摘要:

A convenient and general method for the synthesis of cyclic and acyclic imides, sulfonimides, andN-benzyloxycarbonyl amides via the inter-and intramolecular trapping of ketenes has been developed. Heating the corresponding amido, sulfonamido, and carbamamido ethyl ethynyl ethers at 150 °C for 3 h produced the desired compounds in good to excellent yields.Keywords: ketenes, imides, sulfonimides,N-benzyloxycarbonyl amides.

ISSN:0008-4042    

DOI:10.1139/v95-260

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The metabolites of the wood rot decay fungusSistotremaraduloides(P. Karst) Donk have been investigated and a new type of norpentaketide has been discovered. The compounds sistodiolynne (1), sistolynone (5), and sistopyrone (6) represent new carbon skeletons among natural products. The compounds are very unstable and readily polymerize in the presence of air to give black insoluble material. It has been shown by13C NMR labelling experiments that they arise from five acetate units, and that a methyl carbon of one of the acetate units is lost during the biosynthesis. The structures were determined by spectroscopy methods, mainly NMR, and the absolute configuration of sistodiolynne was established by circular dichroism methods.Keywords: fungal metabolites,Sistotremaraduloides, norpentaketides, biosynthetic studies, polyacetylenes.

ISSN:0008-4042    

DOI:10.1139/v95-261

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The optical absorption spectra of es−in 1-butylamine–water mixed solvents increase smoothly in energy and intensity as the water content is increased, with the exception of a small decrease in intensity on going from 95 to 100 mol% water. At 298 K the value ofGϵmaxincreases from 1.42 × 10−21 m2/16 aJ (8.6 × 103es−L/100 eV mol cm) in pure 1-butylamine to 8.3 × 10−21 m2/16 aJ (50 × 103es−L/100 eV mol cm) in pure water, and the value ofEAmaxincreases from 115 zJ (0.72 eV) to 278 zJ (1.74 eV). In the pure amine, ifG(es−) = 0.27, then ϵmax = 5.3 × 10−21 m2/es−(3200 m2/mol). The solvent composition dependences ofGϵmaxandEAmaxindicate little selective solvation of es−by water; this might be due to relatively "ideal" mixing of water and amine in the binary solvents. The temperature coefficient −dEAmax/dT = 0.43 zJ/K in pure 1-butylamine, 0.47 in pure water, and has a minimum of 0.27 in the 50:50 mixture.Keywords: 1-butylamine–water mixed solvents, optical absorption spectra, solvated electron, temperature dependence.

ISSN:0008-4042    

DOI:10.1139/v95-262

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The electrical conductance of LiNO3intert-butanol–water mixed solvents changes gradually from "normal" in pure water to "abnormal" in puretert-butanol. In water the measured specific conductance increases with increase of temperature, and intert-butanol the conductancedecreaseswith increase of temperature. In puretert-butanol, the electrical conductances of NH4ClO4and LiClO4increase with the salt concentration and temperature at lower temperatures, but decrease at higher temperatures. The molar conductivity Λ0(10−4 S m2mol−1) intert-butanol at 300 K is 5.0 for NH4ClO4and 4.0 for LiClO4. Both activation energiesEΛ0are 17 kJ mol−1, which gives an unusual correlation between Λ0and viscosity η(mPa s):The values of Λ0for NH4NO3and LiNO3intert-butanol could not be measured, because ion aggregation is significant even at the lowest concentrations required to obtain conductances sufficiently above that of the solvent. The measured temperature coefficient of LiNO3conductance intert-butanol is negative. Ion clustering of nitrate salts is attributed to poor solvation of the planar NO3−ions by the globulartert-butanol molecules. Ion aggregation intert-butanol increases with increasingT, due to the relatively rapid decrease of the value of ϵT. Corrections are listed for reaction kinetics parameters for nitrate salts in puretert-butanol solvent reported in Can. J. Chem.73, 392 (1995).Keywords:tert-butanol, ion-pair aggregation, lithium nitrate, electrical conductance, solvent effects.

ISSN:0008-4042    

DOI:10.1139/v95-263

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

In this publication we report: (i) the rate constants for reaction of the hydrated electron with 1-hexyn-3-ol ((8.6 ± 0.3) × 108 dm3mol−1s−1at 18 °C), cinnamonitrile ((2.3 ± 0.2) × 1010 dm3 mol−1s−1at 20 °C), and 1,3-diethyl-2-thiourea ((3.5 ± 0.3) × 108 dm3 mol−1s−1at 22 °C). For cinnamonitrile and diethylthiourea, the temperature dependence up to 200 °C and 150 °C, respectively, is also reported; (ii) the rate constants for the reaction of the hydroxyl radical with 1-hexyn-3-ol ((5.5 ± 0.5) × 109 dm3 mol−1s−1at 20 °C), cinnamonitrile ((9.2 ± 0.3) × 109 dm3 mol−1s−1at 21 °C), and diethylthiourea ((8.0 ± 0.8) × 108dm3 mol−1s−1at 22 °C). For cinnamonitrile, the temperature dependence up to 200 °C is also reported; (iii) the rate constant for the hydrogen atom reacting with 1-hexyn-3-ol ((4.3 ± 0.4) × 109 dm3 mol−1s−1at 20 °C).Keywords: radiolysis, corrosion inhibitors, rate constants.

