摘要:

Fluorine resonance spectroscopy has been used to calculate stoichiometry and equilibrium constants for formation of 1:1 and 2:1 complexes between dimethyl sulfide and tungsten hexafluoride at several temperatures. The 2:1 complex has fine structure from spin–spin coupling at very low temperature, but the simplicity of the spectra prevent detailed mechanistic studies. Many other Lewis base complexes of tungsten and molybdenum hexafluorides have been prepared.

ISSN:0008-4042    

DOI:10.1139/v76-334

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Independent formation cross sections in the fission of238U by protons of energy 20–85 MeV were obtained for the nuclides111Ag,112Ag,117In,115In,111Pd, and115Cd. The last three mentioned were estimated on the basis of measurements and isomeric yield data. Charge dispersion curves were constructed andZp, the most probable charge, determined. The values for (ZA − Zp) lie intermediate between those measured for fission products of higher and lower mass. The number of neutrons emitted was estimated and found to be higher than in asymmetric fission, leading to the conclusion that the former are events arising from higher deposition energies.

ISSN:0008-4042    

DOI:10.1139/v76-335

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Arrhenius parameters have been measured for hydrogen abstraction by C2F5radicals (produced from the photolysis of perfluoropropionic anhydride) from methylfluorosilanes and tetramethylsilane.The results are discussed in relation to those of similar reactions involving the CF3and the CH3radical, and interpreted in terms of polar effects.

ISSN:0008-4042    

DOI:10.1139/v76-336

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Epimeric mixtures of juvabiol (3a) and isojuvabiol (4a) have been detected in six North AmericanAbies balsamea(L.) Mill. trees and isolated from the whole-wood extract of three. These juvabione related alcohols are insect juvenile hormone analogues with selective action typical of juvabione (1) and Δ4′-dehydrojuvabione (2). The widespread occurrence of these alcohols indicates that the original 'paper factor'was notdue to1alone, nor was it due to a mixture of1and2. In addition a fifth IJHA with selective action, Δ3′-dehydrojuvabi-5′-ol (5), was detected in the hot ethanol extract of four trees and isolated from one tree. It is shown that5is an allylic rearrangement product of the Δ4′-dehydrojuvabiols6aand7a. Mixtures of campesterol and sitosterol are the major crystalline components present in all the petroleum ether soluble extracts.

ISSN:0008-4042    

DOI:10.1139/v76-337

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

This paper examines, in terms of the normal-mode analysis developed earlier (Part I), the nature of relaxations in which a diatomic gas, highly diluted in a heat bath of inert gas atoms, is subjected to a sudden change as in shock-wave excitation or laser schlieren experiments.It is shown in detail how the observed relaxation time in a shock-wave excitationto a fixed final temperaturedepends on the initial temperature. At the same time, it is confirmed that the characterisation as 'mainly rotational' of the measured relaxation time in H2when it is heated from room temperature to 1500 K in a shock wave is perfectly plausible.On the other hand, the calculations show that in laser schlieren experiments in which thev = 1,J = 1 level of H2is overpopulated, the vibrational relaxation time of H2at the temperature in question is recovered, although interesting effects should appear if otherJlevels were populated initially, or if the experiments were carried out at much higher ambient temperatures.The calculations also demonstrate that it is not generally possible to derive relaxation times by following the variation in population of any particular level of the molecule: multiple overshoots sometimes occur, and apparent relaxation times both longer or shorter than the true relaxation times could often result from attempts to follow level populations as a function of time.

ISSN:0008-4042    

DOI:10.1139/v76-338

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The thermal isomerisation of methyl isocyanide has been measured in the rigorous absence of self-heating over a temperature range from 120–320 °C and at pressures from 2–100 torr. Expressions are given for the rate constant as functions of both temperature and pressure in these ranges of the two variables. The infinite-pressure rate constant is accurately represented by an Arrhenius line with no curvature havingE∞ = 38.2 ± 0.2 kcal mol−1and log10A∞(s−1) = 13.35 ± 0.11, although at all other pressures,Eis a function of temperature.

ISSN:0008-4042    

DOI:10.1139/v76-339

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Model compounds of Δ4,5-, Δ5,6-, and Δ6,7-alkenylnitrosamines were synthesized and photolyzed to generate the corresponding alkenylaminium radicals. The Δ5,6-alkenylaminium radicals underwent efficient intramolecular addition leading to the exclusive formation of pyrrolidine derivatives, the yield of which was lower if the steric strain and hindrance were severe in the cyclization transition state. The Δ6,7-alkenylaminium radical cyclized inefficiently to piperidine derivatives and the Δ4,5-alkenylaminium radicals did not appear to cyclize; in both cases other pathways having lower activation energies, such as elimination and hydrogen abstraction, predominated. Evidence that the direction of cyclization is controlled by the degree ofp-orbital overlap, but not by stability of the developing products, in the transition state is presented. The stereochemical factors associated with the overlap determined the yields of the cyclization products. This is in excellent agreement with the fact that the transition state of cyclization is reached at an early stage in the reaction coordinate. Metal ion catalyzed or radical initiated decomposition of some alkenyl chloramines were found either to cyclize to a mixture of pyrrolidine and piperidine derivatives or to undergo no cyclization.

ISSN:0008-4042    

DOI:10.1139/v76-340

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

1-Bromo-3,4-dimethyl-3-phospholene quaternizes readily with functional organic halides Z—(CH2)n—X with Z = OR, SR, C(O)R, CH(OR)2, COOR, CONR2, CN,n = 1 or 2, and X = Cl or Br. The adducts thus obtained are formally related to the diene-dihalophosphine McCormack cycloadducts. When reacting with H2O or H2S they yield the corresponding P-functional phospholene oxides or sulfides. Phospholes are also obtained by reaction with DBU whenn = 1 and Z = OR, SR, or whenn = 2 and Z = CN. Some chemical properties of these new compounds are described and pmr data are given.

ISSN:0008-4042    

DOI:10.1139/v76-341

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Routes to 6-deoxy-hex-2-enopyranosides and the corresponding 4-ulo derivatives have been investigated. The route (Scheme 2) beginning with the readily prepared ethyl 2,3-dideoxy-α-D-erythro-hex-2-enopyranoside is preferred, and the steps involve selective tosylation, iodinolysis, and reduction with Raney nickel. During the iodinolysis step a rearrangement occurs leading to furan derivatives. However, tliis is suppressed completely by the addition of pyridine to the iodinolysis medium. If the 4-ulo derivative is the desired substance, the most direct route (Scheme 3) utilises the well-known 2,3-dideoxy-hex-2-enopyranosid-4-ulose, the primary hydroxyl group being removed in two simple steps.

ISSN:0008-4042    

DOI:10.1139/v76-342

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The reaction of 1-octene with the lead tetraacetate–hydrogen fluoride reagent led to products resulting from the Markovnikov addition of lead and its ligand (fluoro or acetoxy) to the olefinic double bond. Displacement of lead from the organometalic intermediate via three separate pathways could be distinguished; displacement concomitant with hydride migration alkyl migration, or direct displacement by an external ligand. The pathways for the formation of the product difluorides, fluoroacetates, and diacetate could be followed by an analysis of the products obtained from carrying out the reaction using 1-octene-1-13Cas substrate. The major pathways to product formation resulting from either hydride or alkyl migration could be rationalized as proceeding through the intermediacy of a resonance stabilized α-fluorocarbonium ion.

ISSN:0008-4042    

DOI:10.1139/v76-343

出版商:NRC Research Press    

年代:1976

数据来源: NRC