摘要:

Mixtures ofcis- andtrans-p-menthan-8-ol were prepared by hydrogenation of α-terpineol over platinum or palladium catalysts and the isomer ratios obtained were determined by gas–liquid chromatography. The dehydration of a 1:1 mixture, as well as of the pure stereoisomers, was studied with a number of reagents. Aqueous oxalic and acetic acids, fused potassium hydrogen sulphate, anhydrous oxalic, silicic, and boric acids, and "Florisil" promoted the typical acid-catalyzed dehydration, withp-menth-4(8)-ene and smaller amounts of isomericp-menth-8-enes as the primary products, andp-menth-3-ene the final product owing to isomerization. With anhydrous silicic acid the latter was obtained in better than 80% yield. With non-acidic alumina, or thionyl chloride in excess pyridine, the main product wasp-menth-8-ene (up to 90%); no isomerization top-menth-3-ene was obtained. The possible reaction mechanisms are discussed.

ISSN:0008-4042    

DOI:10.1139/v63-001

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The electron spin resonance of an X-ray irradiated single crystal of diketopiperazine has been measured at 9 Gc/sec for various orientations of the crystal in the static magnetic field. From an analysis of the hyperfine structure observed we have been able to calculate the components of the hyperfine interaction tensor for the radical produced by the irradiation. The principal values for the hyperfine interaction tensor are similar to those found for the radical produced by the X-ray orγ-ray irradiation of glycylglycine and N-acetylglycine and is therefore attributed to a radical with a C—H fragment. The fine details of the spectrum indicate that the radical responsible for the electron resonance observed probably has the structurewhich is formed from diketopiperazine by the loss of a hydrogen atom from one of the CH2groups in that molecule.

ISSN:0008-4042    

DOI:10.1139/v63-002

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Crystals of tri-p-tolylarsine are rhombohedral, with cell dimensions a = 9.84 Å, α = 80° 2′, and space group. There are two molecules in the unit cell, and hence the molecule has symmetry C3. The structure has been determined from a projection along the rhombohedral cell axis, and the bond lengths and valency angles are given. In comparison with an ideal model having maximum interaction between the arsenic lone pair and the aromatic π-electrons, each ring is rotated about its As—C bond by 36°, the three rotations being in the same sense. These displacements increase overcrowded distances in the ideal model to about the normal van der Waals separations, the closest intramolecular contacts between p-tolyl groups beingand. All the intermolecular contacts correspond to van der Waals interactions.

ISSN:0008-4042    

DOI:10.1139/v63-003

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The stability constant of the sodium chelate of EDTA was determined by means of a sodium-sensitive glass electrode. It appears that a hydrogen chelate of the formula NaHY2−is formed in the neutral solution of EDTA, but is very unstable. The stability constants, pKNaY = −2.61 and pKNaHY = 0.03, are comparable to the value obtained by Schwarzenbach and Ackermann under different experimental conditions by a less sensitive method.

ISSN:0008-4042    

DOI:10.1139/v63-004

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The kinetics of electrochemical decarboxylation of formate ions has been studied in detail for the first time as a model reaction for examination of the decarboxylation and radical coupling that occurs with higher aliphatic acids. Current–potential curves have been obtained which show a sharp transition region, not diffusion controlled, which is characteristic of passivation phenomena. The behavior is observed with gold, palladium, platinum, and gold–palladium alloys. Tafel slopes and exchange currents have been evaluated for the reaction and possible reaction mechanisms are examined in relation to the experimental results.Galvanostatic charging, reverse pulse discharging, and open-circuit decay transients have been obtained which indicate formation of films of adsorbed intermediates on the surface. The transition regions in the current–potential curves are associated with formation of this ad-layer. The galvanostatic results enable distinctions to be made between some of the possible reaction mechanisms proposed and estimates to be made of the extent of film formation by adsorbed intermediates formed in the reaction.

