摘要:

The possible occurrence in bulk relaxation of pure-exponential, near-exponential, and non-exponential decay of the total energy is examined in terms of the normal-mode and information-theoretic approaches. Experimental tests are suggested for the identification of pure-exponential decay caused by adherence to the 'sum rule', and of near-exponential decay. In the case of near-exponential decay (as opposed to pure-exponential decay), it is not possible to derive reliable state-to-state rate constants by invoking approximate adherence to the sum rule.

ISSN:0008-4042    

DOI:10.1139/v77-102

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The title compound has been prepared by the reaction of SbF5and SbCl5in liquid SO2. Raman and Mössbauer spectra have been recorded and its crystal structure determined by three-dimensional X-ray counter measurements. Crystals are monoclinic witha = 12.359(6) Å,b = 16.480(10) Å,c = 9.387(3) Å, β = 103.96(5)°. The structure has been refined in the space groupP21/nto a final agreement indexR2of 0.113 for 2415 independent reflections. The structure consists of acisfluorine-bridged trimer with one of the chlorine atoms 25% substituted by fluorine.

ISSN:0008-4042    

DOI:10.1139/v77-103

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Flash photolysis of I2in a large excess of O2was studied between 300 and 1173 K. Between 573 and 1173 K the rate of atomic recombinationwas measured without interference of side reactions. Its rate constant was found to be. Between 573 and 873 K there is an induction period lasting several hundred microseconds during which only a small net change in the iodine molecule concentration takes place. This induction period is consistent with the reactionBeow 573 K, the overall recombination rate constant has a temperature dependent negative temperature coefficient and is enhanced when the flash includes radiation in the neighborhood of 200 nm. Evidently this occurs because the flash photolysis of O2creates new efficient third bodies, such as O3and O2(1Δg), which accelerate the recombination reaction either directly or via an IO intermediate. The mechanism for the formation of IO during the flash photolysis of I2in an excess of O2was studied. It was shown that the reactions O(3P) or, where O3* refers to an electronically or vibrationally excited state of O3, account for the formation of IO under our experimental conditions. IO may also possibly be formed via the reaction. On the other hand, reactions between excited or ground state I atoms and O2suggested by earlier workers do not occur. Thus, all experimental complications observed are traceable to the presence of O2photolysis products and to the reaction of I(2P1/2) with O2(3Σg−).

ISSN:0008-4042    

DOI:10.1139/v77-104

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Two methods are described for the preparation of substituted cyclopropanediols: reduction of β-diketones, and bridging of 1,2-bissiloxyalkenes; a number of the latter compounds were prepared by a new method. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v77-105

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The redox properties of 2,3,7,8-tetramethoxyselenanthrene and 2,3,7,8-tetramethoxythianthrene have been studied in solution in order to compare their potential applicability as charge-transfer donors. The selenium compound is the weaker reductant, yielding a stable radical cation and a reactive dication, the former dimerizing in solution. Electron spin resonance and visible absorption spectra of the stable species were obtained. The 1:1 charge-transfer complexes of the above donors with tetracyanoquinodimethane are found to be insulators.

ISSN:0008-4042    

DOI:10.1139/v77-106

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The conformations of saturated hydrocarbon chains are analysed by a least-squares fit of calculated to observed time-averaged carbon-13 chemical shifts. The calculated resonances are the sums of products of conformer resonances and conformer probabilities. The conformer shieldings are derived with predictive parameters developed earlier for conformationally well defined systems. The conformer probabilities are taken to be products of rotamer probabilities. The rotamer probabilities are variables in the analysis.

ISSN:0008-4042    

DOI:10.1139/v77-107

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

4,4′-Bis(dicyanomethylene)bicyclohexylidine and its dihydro derivative, 4,4′-bis(dicyanomethylene)bicyclohexyl were prepared from the condensation of malononitrile with the corresponding diketone. Bicyclohexylidene-4,4′-dione was synthesized from the monoketal of cyclohexanedione via the symmetric azosulfide.The uv spectra of the 4,4′-bis(dicyanomethylene)bicyclohexylidine and related model compounds indicate the presence of a long range interaction between the dicyanomethylene groups of the title compound.

ISSN:0008-4042    

DOI:10.1139/v77-108

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

An outline of a synthetic route to the antibiotic resistomycin is presented. We report the successful construction of an intermediate containing all of the carbon atoms in resistomycin with requisite functionalities. The key steps involved an aldol type condensation of the dianion from 2,4,6-trimethoxybenzoylacetone and a suitable acetophenone. This was followed by a novel acid-catalyzed cyclization–condensation to form the naphthalene intermediate required in our scheme.

ISSN:0008-4042    

DOI:10.1139/v77-109

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The solvent effect on the iodide–triiodide equilibrium has been investigated by means of calorimetric and potentiometric measurements. The aprotic solvents studied were nitromethane, nitrobenzene, sulfolane, acetonitrile, propylene carbonate, acetophenone, dimethylformamide, dimethylsulfoxide, ando-dichlorobenzene. The resulting enthalpy and free energy changes imply that the variations of the enthalpies and free energies of transfer of the iodide and triiodide ions probably are small and that there is an important non-coulombic contribution to these transfer parameters. Values were obtained for the enthalpy of formation of two solid triiodides, which together with values for other triiodides, cast doubt on reported calculated lattice enthalpies of triiodides and formation enthalpy of I3−ion in the gas phase. This latter formation enthalpy is found to be, from our solution data, more negative than −22 kcal mol−1.

ISSN:0008-4042    

DOI:10.1139/v77-110

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The shift in the temperature of maximum density for aqueous solutions customarily has been dissected into anidealand astructuralcontribution. This analysis demonstrates that the dissection leads to the formulation of anidealstate which is attained by a fortuitous superposition of temperature dependent properties of pure components and, hence, cannot serve as a reliable reference state for comparing the influence of different solutes upon solution structure.

ISSN:0008-4042    

DOI:10.1139/v77-111

出版商:NRC Research Press    

年代:1977

数据来源: NRC