摘要:

Chromatographic separation of the complexescis- andtrans-Co(en)2(S2O3)2−,cis- andtrans-Co(en)2(SO3)2−,cis- andtrans-Co(en)2Cl2+,cis-Co(en)2(N3)2+,cis-Co(en)2(SO3)(N3)0, Co(en)2(S2O3)(N3)0, and Co(en)2(S2O3)(OH2)+(en = ethylenediamine) was carried out by high-performance liquid chromatography. Good separations were achieved on a μ-Bondapak C18reversed-phase octadecyldimethylsilane (ODS) column using tributylmethylammonium cations and octylsulphonate anions. The efficiency and speed of the separations were superior to those obtained on a Partisil SCX ion exchange column.

ISSN:0008-4042    

DOI:10.1139/v86-322

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The concept of minimum rate constants,k(E)min, for unimolecular decompositions does not, according to the quasi equilibrium theory (QET), provide a rationalisation of the occurrence of the higher energy reaction, loss of methyl, rather than the more favorable process, loss of methane, from metastable butanone and 3-methylbutanone molecular ions.

ISSN:0008-4042    

DOI:10.1139/v86-323

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Standard potentials (E0) of the Ag–AgCl electrode have been determined in 1, 2, and 4 mNaNO3 + water mixtures at five equidistant temperatures ranging from 15–35 °C from the emf measurements of the cell: Pt, H2(g, 1 atm)/HCl (m) NaNO3 +water/AgCl–Ag. These values have been used to evaluate the transfer energeticsaccompanying the transfer of 1 mole of HCl from the standard state in water to the standard state in each of the NaNO3 + water mixtures. Transfer free energiesof HCl and that of the individual ions obtained from a separate study, and those obtained after correcting the "cavity effect" and Born-type electrostatic effect, as estimated tentatively by the scaled-particle theory (SPT) and simple Born equation respectively, have been discussed in the light of ion–ion–solvent interactions. The observed–composition profile as well as that obtained after correcting for the "cavity effect" were examined in the light of semiquantitative theory proposed by Kunduetal. earlier and are found to substantiate this theory.

ISSN:0008-4042    

DOI:10.1139/v86-324

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Densities, refractive indices, viscosities, enthalpies, vapour–liquid equilibria, and surface tensions were determined for the n-pentane + dichloromethane system at 298.15 K. From the experimental results, excess molar volumes, excess viscosities, excess molar enthalpies, excess molar Gibbs free energies, and excess surface tensions were calculated. From these data, qualitative information could be obtained about the interaction between both chemical species.

ISSN:0008-4042    

DOI:10.1139/v86-325

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Thermal decomposition of ethyl azidoformate in excess of dimethyl terephthalate (DMT) (1) in acetic anhydride as solvent results in the formation ofN,N-dicarbethoxy-4,8-dicarbomethoxy-2,6-diazabicyclo[3.3.0]octa-3,7-diene (3) in addition toN-carbethoxy-2,5-dicarbomethoxy-1H-azepine (2) and ethylN-(2,5-dicarbomethoxyphenyl)carbamate (4). The structure of the diazabicyclooctadiene (3) was established on the basis of spectral, elemental, and X-ray crystallographic analyses.

ISSN:0008-4042    

DOI:10.1139/v86-326

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The products of the reaction ofcis-[Pt(EMSO)2Cl2] (EMSO = ethylmethylsulfoxide) with Ag2SO4were studied by195Pt nuclear magnetic resonance. The results have shown the presence of several species in aqueous solution. The reactions were done at different conditions of pH. The spectra of two isolated oligomers were also measured. The hydroxy-bridged dimer and trimer show a signal around −2900 ppm while the hydrolyzed monomers have signals around −3200 ppm. A semi-quantitative profile of the different equilibria in solution is suggested.

