摘要:

The gas phase X-ray photoelectron spectra, XPS, were observed for the series C6F5X (X = F, Cl, I, Br, H). Binding energies were determined from the spectra using the ESCAPLOT Program. Charge calculations were carried out using Equalization of Electronegativity, CNDO/2, and ACHARGE approaches on each molecule. The more sophisticated analysis leads to the following equation correlating the (C 1s) binding energies and the atomic chargesqi

ISSN:0008-4042    

DOI:10.1139/v77-177

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

'Number-time' data obtained during studies on the nucleation from aqueous solution of CaSO4•2H2O (gypsum) using the droplet technique and a variable driving force are reported. Sulfate ion was generated,in situ, by the reaction between S2O82−and S2O32−in the presence of Ca2+. The rate of the reaction was determined from polarographic data. The stoichiometry and solubility of the precipitate in the aqueous matrix were determined.Problems which arise during analysis of 'number-time' data obtained from droplet experiments with a large spread in individual droplet volumes and a variable driving force using techniques suggested in the literature are commented upon. A new technique was developed and applied to the analysis of our data. The effects of a non-steady state rate of nucleation, variable lag times and a decreasing cation: anion ratio on the derived results are discussed.

ISSN:0008-4042    

DOI:10.1139/v77-178

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The dielectric properties of phenol I have been measured as isothermal functions of pressure between 140 and 1520 bar and between +35 and −10 °C. No dielectric relaxation was observed. The static (50 kHz) permittivity at 10 °C is given with a precision of 0.3% bywherePis in bar. The extrapolated value at 1 bar is 2.882 ± 0.009 which compares with literature values between 2.74 and 2.84. The 50 kHz molar polarization,, at 10 °C is given bywhereVandVoare the molar volumes at pressuresPand 1 bar, respectively. At 10 °C and 1 bar, the electronic and atomic polarizations are estimated to be 26.9 ± 0.3 cm3and 5.1 ± 0.4 cm3, respectively. Expressions for the isobaric temperature dependence of ϵo′ are reported for several pressures. Below 1500 bar, (∂ϵo′/∂T)Pis negative, as expected from the density change but in contrast with previous results and with results obtained while varying the temperature under a constant applied pressure of 1 kbar. The accuracy of the temperature dependence at 1 bar is not high, judging from the thermal expansivity calculated from it.ϵo′ of phenol II at 10 °C and an estimated pressure of 2000 bar is 3.10 ± 0.06, with the corresponding molar polarization 30.75 ± 0.5 cm3. No intrinsic dielectric relaxation was observed in phenol II and the molar polarization shows no marked discontinuity at the transition. Phenol II is, therefore, like phenol I, a hydrogen-bonded solid in which the hydroxyl hydrogen atoms are ordered, either fully or in chains. The dielectric parameters and Arrhenius activation energies of two transient dispersions which appeared whenever phenol II formed are discussed.

ISSN:0008-4042    

DOI:10.1139/v77-179

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Spin–lattice relaxation times of1H, D, and199Hg have been measured between 234 and 333 K in liquid dimethylmercury and its isotopic modifications. These measurements have allowed the relaxation mechanisms to be separated. It was found that the spin–rotation interaction is the dominating mechanism for the199Hg relaxation at 14.1 kG even at low temperatures. We have estimated the spin–rotation constants,along with the chemical shift anisotropyIt is concluded that reorientation about the symmetry axis is not well described by molecular diffusion. Reorientation of the methyl group about its symmetry axis is found to be approximately forty times faster than the reorientation about the perpendicular axis.

ISSN:0008-4042    

DOI:10.1139/v77-180

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Values of ΔCP≠have been obtained for the hydrolysis of 1- and 2-adamantyl nitrate in water and of 1-adamantyl nitrate in 0.2 mol fraction ethanol–water and acetonitrile–water. The limiting value of ΔCP≠for displacement of the NO3−ions in water is more negative than −130 cal mol−1deg−1. Much less negative values in mixed solvents show that the large negative values obtained for hydrolysis in water derive in some manner from the structural properties of water. The mechanistic implications of these facts are discussed.

