Deuteriochloroform Solution Research Articles

Photochemical reactions of N-(diphenylmethylene)methylthiomethylamine N-oxide. The diphenylmethylene(methylene)amine N-oxyl radical

U.v. irradiation of the title compound in carbon tetrachloride and deuteriochloroform solutions cleanly gave benzophenone and eventually, but less cleanly, dimethyl disulphide. Initial homolysis gave the diphenylmethylene(methylene)amine N-oxyl radical which was detected and identified by e.s.r. spectroscopy. A second radical, possibly the methylthiyl radical, was observed. Subsequent reactions gave benzophenone and N-methylthiomethyleneamine, which in turn, photochemically and thermally, gave dimethyl disulphide and polymeric materials that in part involved chlorine abstraction from the solvent. The well-resolved e.s.r. spectra of the nitroxide radical have been analysed, and splitting constants have been assigned, by comparison with the spectra of partially and fully deuteriated nitroxides.

Un Exemple de L'Utilisation des Complexes Paramagnétiques Dans les Études Conformationnelles

AbstractWe have deduced the most probable conformation for 4‐cycloheptene carbinol‐8d2 in deuteriochloroform solution from coupling constants and paramagnetic shifts induced by Eu(DPM)3.

Nuclear magnetic resonance specroscopy. Proton spectra of 2-pyridones

The proton magnetic resonance spectra of 2-pyridone, 1-methyl-2-pyridone, and 1-(2'-pyridyl)-2-pyridone in deuteriochloroform solution were recorded at 100 and 220 MHz. A computer-assisted analysis of these spectra yielded the chemical shifts and consistent sets of coupling constants. Some regularities in the effects of structure and concentration on the chemical shifts were observed. The spectra of 2-pyridone in deuterium oxide and benzene were briefly explored.

Studies on benzimidazoles. Part VIII. 1H nuclear magnetic resonance study of substituted 2-chloro-1-methylbenzimidazoles

A number of benzo-substituted 2-chloro-1-methylbenzimidazoles has been studied by 1H n.m.r. spectroscopy. It is observed both from the ring and N-methyl proton chemical shifts measured in deuteriochloroform and trifluoroacetic acid solution that conjugation effects are present between substituents and the nitrogen atoms of the heterocyclic ring. Proton–proton coupling constants can be rationalized in terms of additive substituent effects when there are no strong mesomeric interactions between substituents and the heterocyclic ring. Charge densities have been calculated for both σ and π-electrons, and the correlations between charges and chemical shifts show that the substituents also perturb the heterocyclic ring through the σ-skeleton.

Correlation of the intramolecular nuclear Overhauser effect with internuclear distance

A linear relationship between the intramolecular nuclear Overheauser effect (n.O.e.) and the sixth power of the internuclear distance for protons in reasonably compact organic molecules in deuterio-chloroform solution is derived. Examples of H—H and CH3—H interactions from this work and the literature have been used to demonstrate the validity of this relationship. It is shown that application of the observed n.O.e. between two protons or between a proton and a methyl group can be used to determine internuclear distances in unknown structures.

Conformations and configurations of some chlorosulfated α- and β-D-pentopyranosyl chlorides

The conformations of the fully chlorosulfated α- and β-D-xylopyranosyl and lyxopyranosyl chlorides in deuteriochloroform solution have been studied by proton magnetic resonance spectroscopy. The analysis of the spectra indicated that the anomeric effect is a factor in determining the conformational preference of the pentopyranosyl chlorides, as each existed predominantly in the conformation in which the chlorine was axial. A number of factors involving the synthesis of these chlorides have also been elucidated.

Reactions of phosphines with acetylenes. Part VII. Structure revision of a rearranged 1:2 adduct of triphenylphosphine and dimethyl acetylenedicarboxylate. A stable 2H-phosph(V)ole

Triphenylphosphine and dimethyl acetylenedicarboxylate (2 equiv.) react to form a yellow adduct, which has been shown to be the stable 2H-phosph(V)ole (10a) rather than an open-chain phosphine as previously postulated. Tri-p-tolylphosphine gives a similar yellow adduct (10b). The temperature-dependent 1H n.m.r. spectra of the adducts in deuteriochloroform solution and in trifluoroacetic acid solution display features characteristic of phosphoranes stabilised by alkoxycarbonyl groups. Treatment of the adduct with zinc and acetic acid gave the open chain phosphine oxide (12). The infrared spectra of allylidenephosphoranes stabilised by methoxycarbonyl groups are discussed.

Reactions of phosphines with acetylenes. Part IV. A stable 1,2-diphosphorane. Restricted rotation in a stable alkylidene diphosphorane

The reaction of dimethyl acetylenedicarboxylate with an excess of triphenylphosphine gives a stable 1,2-diphosphorane whose structure [Ph3P:C(CO2Me)·C(CO2Me):PPh3] has been proved by a combination of physical and chemical methods. The n.m.r. spectrum of the diphosphorane at room temperature in deuteriochloroform solution establishes the compound to exist as a mixture of three slowly interconverting conformers, in which there is an energy barrier to rotation about the bond between the ester carbonyl carbon atom and the adjacent carbon atom. Dimethyl acetylenedicarboxylate and diphenylmethylphosphine give an analogous 1,2-diphosphorane with similar properties.

The stereochemistry and conformation of (±)-6a,12a-dihydrorotoxen-12(6H)-one and natural rotenoids from spin-coupling considerations

The thermodynamically stable form of 6a,12a-dihydrorotoxen-12(6H)-one is shown to be the cis-form by analysis of the spin-coupling of the protons attached to C-6, C-6a, and C-12a. Assignments are confirmed by deuteration and by examination of the 6,6-dimethyl derivative and enable the probable ring-B conformation in deuteriochloroform solution to be determined. Masking of the multiplets by other groupings occurs in rotenone and some natural rotenoids, but in suitable solvents elliptone can be analysed, confirming the cis-B/C fusion allotted to natural rotenoids on other grounds. The α-orientation of the hydroxyl grouping resulting from borohydride reduction of a cis-B/C rotenoid is also supported by n.m.r. results.