nonzero values of Δ it has been shown by means of an example that Δ may be evaluated in some cases by the introduction of empirical assumptions, such as Harned's rule. The use of Zdanovskii's rule in facilitating the integration of the McKay–Perring equation has been discussed briefly.

ISSN:0008-4042    

DOI:10.1139/v75-195

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Raman spectra of aqueous solutions containing Cd2+and NO2−clearly reveal the presence of solvated nitrite ion and of complexes. A band at 861 cm−1is characteristic of the latter. The free nitrite concentration was measured from the intensity of the 817 cm−1line and the average ligand number was evaluated for solutions with composition prescribed by the mole-ratio method. Four cumulative formation constants were deduced: β1 = 61.6; β2 = 993; β3 = 2390; β4 = 1899. Evidence that nitrite chelates Cd2+through the two oxygen atoms is presented. The diagnostic spectral evidence consists of a high intensity, high frequency deformation mode and low intensity N—O stretching Raman bands with frequencies almost identical to those of the solvated nitrite ion. Data are also presented for solid Cd(NO2)2and Kx−2Cd(NO2)x(x = 3,4,5).

ISSN:0008-4042    

DOI:10.1139/v75-196

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Assignments for the13C chemical shifts of methyl aldopento- and hexofuranosides and of cyclopentane polyols are reported, and these chemical shifts are evaluated with respect to all combinations of configurational arrangements of the ring substituents. Acisconfiguration of vicinal substituents is generally associated with a substantial increase in shielding, as compared with thetransanalog. Among the furanosides, however, changes in configuration involving O-3 and C-5 are accompanied by a complex shielding pattern:e.g., effects on C-3 are minor, C-4 is more shielded incisthan intransisomers, and C-4 and C-5 of hexosides are more shielded than those of pentosides. Variations in shielding attributable tocisortransarrangements of substituents in a 1,3-relationship are encountered in only a few instances; however, it is noteworthy that C-4 islessshielded when O-l and O-3 arecisthan whentrans. These diverse effects are considered also in relation to steric interactions and to conformational influences on13C chemical shifts in the five-membered ring series.

ISSN:0008-4042    

DOI:10.1139/v75-197

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A novel chemical transformation is described in which chelocardin1, under normal ketalization conditions, is converted with elimination of the 2-acetyl group, to the bisdioxolane2. Hydrolysis of2yields 2-deacetylchelocardin4. The properties of the tricarbonylmethane system in1and of the 1,3-cyclohexanedione system in4are found to be profoundly modified by the presence of the 4-amino and the 12a-hydroxyl group.

ISSN:0008-4042    

DOI:10.1139/v75-198

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The pyrolyosis of CF3OOCF3(BTMP) was studied in the gas phase from 5 to 100 Torr BTMP pressure and between 197 and 244 °C in a clean nickel reactor by the static method. CF3O radicals, due to the initial splitwere scavenged by SO3F radicals producedin situby the thermal decomposition of their dimer S2O6F2. Under these conditions, CF3OOSO2F is the only product of BTMP pyrolysis, as shown by gas chromatographic analysis. Thus the BTMP pyrolysis becomes fully inhibited and the rate of accumulation of CF3OOSO2F is a measure ofk1. The rate constantk1turns out to be pressure-insensitive under the experimental conditions, from which it is inferred thatk1is actuallyk1∞, the limiting high-pressure unimolecular rate constant for reaction 1. Its temperature dependence yields the resultThis result is compared with other values of the O—O bond dissociation energy in BTMP. The experimental expression fork1 ∞is used to construct the pressure falloff ofk1following the procedure of Forst. The calculation confirms that falloff begins only below 10 Torr.

ISSN:0008-4042    

DOI:10.1139/v75-199

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The room temperature structure of Cd2(NH4)2(SO4)3(CAS), isotypic with the mineral langbeinite K2Mg2(SO4)3has been refined by full-matrix least squares methods. The structure is cubic witha = 10.362(7) Å and space groupP213. There are two inequivalent sites for the cation Cd2+and e.p.r. spectra of doped Mn2+show that Cd2+was substituted in both sites with preferential occupancy by Mn2+in a 1:3 ratio. Refinement of X-ray data on a mixed crystal of the stoichiometry Cd0.84Mn1.16(NH4)2(SO4)3shows that site I contains 82% Mn2+while site II has 38%. The zero-field splitting parameterDwas calculated for Mn2+in two sites using a point-charge model and confirms that Mn2+substitutes into site I with greater preference. Although a monoclinic ferroelectric phase of CAS has been suggested below 90 K, no change in space group symmetry could be detected at 80 K. The proton second moment, calculated by the van Vleck's formula, and compared with the experimental values, suggests a tunneling motion of the protons among the four vertices of the ammonium tetrahedron.

ISSN:0008-4042    

DOI:10.1139/v75-200

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Pyridazine was photolyzed with long wave ultraviolet radiation (3650–3663 Å) over the temperature range 100–160 °C. Nitrogen and vinylacetylene were the main products, their quantum yields at 110 °C being 0.12 ± 0.05 and 0.09 ± 0.04, respectively. Nitrogen formation is not significantly inhibited by the presence of oxygen and no isomerization ofcis-but-2-ene was observed during photolyses. It appears that some reaction occurs from the excited singlet, S (n → π*) A, but this state is efficiently deactivated photophysically. It is suggested that vinylacetylene is formed from a C4H4diradical by means of a 1,3 H-atom migration, and isotope effects observed for the photolysis of pyridazine-d4support C—H bond fission.

ISSN:0008-4042    

DOI:10.1139/v75-201

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The effect of change of solvent on the positions and intensities of absorption bands of some aromatic amines between 200 and 400 nm has been examined. In particular, the behavior of the band at 280 nm has been studied.In hydroxylic solvents, this band is displaced towards shorter wavelengths, and the dipole moment in the excited state of the molecule is smaller than in the ground state. The opposite effects are found when nonhydroxylic solvents are used.The results show how the molecular structure is altered by charge transfer effects and can explain how different solvents affect photochemical oxidation processes.

ISSN:0008-4042    

DOI:10.1139/v75-202

出版商:NRC Research Press    

年代:1975

数据来源: NRC