摘要:

Various alkylbenzene-based electrolytes used in the electrolytic reduction of aluminum were analyzed by gas phase chromatography. Neither oxidation nor reduction products could be detected in the usual electrolysis conditions. Solvents such as toluene, ethylbenzene, or diethylbenzene undergo dismutation reactions in the presence of aluminum bromide. With or without electrolysis, electrolytes based on 1:1 ethylbenzene/toluene and 1:4 diethylbenzene/toluene tend toward nearby equilibrium compositions. This fact explains why electrolytic aluminum coatings of similar quality are obtained.The effect of water content on the quality of aluminum coatings obtained by electrolytic reduction was studied. The study revealed that better coatings are obtained if the organic solvents are used 'as received'. Thus it was possible to avoid the pretreatments of drying or hydrating these solvents. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v78-389

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Using a computer-controlled precision polarograph the formation constants of electron donor–acceptor (EDA) complexes formed from aromatic hydrocarbons and nitrofluorene derivatives have been determined in acetonitrile. The EDA interactions are of the same magnitude in this solvent as in less polar solvents. The strength of the complexes is related to the reduction potential (or electron affinity) of the acceptors and the size of the π system of the donors. Spectra of the complexes were computed from spectra of mixtures of accepter and donor with the help of the polarographic data. No relationship between the molar absorptivity of the charge-transfer band and the formation constant was apparent from these spectra.

ISSN:0008-4042    

DOI:10.1139/v78-390

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

In the low density vapors the density normalized mobilities μnof thermal electrons decreased in the ordern-hexane > cyclopentane > cyclohexane, although the differences were only ∼ 10%. The mobilities began to increase at electric field strengthsE/n > 0.4 Tdin cyclopentane, > 0.5 Tdin cyclohexane and remained independent of field strength up to 1.5 Tdinn-hexane. The ratio of the threshold drift velocity for electron heating to the speed of low frequency sound in the gas, υd(threshold)/c0 = 11 in cyclopentane, 14 in cyclohexane, and is > 35 inn-hexane; it increases with decreasing sphericity of the molecules. The electrons are cooled mainly by inelastic collisions with the hydrocarbon molecules. The temperature coefficients of mobilities in the low density gases increase as the molecules become more globular, which could reflect the participation of either low lying transient negative ion states or a Ramsauer–Townsend effect in the scattering processes. The normalized mobilities μnin the saturated vapors began to decrease atn = 4 × 1019 molecules/cm3inn-hexane, 13 × 1019in cyclohexane, and 30 × 1019in cyclopentane. It appears that the minimum size of molecular cluster required for electron quasilocalization is smaller inn-hexane than in cyclohexane, and larger in cyclopentane. Electron localization interactions are weaker for more globular molecules.Mobilities in the critical fluids were 16 cm2/V s inn-hexane, 23 in cyclohexane, and 22 in cyclopentane.Mobilities in the liquids were independent of field up to the highest value used, which was 1.5 Tdin the hexanes and 0.9 Tdin cyclopentane. The mobilities and their temperature dependences were interpreted in terms of a model

ISSN:0008-4042    

DOI:10.1139/v78-391

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The general usefulness of phenyl phosphorodichloridate (PPDC) in the synthesis of non-nucleoside cyclic phosphates is described. The method is illustrated with several examples including cyclic phosphates incorporating six to nine members. However, the reagent could not be used for the preparation of five-membered cyclic phosphates or 3′,5′-cycloadenylic acid (cAMP) from adenosine. Based on a number of observations, the conclusion was reached that PPDC cannot be used for the synthesis of strained or reactive cyclic phosphates. A convenient synthesis ofcis- andtrans-2-hydroxycyclopentanemethanol and a simple, quantitative method of separation of the two isomers is described. A number of cyclic phosphates were tested as substrates and inhibitors for cyclic purine phosphodiesterase and protein kinase.

ISSN:0008-4042    

DOI:10.1139/v78-392

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

ESCA core line spectra have been obtained for uracil, the thiouracils, and some 1-methyl and 3-methyl analogues. In addition, anionsof the mono methyl derivatives have been prepared and studied. Core line binding energy shifts for all solid compounds, ionic and neutral, are found to correlate reasonably with CNDO/2 charge distributions calculated for the free molecules. The correlation line for ionic molecules is offset from that for neutrals by a constant factor ascribed to an intermolecular potential term. Specific effects of methylation, thionation, and ionization on the charge distribution are described. Methylation at either nitrogen leads to electron release from the nitrogen into the ring. Thionation results in a decrease in the charge at the site of thionation, while the electron density at adjacent atoms increases. The alterations in charge density are somewhat different for neutral and ionic compounds. Upon ionization of either N(1) or N(3) sites, much of the residual charge is located on the keto oxygens. The presence and position of the thionated carbon during ionization mainly affects the change in electron density at the C(6) position.

ISSN:0008-4042    

DOI:10.1139/v78-393

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The effect ofp-dioxane on the temperature of adiabatic compressibility minimum (TACM) and sound velocity maximum (TSVM) in water have been studied. Both the structural shifts, [ΔTβ str]expand [ΔTu str]exp, are found to be positive, increasing with concentration and reaching maximum values aroundThese results have been explained as due to the formation of hydrates of dioxane of varying composition indicating the existence of long range order in the water +p-dioxane System in the water-rich region.

ISSN:0008-4042    

DOI:10.1139/v78-394

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Antimony-121 Mössbauer spectra for [Sb2F42+][SbF6−]2and three compounds containing the [Sb3F14−] ion are reported. The Mössbauer data are discussed in relation to their known structures. Two of the compounds give spectra which, on analysis, give η values of unity.

ISSN:0008-4042    

DOI:10.1139/v78-395

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A reexamination of previous proposais for the prediction of regioselectivity in sulfide chlorinations has found them to be unsatisfactory. A new basis for such predictions is advanced viz. the electronegativity difference (ΔXp) of the substituents attached to the α- and α′-carbon atoms of the sulfide substrate. Upon establishing that the new basis for these predictions is satisfactory, it is successfully applied to the problem of predicting reactivity differences in isomeric sulfide chlorinations. The formation of isomeric sulfonium ions is used to establish the failure of possible isomerization processes to occur under normal reaction conditions.

ISSN:0008-4042    

DOI:10.1139/v78-396

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Syntheses which convert pyrromethenes, pyrromethanes, or pyrroles to porphyrins in one step are limited by the necessity of avoiding inseparable mixtures of products. Such mixtures from pyrromethenes or pyrromethanes may become separable, and those from pyrroles avoided, if the products bear appropriate negative substituents.It would appear that isomeric porphyrins with two negative substituents, on adjacent and on opposite rings, respectively, do not form mixed crystals (solid solutions) and are easily separated by crystallization.

ISSN:0008-4042    

DOI:10.1139/v78-397

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

One of the more convenient syntheses of porphobilinogen has been adapted to that of isoporphobilinogen and extended to the lactams of both. Aminomethylation of appropriate 2-free pyrroles by the Tscherniac-Einhorn method gives derivatives of porphobilinogen and isoporphobilinogen. A method for aminomethylating reactive pyrroles is illustrated by the conversion of 2,4-dimethylpyrrole into its 5-N-acetylthiocarboxamide, then into its 5-acetylaminomethyl derivative, using acetyl isothiocyanate then Raney nickel, both at ≤20 °C.

ISSN:0008-4042    

DOI:10.1139/v78-398

出版商:NRC Research Press    

年代:1978

数据来源: NRC