ISSN:0008-4042    

DOI:10.1139/v86-327

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The evolution of ion species by unimolecular and bimolecular reactions, both concurrent and sequential, has been investigated for each of 2-propanone,d6-2-propanone, 4-hydroxy-4-methyl-2-pentanone, and 4-methyl-3-penten-2-one. Infrared multiphoton dissociation (IRMPD) has been used in order to differentiate between gaseous ionic isomers. It is concluded that the isomeric species, protonated 2-propanone dimer and protonated 4-hydroxy-4-methyl-2-pentanone, both ofm/z117, are of different structures. The ion species C6H11O+ofm/z99, and its perdeuterated analogue, which is observed in all three systems, may exist in two forms, one of which is unique to 2-propanone while an alternative form appears to be common to 4-hydroxy-4-methyl-2-pentanone and 4-methyl-3-penten-2-one. The ion species ofm/z 83 (C5H7O+) which is observed only in the latter two systems only could not be differentiated and may have a common structure. In the protonated dimers of 2-propanone and 4-hydroxy-4-methyl-2-pentanone, evidence obtained by IRMPD indicates that the activation energy for dedimerization (134 kJ mol−1) is less than that for the dehydration process.

ISSN:0008-4042    

DOI:10.1139/v86-328

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The Claisen rearrangement of 1,4-bis(m-methoxyphenoxy-)2-butyne (1b) gives four isomeric dimethoxy-6H-benzofuro[3,2-c]-6a,11a-dihydro-11a-methylbenzopyrans (3), three dimethoxy-4b,9b-dihydro-4b,9b-dimethylbenzofuro[3,2-b]benzofurans (4), and, in the presence of acid, three dimethoxy-5a,10b-dihydro-5a,10b-dimethylbenzofuro[2,3-b]benzofurans (5), which have been separated and identified by proton and13C nmr spectroscopy. Based on the isolation of two chromene intermediates and their conversion to3and4, as well as the isomerization of3to4and4to5, a "double Claisen" mechanism is proposed. The reaction is not regiospecific but the two [3,3] sigmatropic shifts occur preferentially to theparapositions of the methoxy substituents.

ISSN:0008-4042    

DOI:10.1139/v86-329

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The1Hmr spectra of 20 catechin derivatives substituted at C-6/C-8 by bromine and/or hydrogen and at oxygen by methyl, acetyl, and/or hydrogen have been analyzed in deuterated acetone, acetonitrile, and chloroform. Because of its dependence on the nature of the solvent and of the oxygen substituent, the difference between H-6 and H-8 chemical shifts has been found to be an unreliable criterion for the distinction between 8-bromo and 6-bromo isomers. In methylated catechins, double irradiation of H-8 and H-6 enhances one (MeO-7) and two (MeO-5 and MeO-7) methoxy signals, respectively, via the nuclear Overhauser effect. This permits unambiguous assignment of chemical shifts to all ring A protons. The H-6 and H-8 resonance frequencies of catechin have been determined by decoupling of the OH-5 and OH-7 protons.

ISSN:0008-4042    

DOI:10.1139/v86-330

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

In argon atn = (2–6) × 1024 molecules/m3, the density-normalized mobilitynμ of argon cations at low electric field strengthsE/nis constant from 150 to 300 K; at > 300 Knμ increases. The increase was smaller when the "effective" temperatureTeffof the ions was increased by applying higherE/nat 300 K. At 630 K,whereas in xenon it was 2.7, and in helium 1.0. The difference in behavior is attributed to the main ions being dimersin argon and xenon collision-induced dissociation can occur:where * indicates excess kinetic energy acquired by acceleration in the electric field. The dissociation energies ofandare 2.3, 1.3, and 0.7 eV, respectively. Dissociation ofis negligible because of its large dissociation energy. Dissociation ofand reformation ofis equivalent to the inelastic de-excitation of

ISSN:0008-4042    

DOI:10.1139/v86-331

出版商:NRC Research Press    

年代:1986

数据来源: NRC