摘要:

The mechanism of the hydrogen evolution reaction on niobium is evaluated in alkaline media at 24 °C. The reaction order of zero, along with the observed Tafel slopes of 120 mV/decade (standard deviation 8 mV/dec.), indicate the Heyrovsky reaction mechanism to be applicable for the hydrogen evolution reaction. The presence of anions such as sulfate and chloride does not influence the mechanism.

ISSN:0008-4042    

DOI:10.1139/v77-057

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Dissociation of Br2in Ar was studied at 3500 K using classical 3-D trajectory technique, and compared with earlier trajectory calculations. Some of the assumptions used previously were eliminated, while others were studied in some detail. The one-way flux, equilibrium rate coefficient, obtained from over 8400 trajectories, was found to be over an order of magnitude larger than the experimental rate constant. This was taken as an indication that at high temperatures the nonequilibrium effects are important in dissociation reactions. In order to understand these effects better, additional calculations using an improved set of assumptions were performed. The calculated dissociation rate constant for Br2 + Ar → 2Br + Ar reaction, which accounted for nonequilibrium effects, agrees reasonably well with experimental results.

ISSN:0008-4042    

DOI:10.1139/v77-058

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Photolysis of aromatic azoxy compounds in non-basic solvents in the presence of 2-naphthol leads quite generally to azonaphthols in addition to the normal photorearrangement product. Free diazonium ions are implicated as the precursors of the azonaphthols, both the latter and the usual photorearrangement product being derived from the same excited state of the azoxy compound. Variation of the solvent, light intensity, substrate concentration, and percent reaction all cause changes in the product distribution. Such changes can be accommodated by postulating an intermediate which can either afford the normal rearrangement product by loss of a proton to a weak base, or expel a diazonium ion when no base is present.

ISSN:0008-4042    

DOI:10.1139/v77-059

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Direct irradiation of the charge-transfer complex between the cyclopropenes 3,3-dimethyl-1,2-diphenylcyclopropene (3) and 1,2,3-triphenylcyclopropene (7), and the electron deficient olefins dimethyl fumarate (5) and maleic anhydride (11) resulted in formation of the cycloadducts6,12–15which are the bicyclo[2.1.0]pentane derivatives. These products were also formed when the reaction was photosensitized by triplet–triplet transfer. The structure of the adducts rests largely upon the interpretation of13C and1H nmr spectra. Nuclear Overhauser effect studies were used to assign stereochemistry. The thermal stability of these new bicyclo[2.1.0]-pentane derivatives has been examined, particularly with regard to the ring-flipping process and the rearrangement to the corresponding cyclopentene derivatives.

ISSN:0008-4042    

DOI:10.1139/v77-060

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A thorough examination of the aqueous oxidative chlorination of 1,3,5-trithiane is described. The results are utilized to explore and delineate the scope of a general, stepwise, oxidative cleavage reaction of dialkyl sulfides in which they are successively halogenated and oxidized to α-polychlorosulfoxides; subsequently, these cleave to form sulfinyl chlorides, which hydrolyze and become further oxidized to yield alkanesulfonyl chlorides. The overall stepwise process is named the 'Sulfohaloform reaction' and the structural requirements of the substrates at each step are explored in detail. A practical, general synthesis of sulfonyl chlorides is presented.

ISSN:0008-4042    

DOI:10.1139/v77-061

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Details are provided of synthetic routes from dialkyl sulfides to both α-halosulfoxides and sulfinyl chlorides. In the case of the former, oxidation of α-halosulfides to the sulfoxide stage is achieved by chlorine in acetic acid containing controlled amounts of water. Sulfinyl chlorides are prepared by chlorination of α-polyhalosulfoxides in methylene chloride. During investigations into the details of the sulfohaloform reaction, a number of novel redox reactions involving oxygen transfer between sulfur species have been observed and these are presented. They include a reduction of a sulfoxide with thionyl chloride.

ISSN:0008-4042    

DOI:10.1139/v77-062

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The preparation of the title compounds is described. The cyclization of thesyn- andanti-isomers of semicarbazones, thiosemicarbazones, and carbomethoxymethyl hydrazones to azauracils, thioazauracils, and pyrazoles is described. The photochemical isomerization of the hydrazones has been carried out. Whereas bothsyn- andanti-isomers of the thiosemicarbazones and carbomethoxymethyl hydrazones cyclize, only thesyn-isomer of the semicarbazones can be converted to the corresponding azauracil.

ISSN:0008-4042    

DOI:10.1139/v77-063

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Syntheses of 1-o- and 1-m-chlorobenzoylisoquinolines are described, (a) from 2-benzoyl-1,2-dihydroisoquinoline-1-carbonitrile and the appropriate chlorobenzaldehyde, and (b) from 2-o- and 2-m-chlorobenzoyl-2-dihydroisoquinoline-1-carbonitrile. Treatment of either ketone with potassamide - potassiumtert-butoxide in ammonia givesN-(1-isoquinolinyObenzamide. The mechanism of this reaction is discussed.

ISSN:0008-4042    

DOI:10.1139/v77-064

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The crystal structure and absolute configuration of an optically active dioxygen complex of cobalt(III) have been determined from three dimensional X-ray diffraction data collected by counter techniques. (+)546-Δ-cis-β-[Co{R,R-(CH3)2As(CH2)3As(C6H5)(CH2)2As(C6H5)(CH2)3As(CH3)2}O2]ClO4crystallizes in the orthorhombic space groupP212121, in a unit cell of dimensionsa = 12.595(7),b = 20.937(10), andc = 11.509(6) Å. There are four formula units per cell. The structure was refined onFby full matrix least-squares techniques, and converged with an agreement factorR = 0.0474 based on 2988 independent observations collected from two crystals. The absolute configuration of the cation was determined by the Bijvoet absorption edge technique to be Δ. The tetradentate ligand adopts thecis-β configuration around the cobalt atom. One six-membered ring has a chair conformation; the other is disordered, and occurs with equal probability in a chair and a distorted boat conformation. The five-membered chelate ring has agaucheconformation, of absolute configuration λ. The absolute configurations at the asymmetric arsenic atoms are bothR. The O—O bond length is 1.424(10) Å. The assignment of formal oxidation states to the cobalt atom and the dioxygen ligand is discussed in light of the molecular geometry and the optical properties of the cation.

ISSN:0008-4042    

DOI:10.1139/v77-065

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The bicyclo[2.2.2]octan-2-one and -[3.2.1]octan-6-one skeletons are interconvertible under strongly basic conditions. Their α,α-dimethyl derivatives intert-Buo−/tert-BuOH at 185 °C undergo very slow interconversion by β-proton abstraction. Using2H nmr the stereoselectivity of deuterium incorporation at the β-methylene sites was established. The relative reactivities of β-methyl exchange in the [3.2.1] system were also determined. As models for this process, exchange in the α,α,α′,α′-tetramethyl derivatives of the monocyclic ketones, C5–C8, was also studied.

ISSN:0008-4042    

DOI:10.1139/v77-066

出版商:NRC Research Press    

年代:1977

数据来源: NRC