摘要:

Carbeneiron porphyrins, (N,Fe)-bridged methyleneiron porphyrins,N-alkyliron porphyrins and σ-alkyliron porphyrins have all been shown to occur in nature and to be interconvertible via redox reactions. The chemistry of the naturally occurring iron porphyrins and model iron, cobalt, and ruthenium porphyrins is reviewed emphasizing their organometallic chemistry.

ISSN:0008-4042    

DOI:10.1139/v87-080

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The electron donor–acceptor molecular complexes between thiazole and some of its derivatives and iodine in several solvents have been investigated spectrophotometrically at different temperatures. Spectral characteristics, equilibrium constants,K, extinction coefficients, ϵ, and thermodynamic functions of formation, ΔH0, ΔG0, and ΔS0have been determined. It was found that the data fit satisfactorily the 1:1 stoichiometric equilibrium: D + I2 = DI2"outer complex". The EDA complexes obtained are of "n–σ*" type in which the nitrogen atom of thiazole is the donor center. Moreover, the effect of solvents on theKvalues is discussed in terms of the solute–solute and solute–solvent competing equilibria.

ISSN:0008-4042    

DOI:10.1139/v87-081

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Eleven stationary points on the singlet C2H2F3+potential energy surface have been calculated using the 3-21G basis set, and characterized as minima (four structures) or first-order saddle points (seven structures) by vibrational analysis. To check the reliability of this basis set, three of the structures have also been optimized at the 6-31G* level; although the geometries change somewhat, the relative energies and nature (maxima, minima) of the structures remain the same. For CF3CH2+the minimum energy structure has one C—F bond coplanar with the vacantp-atomic orbital at the cationic centre. The structure is 16.4 kcal/mol less stable than the lowest energy conformation of FCH2CF2+, and the barrier for the 1,2 fluorine migration which connects the two structures is low. The cation F2CHCHF+has a conformation that is a minimum on the potential energy surface that is 16.9 kcal/mol higher in energy than FCH2CF2+; the two structures are separated by a barrier for 1,2 hydrogen migration of 23.5 kcal/mol. The electronic effects in the various structures have been studied using a quantitative PMO analysis of the interactions between the two carbon fragments of the ions. For CF3CH2+the net effect of the fluorine is highly destabilizing; the principal stabilizing interactions between CF3+and CH2consist of π donation from CF3+to CH2and homoconjugation of a fluorine lone pair with the cationic centre. No net stabilization attributable to fluorine bridging could be found.

ISSN:0008-4042    

DOI:10.1139/v87-082

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The 1-hydroxy substituent in 1-hydroxy-1,3-dihydrobenzo[c]thiophene 2,2-dioxides is readily replaced by alkoxy, alkylthio, and amino groups. These compounds serve as precursors of alkoxy, alkylthio, and amino substitutedo-quinodimethanes. Cycloaddition reactions between a series of 1,4-disubstitutedo-quinodimethanes bearing a phenyl group and one of the above heteroatoms, and typical dienophiles such as dimethyl fumarate and methyl crotonate were carried out. The phenyl group controlled both the regiochemistry and stereochemistry of these cycloaddition reactions, with the major products beingtrans-1-phenyl-2-carbomethoxytetrahydronaphthalenes. The amino substitutedo-quinodimethanes were trapped only by dimethyl fumarate.

ISSN:0008-4042    

DOI:10.1139/v87-083

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Diozonolyses in methanol of (E)-4-chloro-2,3-dimethyl-1,3-hexadiene (4a) and of (4E)-5-chloro-3,4-dimethyl-2,4-heptadiene (4b) resulted in complete cleavage of the double bonds and of the single bonds of the respective diene systems. The course of these anomalous cleavage reactions has been established by step-wise ozonolyses of these dienes, and by the identification of labile methoxy hydroperoxides as intermediates.

