摘要:

Propagation and termination rate constants have been measured for autoxidation of benzyl phenyl ether, benzyl-t-butyl ether, isopropyl ether, and benzyl ether. In the case of isopropyl ether and benzyl ether, estimates have been made of inter- and intramolecular propagation rate constants. Reactivities of acyclic ethers towards thet-butylperoxy radical have been determined. Rate constants for autoxidation of cyclic and acylic ethers have been summarized and compared.

ISSN:0008-4042    

DOI:10.1139/v70-144

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Co3(AsO4)2, an analogue of the mineral xanthiosite, crystallizes in the monoclinic space groupP21/cwithZ = 4. The unit cell parameters area = 5.830(4) Å,b = 9.675(2) Å, andc = 10.34(2) Å with β = 93.42(5)°. The intensity of 2261 independent reflections were estimated either from integrated precession photographs or by direct measurement using a scintillation counter. The final value of the reliability index is 0.072 for a full matrix least-square refinement where all the atoms have anisotropic thermal parameters. The three independent cations are surrounded octahedrally by oxygen atoms with mean Co—O bond lengths of 2.12 Å and a range from 1.99 to 2.29 Å. One of the arsenate ions, AsO44−, is a nearly regular tetrahedron with a mean As—O bond length of 1.70 Å; while the second, with an angular irregularity primarily introduced by one oxygen atom, shows a mean As—O bond length of 1.69 Å. This structure consists of nearly hexagonally close packed layers of oxygen atoms normal to thebaxis repeating every four layers.

ISSN:0008-4042    

DOI:10.1139/v70-145

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The crystal structure of Mg2As2O7has been refined by full matrix least squares procedures using 587 observed reflections. The structure of Mg2As2O7is of the thortveitite type, as reported by Łukaszewicz, with space groupC2/mand unit cell dimensionsa = 6.567(2) Å,b = 8.524(4) Å,c = 4.739(1) Å, β = 103.8(1)°, andZ = 2. The As—O—As group in the anion appears to be linear but the central oxygen atom undergoes considerable disorder in the plane perpendicular to this group. The AsO bond distances uncorrected for thermal motion are 1.67 Å for the As—O(—As) bond and 1.66 and 1.65 Å for the terminal As—O bonds. The finalRvalue obtained is 0.088

ISSN:0008-4042    

DOI:10.1139/v70-146

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A broad-line fluorine magnetic resonance study of the solid addition compounds SF4•AsF5and IF7•AsF5shows that each has two types of chemically distinct fluorine in the ratios of 1:2 and 1:1, respectively. The fine structure and the second moments of the spectra are consistent with the ionic formulations SF3+AsF6−and IF6+AsF6−. Bond lengths in the iodine compound are discussed in relation to the observed second moment at liquid-nitrogen temperature and the calculated rigid-lattice second moment based on the detailed sodium-chloride-type crystal structure of Beaton. The chemical shifts of the fluorines in the three ionic species are measured relative to trifluoracetic acid and to HF. Reorientations of the ions in the solid state are discussed on the basis of the change in second moment with temperature for each compound. A very rough estimate of the anisotropy of chemical shift in IF6+AsF6−is made from the slope of the second moment vs. field-squared line at liquid-nitrogen temperature.

ISSN:0008-4042    

DOI:10.1139/v70-147

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The following physical properties of the acetic anhydride – acetone – carbon disulfide system have been investigated: congruent compositions, excess volumes, dielectric constants. For the system acetone – carbon disulfide, the excess volumes and the molar polarizations are much greater than those required by the mixture rule. From this we deduced that this system is very non-ideal and might, at a suitable temperature, form two layers; two liquid layers did indeed form at −73 °C, the upper critical solution temperature occurring somewhere between this temperature and 0 °C. We offer it as a general rule that, if the deviation from additivity of molar polarization is large and positive, two layers will form at a sufficiently low temperature, provided that solid phases do not intervene. This deduction becomes almost a certainty if large positive deviations from additivity of molar volume and large positive heats of mixing are also present.

ISSN:0008-4042    

DOI:10.1139/v70-148

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The volumes of activation for the aquation of Co(NH3)5Cl2+and Cr(NH3)5NCS2+in aqueous acidic solution (0.1 MHClO4) have been measured and found to be −7.5 ± 1 and −8.6 ± 1 ml/mole, respectively. These values are more consistent with an SN1 than an SN2 pathway for the aquation of both of these complexes.

ISSN:0008-4042    

DOI:10.1139/v70-149

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The thermal decomposition of cyclopentene, which had previously been shown to proceed by a gas-phase homogeneous process, has been found to be accelerated in the presence of glass wool fibers. The roles of products in the lowering of the overall rate in the later stages of decomposition have been investigated.

ISSN:0008-4042    

DOI:10.1139/v70-150

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The proton magnetic resonance spectra of cation-exchange resins of crosslinkage X1 to X16 in the H+, Li+, Na+, K+, Rb+, Cs+, and NH4+forms have been recorded and the values of the molal chemical shift, δM+0, are found to be −0.321, −0.005, 0.041, 0.031, 0.028, 0.015, and 0.00 (assumed) p.p.m./mole, respectively, for the cations. These values are very nearly equal to those observed in corresponding aqueous solutions, indicating that ion–solvent interactions are similar in both the resin matrix and the aqueous solution. The temperature dependence of the chemical shift shows the same trend. The effective hydration numbers calculated from the temperature dependence are 2.0 (4.81 m) for the H+form, 4.8 (3.25 m) and 3.6 (5.26 m) for the Na+form, 4.4 (3.9 m) for the K+form, and 2.4 (6.18 m) for the Cs+form. The ions in the resin phase behave as solutions of strong electrolyte, which is consistent with the polyelectrolyte gel model for the ion-exchange resin.

ISSN:0008-4042    

DOI:10.1139/v70-151

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The mercury 6(3P1) photosensitized decomposition of methyl vinyl ether has been studied in the vapor phase in a static system at 55 °C between 0.2 and 10.0 Torr. The principal products are propanal and ethane. It is concluded that the primary process involves the direct production of methyl and vinoxy radicals with no more than 3% participation of a competing step producing ethylene. Neither carbon–hydrogen bond breaking nor the production of primary excited molecules is observed.

ISSN:0008-4042    

DOI:10.1139/v70-152

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

This paper attempts to obtain agreement between theoretical and experimental supersonic molecular beam intensities. Measurements of absolute beam intensities are presented, corrected for the effect of background scattering in the expansion chamber. It is found that these intensities are considerably lower than those predicted by existing theories. This is true even when losses due to imperfect skimming are negligible. A new mechanism is therefore proposed which postulates a considerable attenuation of the beam due to "self-scattering" collisions upstream of the skimmer and downstream of the onset of translational freezing. Using this mechanism it is possible to reasonably reproduce the experimental intensities.

ISSN:0008-4042    

DOI:10.1139/v70-153

出版商:NRC Research Press    

年代:1970

数据来源: NRC