摘要:

The use of interferometry to make visible concentration gradients at working electrodes has progressed to video tape recording of interferograms. Rapid accurate analysis should be able to gain sufficient data from experimental runs where migration effects are just balanced by diffusion effects to help evolve a better mathematical formula with which to predict concentration changes at working convectionless electrodes. Data are presented showing a quasi-steady state polarization in a low current density electrolysis run with Fe2+the electroactive species.

ISSN:0008-4042    

DOI:10.1139/v78-096

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A model of the oxide–electrolyte interface is proposed which accounts both for the Nernstian behaviour of the oxide (glass) electrode and the anomalous capacitance values of some oxides defined in terms of the change in surface charge with pH. The essential feature of the model is the existence of a transition layer of atomic dimensions in thickness within which is established an equilibrium between oxide and aqueous ionic species. The Nernstian behaviour of the oxide (glass) electrode is independent of the model chosen for the oxide–electrolyte double layer but requires that the oxide be conducting; the capacitance of the system, of course, is dependent on the detailed structure of the interface.

ISSN:0008-4042    

DOI:10.1139/v78-097

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The effect of varying the applied potential during progressive three-dimensional nucleation and growth is described. The assumed model is that due to Armstrong, Fleischmann, and Thirsk in which expanding nuclei are considered to be right circular cones distributed at random on the electrode surface. The present work extends the previous potentiostatic approach by considering that the electrode surface coverage function responds instantaneously to small changes of applied potential. Under these circumstances we show that it is possible to calculate in an exact way the theoretical response of the model to various applied potential waveforms. In particular, the linear potential sweep and the staircase potential ramp are considered, as well as feedback loops generated by uncompensated ohmic overpotential. Certain limiting cases are derived which may be tested by experiment.

ISSN:0008-4042    

DOI:10.1139/v78-098

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Some oxidations and reductions of 4-hydroxy-6-methyl-2-pyridones are discussed. A remarkable reduction–cyclization of 4-hydroxy-3-(1′-hydroxy-2′-oxopropyl-)-6-methyl-2-pyridone (2b) produces the novel system10a.

ISSN:0008-4042    

DOI:10.1139/v78-099

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The acid-catalysed reaction of furan with acetone has been investigated for the presence of intermediates by vapour phase chromatography of the reaction mixture. It has been shown that 2-furyl-2-propene is a component of the furan–acetone reaction mixture. Other possible intermediates have been prepared and their reactions investigated. It is our conclusion that the alcohol, 2-furyl-2-propanol, is the initial intermediate in the condensation reaction. We have also reexamined some reactions between furan and cyclohexanone reported by other investigators.

ISSN:0008-4042    

DOI:10.1139/v78-100

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The synthesis of the sequential polypeptides (N-δ-Z-L-Orn-γ-BzI-L-Glu)nand (N-δ-Z-L-Orn-β-BzI-L-Asp)nby solution methods is described. Both polypeptides are α helical in chloroform as shown by circular dichroism. However, the conformation in this solvent is rather fragile, since small additions of TFA to a dilute solution of the polypeptides in chloroform is sufficient to cause the helix-to-coil transition, as demonstrated by cd and nmr. It is postulated that the low stability of the helical conformation is attributed, in this case, to a cooperative collapse of the ordered conformation.

ISSN:0008-4042    

DOI:10.1139/v78-101

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The gas phase decarboxylations of 1-naphthyl-, 2-naphthyl-, and 9-phenanthrylacetic acids all proceed through a homolytic pathway. There is no evidence for the concerted 1,5-hydrogen shift usually encountered in the decarboxylation of β,γ-unsaturated acids.

ISSN:0008-4042    

DOI:10.1139/v78-102

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

2,6-Dimethyl-1,2-dihydroquinoline has been isolated as an intermediate in the Doebner-Miller synthesis of 2,6-dimethylquinoline. Dihydroquinolines may be efficiently prepared by the acid catalysed elimination of water from a 4-hydroxy-1,2,3,4-tetrahydroquinoline. The analogous 4-phenylamino derivatives also undergo facile elimination of the benzylic amino group under similar conditions.

ISSN:0008-4042    

DOI:10.1139/v78-103

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Curves of the water activity coefficient γwhave been obtained as a function of water mole fraction in the mixtures AgNO3 + TlNO3 + Cd(NO3)2 + H2O at 98.5 °C. It has been shown, in this study, from the BET equation itself and verified experimentally, that γwmay pass through an extremum value for certain systems. The position of such an extremum near the fused salt end of the concentration scale can explain the appearance of a 'practical' Henry's law in a finite concentration range. The curves of the excess free energy of the system undergo rather unusual changes of shape as the cadmium content of the melt is varied.

ISSN:0008-4042    

DOI:10.1139/v78-104

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The aminosugar 4-deoxy-D,L-daunosamine and its derivatives were synthesized starting with 2,4-pentanedione which was converted to the key intermediate oxazolino-α-pyrone (19) by enamine formation with morpholine, oxidation with benzoyl peroxide, condensation with ammonium acetate, bromination withN-bromosuccinimide, nitrile formation, acid hydrolysis, and cyclization with thionyl chloride. Hydrogenation of19gave the δ-lactone22which was converted to 4-deoxy-D,L-daunosamine derivatives by reducing the lactone ring to the corresponding hemiacetal26.

ISSN:0008-4042    

DOI:10.1139/v78-105

出版商:NRC Research Press    

年代:1978

数据来源: NRC