ISSN:0008-4042    

DOI:10.1139/v77-181

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The empirical 'm' values from the Grunwald–Winstein solvent correlation equation for SNdisplacement reactions show a fair correlation with corresponding ΔCP≠values obtained from hydrolysis in water. The correlation plots separate according to the nature of the displaced groups, a consequence of different relative effects of anions on water structure. The mechanistic significance of the correlation is examined.

ISSN:0008-4042    

DOI:10.1139/v77-182

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Various methods of substituting 1,3-dihydroxyanthraquinones in the 2-position were investigated. It was eventually found that direct hydroxyalkylation in the presence of definite amounts of sodium bicarbonate could be carried out. The reaction of 1,3,6,8-tetrahydroxyanthraquinone with 5-oxohexanal or 4-hydroxybutanal gave, respectively, among other products, (±)-averufin and (±)-bipolarin.

ISSN:0008-4042    

DOI:10.1139/v77-183

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The reflection method is used to calculate energy shifts and linewidths in predissociation by a linear continuum. The analytic results of this method are compared to the exact analytic calculations. It is found that, as in semiclassical calculations, energy shifts and linewidths usually vanish at the same energies. The spectroscopic implications of this finding are pointed out.

ISSN:0008-4042    

DOI:10.1139/v77-184

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Six 3-substituted picolinic acids were synthesized and decarboxylated in buffered aqueous solutions of ionic strength 1.0 at 150 and/or 95 °C. 3-Amino- and 3-hydroxypicolinic acids appear to decarboxylate by initial protonation, but the others fit the requirements of the Hammick mechanism for picolinic acid decarboxylation. Both electron-withdrawing and electron-releasing 3-substituents accelerate decarboxylation in picolinic acids but inhibit decarboxylation in their anions. Acceleration in the acids is considered to be the result of interference by 3-substituents with coplanarity of the carboxyl group and the aromatic nucleus. This reduces the order of the bond between the carboxyl group and the ring, thus facilitating bond breaking. In decarboxylation of the anions water appears to play a critical role, since picolinate ions have not been observed to decarboxylate in any other solvent, including ethylene glycol. It is proposed that water forms a hydrogen-bonded bridge between carboxylate oxygen and aromatic nitrogen, so that as the carbon–carbon bond breaks a nitrogen–hydrogen bond is formed. This may provide a lower energy path through an ylide intermediate than would be required if the picolinate ion were to decarboxylate to a 2-pyridyl carbanion.

ISSN:0008-4042    

DOI:10.1139/v77-185

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Starting from methyl 3,6-dideoxy-3-nitro-α-D-glucopyranoside (1) and proceeding through its 4-mesylate (2) and 2,4-dimesylate (3), respectively, methyl 3,4,6-trideoxy-3-nitro-α-D-xylo-hexopyranoside (4) and methyl 2-O-acetyl-3,4,6-trideoxy-3-nitro-α-D-threo-hex-3-enopyrano-side (5) were prepared. The 4,6-O-benzylidene derivatives (6,8, and10) of methyl 2-O-acetyl-3-deoxy-3-nitro-β-D-glucopyranoside, methyl 3-deoxy-3-nitro-α-D-glucopyranoside, and methyl 2,3-dideoxy-3-nitro-α-D-arabino-hexopyranoside were found to undergo without difficulty the Hanessian–Hullar reaction withN-bromosuccinimide, to give good yields of the corresponding 6-bromo-4-benzoates (7,9, and11). Partial anomerization giving the β-anomer12of11was observed under certain circumstances.

ISSN:0008-4042    

DOI:10.1139/v77-186

出版商:NRC Research Press    

年代:1977

数据来源: NRC