Proton magnetic resonance studies of 8-hydroxyquinoline derivatives

The PMR spectra of 8-hydroxyquinoline and eighteen derivatives have been obtained at 220 MHz. For several of the compounds, PMR spectra have not been reported previously. The use of 220-MHz frequency considerably facilitates the interpretation of spectra from such complex derivatives as 2-(2'-pyridyl) and 2-(2'-thienyl)-8-hydroxyquinoline.     

Proton magnetic resonance studies of actinomycin-related peptides containing N-methyl groups

The PMR spectra of several cyclic and acyclic dipeptide derivatives representing portions of the actinomycin structure have been studied. In the spectra of the acyclic compounds temperature-dependent duplicity resulted from the equilibration of conformers possessing cis and trans peptide bonds. The lanthanide shift reagent Eu(FOD)₃ was utilized to distinguish N-methyl groups in the two conformations and observations were made on the steric dependence of the observed shifts. The origin of the wide variation in chemical shift of N-methylvalyl α-protons is discussed in relation to the conformation of actinomycin.     

Proton and boron-11 magnetic resonance studies of some potassium tetraarylborates

Proton and boron-11 magnetic resonance spectra for several potassium para-substituted tetraarylborate compounds [KB(C₆H₄-pX)₄, where X is H, OCH₃, CH₃, Br, Cl, F, CF₃] have been obtained. The chemical shift between the centers of the AA′ and XX′ multiplets for the ring proton multiplets, relative to a reference chemical shift of 0·39 ppm for potassium tetraphenylborate, correlated with the corresponding Hammett σ values for the para-substituent. Additionally, the boron-11 chemical shifts gave a good correlation with corresponding σ values for the substituents. Electronegativities of para-substituted phenyl rings were calculated and found to be approximately 2·70 for all compounds studied. It was shown that electronic substituent effects do not greatly influence the electron density surrounding the central boron atom in the tetraarylborate ions.     

13C nuclear magnetic resonance studies on some substituted isoxazoles

¹³C n.m.r. spectra of some substituted isoxazoles have been examined to ascertain the reactive site in the metallation of 4-substituted 3,5-dimethylisoxazoles. The results obtained indicate that metallation occurred exclusively at the C-5 methyl.     

Proton magnetic resonance studies of the phase structure of bulk-crystallized linear polyethylene

The broad-line proton NMR spectra of melt-crystallized samples of polyethylene covering a very wide range in molecular weight have been analyzed in terms of contributions from three components: (1) a crystalline region with crystals of orthorhombic form; (2) a noncrystalline region with liquid-like character which produces a Lorentzian contribution to the spectrum; and (3) an intermediate region in which the rotation of methylene groups about C—C bonds is partly hindered. The relative mass fractions as well as the character of these components depend greatly on the molecular weight. Samples of low molecular weight (e.g., ?30,000) are predominantly composed of lamellar crystalline regions with a minor amount of interfacial regions and no liquid-like interzonal regions. As the molecular weight increases beyond 45,000, an interzonal region with a liquid-like character associated with a higher molecular mobility is produced. Above a molecular weight of 100,000, this liquid-like character becomes pronounced with an increase in molecular mobility in the interfacial region.     

Proton magnetic resonance spectra of cinnolines

The ¹H NMR spectra of cinnoline and some 8-substituted derivatives 1 in DMSO-d₆ are reported. A previous assignment of the chemical shifts of the heterocyclic ring protons H-3 and H-4 is confirmed by deuteration studies. The variations in the chemical shifts of H-3 to H-7 are discussed in terms of (a) solvent effects, (b) the perturbation effect of the heterocyclic ring, and (c) the electronic and proximity effects of the 8-substituents, using single-parameter (SCS_o, SCS_m, SCS_p, σ_o, σ_m, σ_p, σ_p⁺, σ_4,1, σ_5,1, σ_6,1Q) and dual-parameter (F, R; σ₁,σ_R) treatments to correlate the data. Marked proximity effects on H-7 are noted for the nitro and acetamido groups, and are correlated with conformational changes due to interaction of the groups with the N-1 lone pair. Variations in the coupling constants are attributed to partial double-bond fixation.     

13C Nuclear magnetic resonance studies of some substituted thiols and thioanisoles

¹³C NMR spectra of thiophenol, 4-nitrothiophenol, 4-X-thioanisole (X = NO₂, NH₂, SH, H) were examined in CDCl₃ solution. Substituent chemical shift values (additivity parameters) for the −SH and −SCH₃ groups are reported.In para-substituted thioanisoles, while the −NH₂ group caused a deshielding and −NO₂ a shielding of SCH₃ carbon resonance, −SH appeared to have had no effect on the carbon resonance.     

Ring-chain tautomerism of substituted hydrazones

The reaction of -(N-tert-butylhydrazino)alcohols with acetone and acetaldehyde leads to the formation of 4-tert-butylperhydro-1,3,4-oxadiazines. The tautomeric equilibrium between the latter and the corresponding N-tert-butyl-N-(-hydroxyalkyl)hydrazones is displaced strongly in the direction of the cyclic form. The PMR spectra of the majority of the perhydrooxadiazines obtained show that they exist in the chair conformation with practically no deformation in the N-C-C-O region. However, for the 2,2,6,6-tetramethyl derivative two nonchair (probably twist) conformations are preferred.For Communication VI, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1461–1468, November, 1973.     

Ring-chain tautomerism of substituted hydrazones

It is shown that 5,6-dihydro derivatives are formed as a result of the oxidation of 2-unsubstituted or 2-monosubstituted perhydro-1,3,4-oxadiazines with yellow mercuric oxide.See [1] for communication X.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1208–1211, September, 1978.     

Proton magnetic resonance spectra of monosubstituted naphthalenes

The chemical shifts and coupling constants for the ring protons of fourteen monosubstituted naphthalenes in carbon tetrachloride solution have been obtained by analysis and computer simulation of their 100 MHz magnetic resonance spectra. Studies at several concentrations have enabled shifts extrapolated to infinite dilution to be obtained and concentration effects arising from solute–solute interactions to be determined.