摘要:

A compound prepared by refluxing methyl benzoate with boron sulfide (B2S3) and previously identified as tetraphenyl-p-dioxin has been identified in this investigation as tetraphenylthiophene.

ISSN:0008-4042    

DOI:10.1139/v78-176

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Experiments are described whose results indicate that semiquinones produced by intramolecular photoreduction of FMN in basic solution are responsible for specific line broadening observed in the13C nmr spectrum. Tests with oxidizing agents as well as singlet and triplet quenchers are shown to support this theory rather than the proposition that the paramagnetic species effective in relaxation enhancement is a flavin triplet state. A mechanism for the production of semiquinones and their interaction with the FMN population is discussed.

ISSN:0008-4042    

DOI:10.1139/v78-177

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Oxidation of haplophytine (1) with alkaline potassium permanganate has been shown to give the seco product16. This assignment is based on spectroscopic data and comparison of these with spectroscopic data for the analogous seco product8formed on similar oxidation of aspidophytine (3), an acid cleavage product of haplophytine. The course of these oxidations contrasts with that of the oxidation of haplophytine and aspidophytine with alkaline hydrogen peroxide, which gives4and6, respectively, without carbon–carbon bond cleavage.

ISSN:0008-4042    

DOI:10.1139/v78-178

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The properties of the 1,3-cyclohexanedione system in 2-deacetylchelocardin (2) andN-carbobenzoxy-2-deacetylchelocardin (3) are found to be significantly different from those of ordinary 1,3-cyclohexanediones. Acylation and alkylation of (2) or (3) generally givesO-acylation orO-alkylation products. However, reaction ofN-carbobenzoxy-2-deacetylchelocardin (3) with methyl orthoformate orN,N-dimethylformamide dimethyl acetal leads exclusively toC-acylation products.

ISSN:0008-4042    

DOI:10.1139/v78-179

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Nitration of l-chloro-2,3-dimethylbenzene in acetic anhydride gives thecisandtransisomers of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl acetate (29%) and l-chloro-2,3-dimethyl-4-nitro- (46%), -5-nitro- (5%), and -6-nitrobenzene (20%). In formic acid and acidified methanol, exchange of acetate for formate and methoxyl, respectively, occurs and the diastereoisomers of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl formate and methyl ether, respectively, are formed. Rearomatization of each isomer of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl acetate in acetic acid results in initial isomerization to form the pair of diastereoisomers and subsequent elimination of nitrous acid to form 3-chloro-4,5-dimethylphenyl acetate. In 25% trifluoroacetic acid in deuteriochloroform elimination of acetic acid and migration of the nitro group to form 1-chloro-2,3-dimethyl-4-nitro-benzene and a lesser amount of its 6-nitro isomer is the dominant reaction. In the presence of mesitylene the formation of the nitro derivatives is suppressed and 3′-chloro-2,4,4′,5′,6-pentamethylbiphenyl is obtained. It is proposed that cyclohexadienyl cations are significant intermediates in ail of the reactions. Pyrolysis of the adducts gives 1-chloro-2,3-dimethylbenzene as the major product.

ISSN:0008-4042    

DOI:10.1139/v78-180

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The gas phase ion molecule reactions of a number of potential fluoride donors with carbon dioxide and carbonyl fluoride have been studied. By determination of preferential directions of fluoride transfer the fluoride affinities of carbon dioxide and carbonyl fluoride have been bracketed and found to be 33 ± 3 kcal/mol and 35 + 3 kcal/mol respectively. In addition, from gas phase acidity studies of acetyl fluoride and 2-fluoropropene the fluoride affinities of ketene and allene have been calculated to be 38 ± 2 kcal/mol and 15 ± 2 kcal/mol respectively. The order of fluoride affinities (Lewis acidities) of carbon dioxide, ketene, and allene have been examined and explained in terms of the electron affinities of the F—C(A)(B) species (A,B=O,CH2) and the C—F bond dissociation energies. These quantities have been estimated and the latter interpreted on the basis of the π bond energies of the three compounds.

ISSN:0008-4042    

DOI:10.1139/v78-181

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The yield of nitrogen from the radiolysis of nitric oxide is G(N2) = 4.5 ± 0.3 at doses from 0.1 to 1.0 × 1020 eV g−1and at dose rates of 2.5 × 1016and2 × 1027 eV g−1.s−1. The addition of SF6to NO does not change this yield but in mixtures of NO with 90% Xe the addition of SF6reducesG(N2) by an amount close toG(Xe+). These results are consistent with suppression of dissociative neutralisation in NO by clustering of the positive ion. Good agreement is obtained between the total energy absorbed and the amounts required for ionization, neutral dissociative excitation, and formation of subexcitation electrons. The neutral dissociative excitation yield is estimated to beG(NO → N + O) = 3.6 ± 0.3.

ISSN:0008-4042    

DOI:10.1139/v78-182

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Flash photolysis of bis[piperidyl-1] disulfide gave a clear transient band at 340 nm and a weak band around 525 nm, which were assigned to the piperidyl-1-thiyl radical. In a similar manner, bis[diphenylimino] disulfide gave a transient band at 420 nm, which could be assigned to the diphenyliminothiyl radical. These radicals disappeared in various solvents according to second-order kinetics with rate constant 0.8–7.2 × 109 M−1s−1showing that the radicals decay predominantly by recombination with diffusion controlled rates. These radicals were not reactive toward oxygen, olefins, organophosphorous compounds, and hydrogen donors in agreement with the results given by the kinetic epr study reported by Maillard and Ingold.

ISSN:0008-4042    

DOI:10.1139/v78-183

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Metal complexes of water-soluble and other porphyrins have been prepared by a heterogeneous reaction with the metal reactant present in an insoluble form. The oxidation state of the metal is important in the reactions. Metal reactants in the lower oxidation states (0, I, II) react with porphyrins but those in the higher oxidation states (III, IV) do not. Metalloporphyrins of high purity may be conveniently prepared by this method.

ISSN:0008-4042    

DOI:10.1139/v78-184

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Species formed on evaporated copper surfaces, both clean and oxide-covered, were examined using ir ellipsometric spectroscopy (IRES). Spectra were obtained for CO adsorbed on both bare and oxide-covered copper, the spectra being in accord with published data. No spectra were observed for formic acid adsorption unless free oxygen was present, in which case a spectrum characteristic of a carbonate species was found. Supporting data were obtained to show that the carbonate species was formed by reaction of formic acid and oxygen on the oxide-covered surface. These data illustrate some of the unique advantages of IRES for studying molecular processes on surfaces.

ISSN:0008-4042    

DOI:10.1139/v78-185

出版商:NRC Research Press    

年代:1978

数据来源: NRC