摘要:

A facile synthesis ofN-acyl-1,3-oxathiol-2-imines,7, is reported. It comprises the reaction ofO-alkyl acylcarbamothioates,4, with 2-chloroketones in the presence of alcoholic sodium alkoxide. The resultingO-alkyl-S-substituted-N-acylcarbonimidothiates,6, undergo cyclization with elimination of alcohol, spontaneously, or upon heating in boiling toluene to form7.

ISSN:0008-4042    

DOI:10.1139/v81-229

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Ultraviolet spectra ofN-tert-butylbenzamide taken in 0–92% sulfuric acid solutions clearly show that two processes, having roughly equal effects on the spectra, take place over this acidity range. One is protonation of the molecule, and the other is either tautomerization from N- to O-protonated forms, or a pronounced medium effect on the latter. Attempted separation of these two processes using characteristic vector analysis fails. However, separation is possible using an analysis based on the excess acidity (X-function) method. This shows that the second process is a medium effect. The analysis permits accurate calculation ofandm*values in the presence of medium effects on the acid form, the base form, or both.

ISSN:0008-4042    

DOI:10.1139/v81-230

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Protonation acidity constants for 27 benzamides, acetamides, and lactams have been determined. Ultraviolet, and13C and1H nmr, spectroscopic methods were used; almost all the spectra were found to be subject to medium effects, some quite severe, as the sulfuric acid concentration was increased. Despite this, the excess acidity (X-function) method gave accurateandm*values. In all cases protonation, followed by a medium shift in the spectrum of the protonated form, was the only process taking place; protonation was essentially complete in 60% H2SO4. The results for the different bases are interpreted in terms of the resonance, inductive, and steric effects in operation in the acid and base forms.

ISSN:0008-4042    

DOI:10.1139/v81-231

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The specificity of horse liver alcohol dehydrogenase (HLADH) with respect to unsubstituted five-, six-, and seven-membered ring 3- and 4-thiaketone and -thiaalcohol substrates has been examined. The enzyme is found to have a broad tolerance of the structural variations within this series. HLADH also exhibits encouraging (up to 46%) enantiotopic and enantiomeric specificity in preparative-scale reduction and oxidation reactions of the heterocyclic ketones and alcohols respectively.

ISSN:0008-4042    

DOI:10.1139/v81-232

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Niobium–cobalt alloys are stable to corrosion in an open circuit in the presence of oxygen in 25% KOH solution as long as the weight percentage of cobalt exceeds 50%. Below this value, samples submitted to these conditions disintegrate after 30 days. When these alloys are submitted to anodic polarization an active dissolution is noted followed by passivation and in the presence of cobalt production of oxygen occurs. Electronic Auger Spectroscopic (EAS) analysis of pure niobium and its alloys with 30% and 90% cobalt indicates that the oxide film grows in an irregular manner according to the nature of the surface. Thus, for an identical anodic polarization (0.845 V vs. ENH for 6 hours) the oxide film changes from 4.13 × 10−2 μm for pure Nb to 0.10 μm for the 30% Co–Nb alloy and becomes as thin as 8 × 10−4 μm for the 90% Co–Nb alloy. The concentration profile as shown by EAS indicates a preferential dissolution of Nb over Co in the oxide film. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v81-233

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Iodine-129 Mössbauer data for SnI4, MeSnI3, Me2SnI2, Me3SnI, Me3SnI2−, Me3SnI.py, and Me2SnI2.2py are reported. The data are compared with available nqr data for the corresponding chlorides and bromides. The Mössbauer data are interpreted as evidence that MeSnI3, Me2SnI2, and Me3SnI are distorted from tetrahedral geometry in the solid state. The applicability of the additive model in interpreting119Sn quadrupole splittings in these compounds is commented on.

ISSN:0008-4042    

DOI:10.1139/v81-234

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A measurement of equilibrium [4]:t-C4H9+ + BzCl = t-C4H9Cl + C7H7+led to equilibrium constantsK4which are in fair agreement with earlier work by Abboudetal. However, the present temperature dependence predicts a ΔS40which is sufficiently different from that by Abboudetal. to put in question the indentification of C7H7+as Bz+on the basis of the measured ΔS40value. Therefore experiments were made to confirm that C7H7+produced in [4] is Bz+and not the tropylium cation. A C7H7+cation was produced by hydride abstraction from 1,3,5-cycloheptatriene. The behaviour of that C7H7+ion was entirely different from C7H7+produced by chloride abstraction from BzCl or hydride abstraction from toluene. While the benzyl derived C7H7+engaged in a number of reactions like hydride abstraction, chloride abstraction, addition, condensation, etc., the C7H7+from the heptatriene remained completely unreactive. On this basis the C7H7+ions were identified as Bz+and tropylium+, respectively. Rate constants for several reactions of Bz+were determined. It is concluded that a rearrangement from benzyl to tropylium cations and vice versa does not occur at least up to 300 °C. The ions also retain their identity if they are produced with considerable internal excitation energy.

ISSN:0008-4042    

DOI:10.1139/v81-235

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Solutions of aqueous sodium 7-2H-cholate have been studied as a function of cholate concentration by2H nmr. Relaxation times and solution viscosities have been used to show that cholate is monomeric in solution at 0.1 M. Increasing concentration leads to tetramer formation which is complete at 0.1 M. The tetramer solutions are stable up to 55 °C. Solutions of cholate in aqueous pyridine also form tetramers in the same fashion. Evidence was found, however, for a weak hydrogen bonding interaction between the two.

ISSN:0008-4042    

DOI:10.1139/v81-236

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The quantum yields for photolysis of 0.25 Msolutions of bicyclo[3.1.0]hexan-3-one, 1,5-dimethylbicyclo[3.1.0]hexan-3-one, and tricyclo[4.3.1.0]decan-8-one in pentane or cyclohexane with 313 nm light are 0.44, 0.52, and 0.32, respectively.

ISSN:0008-4042    

DOI:10.1139/v81-237

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The complexes [Ni(III)(LL)3](ClO4)3(LL = phen, bipy, and substituted derivatives) have been isolated as products of the electrolysis in acetonitrile of the corresponding nickel(II) species. Electron spin resonance measurements for all nickel(III) species in frozen anhydrous CH3CN and in frozen 4.0 M HClO4solutions (77 K) show a single near symmetric line shape (g ≈ 2.10) with fine structures appearing only in the presence of mixed solvent systems. In a CH3CN/5% H2O glass (77 K) quintets in theandregions are observedconsistent with Jahn–Teller distortion expected for a low-spin d7system. Ultraviolet–visible spectra are also reported. Electrode potentials for the Ni(LL)33+/2+couples in CH3CN (0.1 M NaClO4) lie in the range 1.51 V (Ni(4,4′-Me2bipy)33+) to 1.82 V (Ni(5-NO2-phen)33+) and the powerful oxidizing nature of these species has been confirmed in reaction with both organic and inorganic substrate

ISSN:0008-4042    

DOI:10.1139/v81-238

出版商:NRC Research Press    

年代:1981

数据来源: NRC