摘要:

Spin–lattice relaxation times for the13C nuclei of adamantane and the2H nuclei of adamantane-d16are reported for most of the temperature range of the solid I (plastic) phase, and for the solid II phase just below the transition point. Angular correlation times are shown to be in good agreement with those previously obtained from proton nmr data by Resing.

ISSN:0008-4042    

DOI:10.1139/v80-099

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The structure of (4′-carbomethoxy-2′-nitrophenoxy)benzene, C14H11NO5, has been determined by X-ray diffraction. The crystals are monoclinic,a = 8.880(7),b = 9.792(4),c = 14.820(5), β = 90.07(5),P21/cwithZ = 4. The integrated intensities of 2966 independent reflections were measured on a four-circle diffractometer, 2072 of which were used in the refinement to give a final least-squares weighted residual of 0.062 and a conventionalRfactor of 0.086. The absence oforthosubstituents on one ring of the molecule allows it to adopt the twist-nitro-distalconformation. The lengths of the bonds from the unsubstituted ring and the substituted ring to the bridging oxygen atom are 1.409(3) and 1.353(3) Å respectively. The torsional angles about those bonds are 54.6° and 16.5°. The angle subtended at the bridging oxygen atom is 120.0(3)°.The unusual thermal ellipsoids associated with one of the nitro oxygen atoms of this structure and with a nitro oxygen atom of three related structures occur when the nitro substituent is nearly coplanar with the phenyl ring on which it is substituted and also has a neighbouring substituent or bridging group. The unusual thermal ellipsoids then result from repulsive exchange forces.

ISSN:0008-4042    

DOI:10.1139/v80-100

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Crystals of [Pt(Et4dien)I]I, where Et4dien = (C2H5)2NC2H4NHC2H4N(C2H5)2, have been prepared. A three dimensional crystal structure analysis has been carried out in a monoclinic unit cell havinga = 12.565(8),b = 7.576(6),c = 21.040(15) Å, β = 91.12(2)° and space groupP21/c,Z = 4. Full-matrix least-squares using 1982 independent, observed reflections converged atR = 0.067. The platinum atom has square-planar co-ordination. The orientation of the four ethyl groups with respect to the plane of the ligand is similar to that observed in related molecules, in spite of a lack of similarity of the molecular packing. The iodide ion appears to be hydrogen bonded to the ligand.

ISSN:0008-4042    

DOI:10.1139/v80-101

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

In order to obtain further understanding of the nature of lignin reactions during autocatalysed hydrolysis (autohydrolysis) of wood, milled wood lignin (MWL) was isolated from aspen (Populus tremuloides) and treated under autohydrolysis conditions. By this means reactions of the lignin itself could be distinguished from those taking place between lignin and the carbohydrate or other components of the wood. The material after the reaction was separated into a dioxane insoluble fraction (DI), a dioxane soluble but ether insoluble fraction (DSEI), and an ether soluble fraction (ES). Studies were carried out on the DI and DSEI fractions; no direct study was made of the small ES fraction.The formation of DI material increased linearly during the first 7.5 min at 170 °C and then levelled off. At the same time DSEI decreased and then levelled off. Gel permeation chromatography of the DSEI fraction suggested that during autohydrolysis there is an initial generation of low molecular weight fragments which recombine to form first a high molecular weight soluble fraction and from this the insoluble product. The DSEI fraction contained increased conjugated and unconjugated keto groups. Carboxylic acids were also detected; they have been attributed to the reincorporation of low molecular weight aromatic acids generated by the hydrolysis of the corresponding esters. The dioxane insoluble (DI) fraction had fewer unconjugated keto groups than the DSEI fraction, indicating that these groups participated in the condensation reactions leading to the formation of insoluble material. These probably involve position 6 of the aromatic ring.

ISSN:0008-4042    

DOI:10.1139/v80-102

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Isopropylperoxy radicals at low temperatures exist in equilibrium with di-isopropyl tetroxide. The thermodynamic parameters for this equilibrium are very similar to the values of ΔH0and ΔS0for thetert-butylperoxy radical – di-tert-butyl tetroxide equilibrium. Differences in second-order rate constants for mutual destruction of secondary and tertiary alkylperoxy radical appear to result from differences in rate constants for unimolecular decomposition of secondary and tertiary alkyl tetroxides.Isopropylperoxy radicals have the same termination rate constant in the gas phase and in solution.

