摘要:

Enrichment of helium–argon gas mixtures by accommodation pumping in a 10-stage pump is described. With the warm half of the pump at room temperature, pumping ratios are reported for cold surfaces at 77, 195, and 273 °K.

ISSN:0008-4042    

DOI:10.1139/v72-149

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Radiochemical reactions of82Br,128I, and56Mn have been studied in neutron-irradiated BrMn(CO)5and IMn(CO)5. The parent compounds were found to contain 49 and 28% of the82Br and128I, but only 6 and 10% of the56Mn, respectively. The dimeric [XMn(CO)4]2accounted for 28% of the82Br, but only about 2% of the56Mn. Some56Mn2(CO)10was also found. The radiochemical yields of several products were found to increase substantially on thermal treatment of the target material.Reaction pathways are suggested which can account for the thermal effects, which involve halogen atom transfer and carbonyl transfer in the solid.

ISSN:0008-4042    

DOI:10.1139/v72-150

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The pyrolysis of trimethylantimony has been studied in a toluene carrier flow system over the temperature range 690–803 °K (total pressures 3.6–173.4 mm, contact times 1.0–13.5 s, decomposition 3.9–89.5%). The progress of the reaction was followed by measuring the amount of methane, ethane, and ethylbenzene formed. In 23 runs the undecomposed alkyl was also determined. The quantity found was in agreement with that expected from the product analysis if three methyl radicals are released for each molecule undergoing reaction. No heterogeneous reaction was detected.Deuterium labeling led to the conclusion that regeneration of the parent alkyl occurred during the course of the decomposition. This regeneration reaction was effectively eliminated by working at toluene pressures above 150 mm. Least squares analysis of the results obtained under conditions where regeneration should not be important givenLog10k/s−1 = 15.33 − (55 900 ± 1 000)/2.3RTThe activation energy should be a good approximation toD[(CH3)2Sb—CH3].Significant decomposition of SbCH3probably does not occur. It seems most likely that free Sb is formed via 2Sb(CH3) → Sb(CH3)2 + Sb.

ISSN:0008-4042    

DOI:10.1139/v72-151

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The kinetics of the thermal insertion reaction of SnCl2with the metal–metal bonded complex (π-C5H5)2Fe2(CO)3P(OC6H5)3have been studied by following the change in the visible spectrum in THF over the temperature range 40.0 to 55.0 °C. The data are consistent with a two-stage mechanism involving the formation of an intermediate in which the iron–iron bond has been broken but the carbonyl bridges are left intact. From the activation enthalpy of 23.4 ± 0.5 kcal/mol for the formation of the intermediate it is concluded that the triphenyl phosphite has brought about a weakening of the iron–iron bond.

ISSN:0008-4042    

DOI:10.1139/v72-152

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Hg(SCN)2crystals belong to the monoclinic space groupC2/mwitha = 10.878 Å,b = 4.042 Å,c = 6.435 Å, β = 95.28°, andZ = 2. The structure was solved by the Patterson method and refined on 217 independent observed reflections to aRfactor of 0.032. All the atoms are found on the planes of symmetry of the unit cell with mercury occupying centrosymmetric positions and forming collinear Hg—S bonds to two coplanar SCN groups. An octahedral environment is achieved through weak interaction of mercury with the nitrogen atoms on four neighboring molecules.

ISSN:0008-4042    

DOI:10.1139/v72-153

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Secondary kinetic deuterium isotope effects are presented for the reaction of methyl-d3iodide and pyridine in four different solvents. Calculations on mass and moment of inertia change with deuteration in the initial state and an assumed tetrahedral transition state, together with internal rotational effects, are used to rationalize the inverse isotope effects. It is concluded from the variation of the isotopic rate ratio, that the transition state structure varies with solvent.

ISSN:0008-4042    

DOI:10.1139/v72-154

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A survey of kinetic, secondary deuterium isotope effects, for α, β, and γ deuterated alkyl halides reacting with pyridine in nitrobenzene solvent has been made. α-Deuterium effects have been measured for eight compounds, β-deuterium effects for four compounds, and one rate ratio for γ-deuteration is reported. The possible errors in the rate ratios for β-deuterated compounds, resulting from the elimination side reaction have been determined. The results are discussed in terms of transition state structure.

ISSN:0008-4042    

DOI:10.1139/v72-155

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Kinetics of the thermal decomposition of pure formaldehyde were studied over a temperature range of 466–516 °C and a pressure range of ~ 50–160 Torr. Arrhenius parameters and rate laws were determined for carbon monoxide, hydrogen and methanol as follows:A mechanism is postulated which is qualitatively consistent with the experimental results but the activation energy for reaction 1is ~15 kcal/mol lower than predicted from recent thermochemical data, suggesting the possibility of a heterogeneous reaction.

ISSN:0008-4042    

DOI:10.1139/v72-156

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Reactions of Cu(I)Cl, Cu(II)Cl2, Cu(II) acetylacetonates, and Cu(II)N-methylsalicylalidiiminate with the stable free radical 2,2-diphenyl-1-picrylhydrazyl have been investigated. In all cases Cu(II) was reduced and the organic radical behaved as an electron donor-ligand to form complexes containing Cu(I). These novel free radical Cu(I) complexes were characterized by various spectroscopic methods, including e.s.r.

ISSN:0008-4042    

DOI:10.1139/v72-157

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The conformational analysis of the ethylenediamine molecule has been studied by the LCAO-EHMO calculation method. The results indicate that the most stable conformation of the molecule is thegaucheform, in which the angle N—C—C—N isca. 63.0° measured from thecisform. This is in agreement with experimental data and can explain the fact that the ethylenediamine in its chelate complexes is always in thegaucheform. In addition, the present results indicate that thetransform is the next most stable conformation of ethylenediamine in agreement with experimental results on bridging ethylenediamine metal complexes.

ISSN:0008-4042    

DOI:10.1139/v72-158

出版商:NRC Research Press    

年代:1972

数据来源: NRC