摘要:

The preparation of two epimeric secondary cyclosteroid alcohols in the steroidal A-ring by an intramolecular 1,3-elimination of bromide with zinc–copper couple is described. Iso merization of theendo-cyclopropanol to theexo-cyclopropanol is shown to occur with either the couple or zinc acetate. Solvolysis of the cyclopropyl tosylates is discussed. Spectral data are recorded.

ISSN:0008-4042    

DOI:10.1139/v75-240

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Catalytic hydrogenation of 5α-cholestan-3-one was investigated to examine the factors influencing the selective formation of the axial 3α-ol and it has been found that the most satisfactory yield of 3α-ol is realized using Urushibara nickel A, the nickel catalyst treated by acid, in hydrocarbon solvents at lower temperatures under high pressure. Preparation of epicholestanol and epicholesterol by this method is described.

ISSN:0008-4042    

DOI:10.1139/v75-241

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A series of spiro[n.2]alkan-2-ones and their 6 and 7 oxa derivatives were subjected to acid catalysis. In the former series, products arising from hydroxyl(cyclopropyl)carbinyl cations are observed, while in the latter series epoxide oxygen protonation appears to be the dominant reaction pathway. A novel oxavinylcyclopropane rearrangement is reported.

ISSN:0008-4042    

DOI:10.1139/v75-242

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The13C n.m.r. spectra of nineNupharalkaloids: deoxynupharidine, 7-epideoxynupharidine, nupharidine, 7-epinupharidine, nupharolutine, 7-epinupharolutine, thiobinupharidine, thionu-phlutine B, and neothiobinupharidine, have been determined. Also examined were the spectra of five model compounds, 2,2,4,4-tetramethylthiolane, 3(a)-methyl-3(e)-methylthiomethylquinolizidine, 3(e)-methyl-3(a)-methylthiomethylquinolizidine, 3(e)-methylthio-3(a)-methylquinolizidine, and 3-methylfuran. This latter group of spectra were used to assist the chemical shift assignments of theNupharalkaloids. The most significant findings of this study are: (i) axial methyl and thiomethylene groups are shielded more than their equatorial counterparts in all cases; (ii) axial and equatorial hydroxyl groups substituted at C-7 of deoxynupharidine and 7-epideoxynupharidine give α-, β-, and γ-effects in ring B similar to those in carbocyclic systems but also produce small upfield shifts in ring A especially at the carbons α to nitrogen; (iii) the effect of a 3-furyl group located at C-4 appears to have nearly the same effect on quinolizidine ring carbons as a methyl group in the same position, the effects being shielding and deshielding at the various ring carbons; (iv)N-oxide formation results in α-, β-, γ-, and δ-shielding and deshielding effects consistent with the incorporation of an axial oxygen into atrans-fused system or the formation of acis-fused quinolizidineN-oxide; and (v) methylene or methyl groups attached to C-2 and C-4 of a thiolane, including that in the skeleton of the C30thiaspirane alkaloids, experience deshielding δ-effects.

ISSN:0008-4042    

DOI:10.1139/v75-243

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The determination of rate constants of reactions of the type Na + RX = NaX + R by the diffusion flame method is critically investigated, both theoretically and experimentally. More precise methods than those used heretofore are developed for calculating rate constants from experimental data,viz. evaluation of the effective nozzle radius, a generalization of the Heller criterion, an improvement in the theory of the visibility limit, and allowance for wall reaction and halide consumption. These methods were applied to previous data on the reaction Na + C2H5Cl as well as to new data on the reaction of sodium with CH3Cl, CH3Br, CH3I, and C2H5Br.

ISSN:0008-4042    

DOI:10.1139/v75-244

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The kinetics of the unimolecular isomerization reactionhave been studied. The ΔH≠values in kcal mol−1are 36.8 ± 2.0 (M = M′ = Mn ), 46.8 ± 0.5 (M = M′ = Re ), 39.2 ± 2.8 (M = Mn, M′ = Re ). The mechanism of the rearrangement is discussed.

ISSN:0008-4042    

DOI:10.1139/v75-245

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Based on an analysis of the observed crystal structures of the phases of anhydrous sodium pyrophosphate, a calculation of the configurational entropy change of the system between the ordered ambient-temperature phase and the disordered hexagonal phase above 600 °C has been carried out. The result is 0.2187R cal mol−1deg−1whereRis the gas constant.

ISSN:0008-4042    

DOI:10.1139/v75-246

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The direct photolyses of thietane, 3-ethyl-2-propylthietane, and 3-methylthietane in the vapor phase, in solution, and in glassy matrices at low temperatures have been examined. The effects of varying the photolysis wavelength, the temperature, the pressure and the phase of the substrate, and of adding inert thermalizers on the nature and yields of the various products have been measured. The results are interpreted in terms of initial C—S cleavage to give a 1,4-biradical which may, in the gas phase, decompose or ring close before complete equilibration of the various rotamers is achieved, or which may be thermalized in condensed media and trapped in glassy matrices at low temperature.

ISSN:0008-4042    

DOI:10.1139/v75-247

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

It is shown that entropy production appears to be a completely monotonic function of time for several chemical reactions or reaction sequences taking place in closed systems at constant temperature; however this monotonicity principle does not extend to autocatalytic or oscillatory processes. Where it occurs, the complete monotonicity of entropy production stems essentially from the completely monotonic behavior of the species number densities as functions of time in the evolution of the reaction.

ISSN:0008-4042    

DOI:10.1139/v75-248

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Certain properties of concentrated solutions of indium trichloride, ranging in strength from 9.889 to 0.4070 m, have been investigated. These properties are: density, molar volume, specific and equivalent conductance, degree of ionization, ionization constant, relative viscosity, activities, and activity coefficients of solvent water and of solute. Two interesting results emerge,viz., the specific conductance passes through a maximum at 3.5 m, and, if the ionization of indium chloride is treated as that of a binary electrolyte, the expression α2c/(1 − α) is constant within 10% over the range 6.267 to 0.7363 m(13.90 to 2.122N).

ISSN:0008-4042    

DOI:10.1139/v75-249

出版商:NRC Research Press    

年代:1975

数据来源: NRC