ISSN:0008-4042    

DOI:10.1139/v80-103

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Field desorption mass spectra have been recorded for most of the 45 cryptates which may be formed from complexation of [2.2.2]-, [2.2.1]-, and [2.1.1]-cryptand with Li+, Na+, an d K+ions in combination with the anions Cl−, Br−, I−, OTs−, and BPh4−. The cryptate cation predominated in almost all of the spectra. The stability of the complexes was found not to be simply related to goodness of fit of the cation in the cryptand cavity, but a significant trend in stability in the order BPh4 > 1 > Br > Cl was found. This order of complex stability was shown to be consistent with known thermodynamic parameters. These results are discussed briefly in terms of applications to analysis of alkali metal cations.

ISSN:0008-4042    

DOI:10.1139/v80-104

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The oxidation of 2,4,6-tritertbutylphenol and several other alkyl and halophenols by CrO2Cl2and VOCl3was studied. The products of CrO2Cl2oxidation are mostly quinones and diphenoquinones, whilst those of VOCL3oxidation also include major amounts of dealkylated phenols and C—C coupled dimers. The product distributions are interpreted in terms of a mechanism involving phenoxyl radicals, ligand transfer from metal to radical, and either phenoxonium ions or metallate esters where there is sufficient electron withdrawal from the organic group for it to exhibit carbenium ion properties. The differences in behaviour between CrO2Cl2, VOCl3, and CuCl2are attributed to different balances between the oxidation potential and Lewis acidity of the metal complexes. It is concluded that CrO2Cl2is not a good model for proposed ferryl intermediate in heme oxidase systems since it induces 1 → 3 rather than 1 → 2 halogen shifts and an NIH shift that is best explained by carbenium ion-like intermediates.

ISSN:0008-4042    

DOI:10.1139/v80-105

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

N1sbinding energies for 36 pyridines substituted at the 2-, 3-, and 4-positions have been determined by X-ray photoelectron spectroscopy. The differences in BE relative to pyridine are analysed in terms of existing theoretical approaches (electrostatic, ground potential, and relaxation potential models) and compared withvalues calculated for analogous monosubstituted benzenes. One finds good correlations ofwith solution determined σ-substituent values although some substituent values deviate from the correlation probably due to solution effects which are not present in the gas phase. Correlations betweenand14N nmr chemical shifts are poor, particularly for electron withdrawing substituents. The relationship betweenand gas phase basicity values (ΔG0) is good, and it appears as if theis more sensitive to the substituent than ΔG0. MINDO/3 calculations on the methoxypyridines and their conjugate acids employing full geometry optimizations are presented and analysed in order to determine the effect of geometric relaxation on the gas phase basicity.

ISSN:0008-4042    

DOI:10.1139/v80-106

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Measurements at 25 °C with flow calorimeters and densimeters have led to heat capacities and densities of aqueous solutions of 15 unsaturated heterocyclic compounds containing nitrogen. From the results of these measurements we have obtained apparent molar heat capacities and volumes of the solutes. Extrapolations to infinite dilution have led to corresponding standard state apparent and partial molar heat capacities and volumes, which have been analyzed in terms of atomic and group additivity relationships.

ISSN:0008-4042    

DOI:10.1139/v80-107

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The crystal structures of Sb2Tl7, Cu5Zn8, and Ir3Ge7are discussed with the aid of shortest distances of Dirichlet domains and of voids in their frameworks. It will be pointed out that all three frameworks must be regarded as different though relations between the atomic parameters are obvious. The Sb2Tl7structure represents a superstructure of anIlattice. The frameworks of Sb2Tl7and of Cu5Zn8contain tetrahedral voids only, while in Ir3Ge7voids with a larger coordination number also exist.

ISSN:0008-4042    

DOI:10.1139/v80-108

出版商:NRC Research Press    

年代:1980

数据来源: NRC