ISSN:0008-4042    

DOI:10.1139/v95-264

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

In acidic medium (pH ≈ 1)4-nitrosophenol irradiated in the range 296–366 nm is mainly transformed into benzoquinone (75–80%). The quantum yield of this reaction is wavelength dependent: it is about 6 times higher at 365 nm than at λ ≤ 313 nm. This phenomenon is attributed to an equilibrium between two tautomeric forms, nitroso and quinone monooxime, the former being much more photoreactive than the latter. In unbuffered aqueous solution (pH = 5–6) the formation of an intermediate is observed. Its HPLC retention time is just a little shorter than that of benzoquinone and the maximum of its absorption band is located at 235 nm. The rate of transformation of this intermediate increases with decreasing pH.Keywords: photochemistry, 4-nitrosophenol, wavelength effec

ISSN:0008-4042    

DOI:10.1139/v95-265

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The porphocyanine nucleus contains six nitrogen atoms, four of which are theoretically capable of accepting a proton in acidic solution. However, only the monoprotonated and diprotonated forms have been observed. These two forms were characterized by their visible and fluorescence spectra. pKavalues of 6.0 ± 0.1 and 4.4 ± 0.1 were determined by spectrophotometric titration. The monoprotonated monocationic form can be observed in methanol.Keywords: porphocyanine, protonation, octaethylporphocyanine, octaethylporphyrin.

ISSN:0008-4042    

DOI:10.1139/v95-266

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The oxidation of 1-(4-ethoxy-3-methoxyphenyl)propane (2) and 1-(4-ethoxy-3-methoxyphenyl)propene (3) bymeso-tetra(2,6-dichloro-3-sulphonatophenyl)porphyrin iron chloride (TDCSPPFeCl,1) andtert-butylhydroperoxide (t-BuOOH) are discussed. In addition to a Cα-hydroxylation product, demethoxylation and direct aromatic ring cleavage products were found in the oxidation of2. When3was oxidized by1andt-BuOOH in aqueous acetonitrile, an acetonitrile-incorporated product was found. A mechanism for the oxidation of3is proposed.Keywords: lignin, ligninase, iron porphyrin, model, degradation.

ISSN:0008-4042    

DOI:10.1139/v95-267

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Our study of the photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction has been extended to include alk-4-enols. Irradiation of acetonitrile solutions of the alk-4-enols, 6-methyl-5-hepten-2-ol (16) and 5-methyl-5-hexen-2-ol (17), and the aromatic, 1,4-dicyanobenzene (1), leads to cyclized 1:1 (alk-4-enol:aromatic) adducts. The addition of biphenyl (5) to the irradiation mixture, serving as a codonor, increases the yields and the efficiency of formation of the adducts. The structures assigned to the productstrans-2-(isopropyl 4-cyanophenyl)-5-methyltetrahydrofuran (18, 29%) andcis-2-(isopropyl 4-cyanophenyl)-5-methyltetrahydrofuran (19, 24%) from16(reaction [5]), andr-2-(methyl 4-cyanophenyl)-2,t-5-dimethyltetrahydrofuran (20, 13%),r-2-(methyl 4-cyanophenyl)-2,c-5-dimethyltetrahydrofuran (21, 7%),r-3-(4-cyanophenyl)-3,t-6-dimethyltetrahydropyran (22, 11%), andr-3-(4-cyanophenyl)-3,c-6-dimethyltetrahydropyran (23, 2%), from17(reaction [6]), rests mainly upon analysis of the1H and13C nuclear magnetic resonance spectra. The structures of19,22, and23were firmly established by X-ray crystallography. The observed ratio of regioisomers indicates a strong preference for 1,5-exo-trig, relative to 1,6-endo-trig, cyclization of the intermediate alk-4-enol radical cation. The mechanistic implication of these results is discussed.Keywords: photoinduced electron transfer, radical ions, cyclization of radical cations, intramolecular reactions of radical cations.

ISSN:0008-4042    

DOI:10.1139/v95-268

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Thermodynamic data of proton dissociation of 75 organic acids belonging to four classes (protonated amines, aliphatic carboxylic acids, benzoic acids, phenols) have been processed by multivariate chemometric techniques. The variables consist of conventional thermodynamic quantities (Gibbs function, enthalpy, entropy) and of partial components of these quantities (internal and external, electrostatic and nonelectrostatic components). The above data refer to the aqueous medium, at 25 °C andI = 0 mol dm−3. The Gibbs function of deprotonation in the gas phase and the Hammett σ constant have also been considered. Multivariate techniques include Principal Component Analysis, Factor Analysis, and feature selection. Factor Analysis and related concepts have proved to be useful in defining the causes of differences in acid strengths and their respective importance.Keywords: acid dissociation data, chemometrics of; chemometrics of acid dissociation data; factor analysis of acid dissociation data; principal component analysis of acid dissociation data; thermodynamics of acid dissociation.

ISSN:0008-4042    

DOI:10.1139/v95-269

出版商:NRC Research Press    

年代:1995

数据来源: NRC