ISSN:0008-4042    

DOI:10.1139/v63-005

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Electrochemical kinetic studies on the Kolbe reaction have been carried out in the trifluoroacetate–100% trifluoroacetic acid system, where the reaction can be examined from an electrochemical viewpoint with minimum complication by oxidative side reactions. High yields of the Kolbe products C2F6and CO2are obtained and current–potential curves exhibiting transition behavior and linear Tafel regions are found. Tafel slopes are deduced for "Langmuir" and "Temkin" conditions of surface coverage by intermediates and compared with the experimental observations. Plausible reaction mechanisms are proposed, which are supported by galvanostatic discharge transients; the latter indicate that the coverage by adsorbed intermediates in the trifluoroacetate reaction approaches a monolayer. In the aqueous formate systems, multilayer formation is indicated, including deposition of layers of different species corresponding to different arrest regions in the galvanostatic discharge transients. It is suggested that these layers may consist of oxide and the discharged carboxylate and that the transition behavior and critical potentials in the Kolbe reaction correspond to conditions for passivation of the metal by oxide and carboxylate species.

ISSN:0008-4042    

DOI:10.1139/v63-006

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Galvanostatic cathodic discharge and open-circuit decay transients have been obtained for the decarboxylation of formate in formic acid and interpreted quantitatively in terms of the adsorption of intermediates in the reaction. These intermediates are identified with HCOO•radicals. Extended anodic polarization at platinum and particularly at palladium leads to the formation of films of an anodic product which are considerably thicker than a monolayer. After relatively long times (> 100 seconds) of anodic polarization, the film growth obeys the inverse logarithmic rate law deduced by Mott and Cabrera. The thick films which are formed at palladium are believed to be responsible, upon autocatalytic decomposition, for the delayed gas evolution phenomenon observed at this metal.A new method for deduction of adsorption pseudocapacitance and charge associated with the ad-layer from open-circuit decay curves and Tafel parameters is used to obtain the pseudo-capacitance and charge associated with the transition region in the current–potential curves for the formate decarboxylation. It is shown that this region corresponds to filling of the surface with adsorbed intermediates formed in the reaction. These observations are shown to support the reaction mechanism proposed in Part I.

ISSN:0008-4042    

DOI:10.1139/v63-007

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The hydrogen adsorption activities, per gram of nickel, of two nickel–magnesia catalysts are compared and explained on the basis of different types of nickel being present. The application of the Elovich equation to interpret the kinetic data shows the possibility of the presence of three kinetic stages in the temperature and pressure range studied. A study of the effect, on the hydrogen adsorption, of deliberate oxygen addition to and re-reduction of the catalyst surface shows that the nature of the oxygen contamination in the catalyst is different from that of the added oxygen.

ISSN:0008-4042    

DOI:10.1139/v63-008

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Xanthomegnin, a pigment isolated fromTrichophyton megnini, was shown to be (−) 3,3′-bis-[2-methoxy-5-hydroxy-7-(2-hydroxypropyl)-8-carboxy-l,4-naphthoquinone lactone]. Application of the Hudson–Klyne lactone rule (C. S. Hudson, J. Am. Chem. Soc.,32, 338 (1910); W. Klyne, Chem. Ind. (London), 1198 (1954)) gave results which supported the proposed stereochemistry.

ISSN:0008-4042    

DOI:10.1139/v63-009

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

SomeH0measurements in concentrated LiCl solutions are reported. It is shown that theH0values in 1–9 MLiCl, 1–9 MHClO4, and 1–11 MHCl solutions can be calculated using the equationwhereawis the activity of water,Cis either the molar or molal concentration, andnandBare least-squares constants. Values ofn = 2 (molar equation) andn = 1 (molal equation) fit the experimental data better than doesn = 4. With the molar equation a non-integral value ofnfor HClO4is required to give reasonableH0values. The adequacy and significance of integral and non-integral values ofnare considered. The nature of the constantBis also discussed. A more general equation is developed which under certain conditions reduces to the simpler equation. The more general equation is based upon a model which assumes the existence of more than one hydrated form of the indicator base, its conjugate acid, and H3O+. Some of the implications of this more general equation are considered

ISSN:0008-4042    

DOI:10.1139/v63-010

出版商:NRC Research Press    

年代:1963

数据来源: NRC