摘要:

The proton magnetic resonance spectra of dimethylthallium ion has been studied in both anionic and cationic detergent nematic phases. The spectra were analyzed to derive the values of inter- and intramethyl proton–proton dipolar coupling and the intermethyl scalar coupling constants. The degree of orientation of the dimethylthallium cation is much higher in the anionic nematic phase than in the cationic phase. It is proposed that electrostatic interactions play a significant role in the orientation of complex ions in ionic detergent nematic phases.

ISSN:0008-4042    

DOI:10.1139/v75-022

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The influence of substituents on the conformational properties ofN-substituted 5,6-dihydro-7H,12H-dibenz[c,f]azocines and their conjugate acids was studied by n.m.r. spectroscopy. The position of the equilibrium between a rigid boat-chair and a flexible twist-boat conformation has been measured. The twist-boat conformation in deuterochloroform increased as the size of the substituent increased. However, the effect was opposite for the series of conjugate acids in trifluoroacetic acid.A number of inversion barriers for theand theequilibria in CDCl3and TFA were determined. It was found that all barriers to interconversion were raised on protonation. The barrier to racemization for the twist-boat form of the quaternary methiodide of1was found to be >18 kcal/mol.

ISSN:0008-4042    

DOI:10.1139/v75-023

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Cobalt(II), nickel(II), copper(II), and copper(I) acetate, perchlorate, and tetrafluoroborate complexes with thiazolidine-2-thione, thiomorpholin-3-one, and thiomorpholin-3-thione have been prepared. On the basis of infrared and far infrared spectra, electronic spectroscopy, magnetism, and molecular conductance, the stereochemistries of these complexes were identified. Assignments for the metal–ligand modes have also been made. By the use of infrared spectroscopy it has been possible to distinguish whether or not the polyanions present in the complexes are coordinated to the transition metal ion or are present as free ions. Spectroscopic parameters for the complexes have been calculated and compared with similar chromophores containing sulfur, oxygen, and nitrogen donor atoms.

ISSN:0008-4042    

DOI:10.1139/v75-024

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The13C nuclear magnetic resonance parameters for a series of transition metal carbene complexes of the typetrans-[(CH3)Pt(As(CH3)3)2(p-XC6H4NH(CH3)C)]+PF6−are presented. Comparisons of the σ+substituent constants for —X with the carbene carbon shieldings reveal that both σ and π interactions are occurring between the aromatic rings and the carbene carbons. A quantitative inverse relationship between these carbene carbon shieldings and those of analogous phenylthiocarbene complexes is discussed. The phenyl rings are shown to adoptcisorientations with respect to the carbene methyl groups.

ISSN:0008-4042    

DOI:10.1139/v75-025

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The crystal structure of the synthetic intermediate, 9-cyano-1,10-dimethyl-6-ethy]enedioxy-1-octalin, C15H21O2N, was solved by direct methods. The compound crystallizes in the space groupp21/cwith cell dimensionsa = 12.282(4),b = 7.144(3),c = 15.619(5) Å, β = 104.04(1)°. Refinement was carried out isotropically for hydrogen and anisotropically for non-hydrogen atoms using full matrix least squares to anR-value of 0.043 for 1669 observed reflections.This compound, which has acisconfiguration at the octalin ring junction, is a precursor to a moiety of the alkaloid thelepogine. Thecisconformation is essential for total synthesis of thelopogine by this route.

ISSN:0008-4042    

DOI:10.1139/v75-026

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The cycloaddition of chloroketene acetals to α, β-unsaturated aldehydes and ketones gives the corresponding 2,2-dialkoxy-3-chloro-3,4-dihydro-1,2-pyrans. Treatment of these compounds with alkoxides in dimethylsulfoxide or dimethylformamide yields α-pyrones directly. Some intermediates and by-products have been identified and the reaction conditions have been studied.

ISSN:0008-4042    

DOI:10.1139/v75-027

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A simple one-step synthesis of α-pyrones and 3-chloro-α-pyrones from β-functionalized α, β-enones and ketene acetals has been devised. The method has also been adapted to the preparation of some 4-methoxy-α-pyrones. Finally the mechanism of the reaction has been investigated.

ISSN:0008-4042    

DOI:10.1139/v75-028

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

2,5-Dihydrothiophenes are dehydrogenated to thiophenes in high yield using chloranil intert-butanol or pyridine. The presence of a fully substituted carbon atom blocks the reaction. The method allows a flexible regiospecific synthesis of thiophenes in high yield from readily available starting materials.

ISSN:0008-4042    

DOI:10.1139/v75-029

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Deuterium exchange occurs at five β positions in fenchone under homoenolization conditions (t-BuO−–t-BuOD, 185°), C-6(exoandendo), C-8, C-9, and C-10. Both13C and2H n.m.r. methods were employed to monitor deuterium incorporation and the particular advantages of the latter are illustrated. The relative rates of the five exchange processes were determined directly by2H n.m.r. in contrast to the earlier homoenolization studies for which the stereoselectivity of exchange was established indirectly. The intermediate homoenolate ion can lead to rearrangement and the rearrangement products have been characterized by13C n.m.r. as the 3,3,6-trimethyl-norcamphors. Homoenolization of this mixture gave further evidence on the stereochemistry of homoenolate formation.

ISSN:0008-4042    

DOI:10.1139/v75-030

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The rate of exchange of methylene protons in creatinine has been followed in D2O by means of proton magnetic resonance spectroscopy over a range of acidity from pD12.22 toDA–4.24. A plot of the logarithm of the rate against acidity function is in the form of a "W", one wing of which involves reaction of neutral creatinine with hydroxide ion, and the other diprotonated creatinine with water. The central peak represents reaction of protonated creatinine with a molecule of creatinine acting as base. The reaction is subject to catalysis by buffers.The activation of exchange produced by protonating the substrate is designatedprotonactivatingfactor, p.a.f., and factors affecting its size are discussed in terms of structure.

ISSN:0008-4042    

DOI:10.1139/v75-031

出版商:NRC Research Press    

年代:1975

数据来源: NRC