ISSN:0008-4042    

DOI:10.1139/v87-084

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A systematic Raman spectroscopic investigation of the complexation of CH3Hg+by the standard amino acids is reported. It is shown that the vibrational bands due to the ligand—Hg and Hg—CH3stretching modes and to the symmetric —CH3bending mode of the —HgCH3unit are well suited to characterize the extent of complexation and the sites of attachment of the cation. Coordination, which occurs mostly on sulfur and nitrogen atoms by substitution of a proton on the thiol group of cysteine or on amino groups in general, is best identified by the frequency of the ligand—Hg stretching vibration in the 250–550 cm−1region of the spectrum.

ISSN:0008-4042    

DOI:10.1139/v87-085

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

In acidic solutions of chlorite and bromide two processes occur simultaneously, the disproportionation of chlorite and an autocatalytic reaction leading to a rapid production of ClO2. The unusual features of this reaction are described. In this complex system the rate of HClO2 + Br− + H+ → HClO + HBrO cannot be measured. It can be, however, with addedortho-tolidine to remove the HBrO and HClO. We obtainedr = k[HClO2][Br−][H+] withk = 1.48 × 10−2 M−2s−1at 25 °C. Without addedortho-tolidine this reaction initiates the autocatalytic reaction for which we suggest a kinetic scheme.

ISSN:0008-4042    

DOI:10.1139/v87-086

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The fungusMortierellaisabellinacan convert ethylbenzene and a number ofpara-substituted derivatives to the corresponding optically active 1-phenylethanols with enantiomeric excesses between 5 and 40% and chemical yields up to 45%. 2-Ethylnaphthalene, 2-ethylthiophene, andn-propylbenzene were similarly converted, as were the bicyclic compounds indane and tetralin. In most cases, theRabsolute configuration of product predominated. The fungiCunninghamellaechinulatavar.elegansandHelminthosporiumspecies are also capable of performing some of these transformations.M.isabellinaandC.elegansalso produce 2-phenylethanols as products in some cases. The highest enantiomeric excesses during benzylic hydroxylation were obtained withHelminthosporiumand are attributable, at least in part, to further stereoselective oxidation of the alcohol. Cross induction experiments withM.isabellinaindicate that the same enzyme may be responsible for the benzylic hydroxylation of ethylbenzene, 2-ethylthiophene, and 2-ethylnaphthalene.

ISSN:0008-4042    

DOI:10.1139/v87-087

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Deoxyribonucleic acid (DNA) adsorption on one sample of Canadian chrysotile and two samples of chrysophosphate has been studied using chemical analysis and a surface method of analysis (photoelectron spectroscopy, XPS). Chrysophosphate was obtained using a phosphorylation process applied to chrysotile fibres; one chrysophosphate sample was opened in a Pallmann device. XPS analysis of the samples before DNA adsorption has shown that some surface phosphorus was dissolved following suspension of the fibres in distilled water. After DNA treatment, the amount of DNA adsorbed at the surface of the chrysophosphate sample was lower than that adsorbed at the chrysotile surface (12.6 ± 1.7 μg/mg and 74.0 ± 4.0 μg/mg respectively). In addition, the opened sample adsorbed an intermediary DNA amount (28.3 ± 5.6 μg/mg), suggesting that the phosphorylation process has not reached all the bulk fibres. The results indicate that DNA adsorption is a sensitive method for investigation of the surface state of the fibre. Moreover, it seems that the phosphorylation process masks or blocks the reactive surface sites for DNA adsorption.

ISSN:0008-4042    

DOI:10.1139/v87-088

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Electrical breakdown voltage studies on Nb2O5films in aqueous solutions of weak organic acid as a function of concentration, temperature, and applied field are carried out under galvanostatic conditions. Electronic conduction measurement through the Nb2O5film as a function of temperature and applied field are also determined so as to examine the validity of Ikonopisov theory of electrical breakdown quantitatively.

ISSN:0008-4042    

DOI:10.1139/v87-089

出版商:NRC Research Press    

年代:1987

数据来源: NRC