Proton magnetic resonance spectra of some disubstituted naphthalenes

The chemical shifts and coupling constants for the ring protons of nine disubstituted naphthalenes (mainly halogenonitre compounds) in carbon tetrachloride solutions have been obtained by analysis and computer simulation of their 100 MHz magnetic resonance spectra. Substituent effects are essentially additive except when a strong π-donor group is in direct conjugation with a strong π-acceptor group.     

Proton magnetic resonance spectra of some silyl-substituted ethylenes

Conclusions The PMR spectra of a number of silyl-substituted ethylenes were obtained. An explanation was given for the positions of the resonance lines of the olefinic protons.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 875–876, April, 1971.     

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 tautomerism in substituted pyrimidines

Studies of line width and chemical shift vs. temperature for amide and hydroxyl proton magnetic resonance signals from: barbituric acid, dialuric acid, parabanic acid, alloxan and alloxan monohydrate dissolved in anhydrous dimethyl sulfoxide-d₆ are reported. The behavior of the amide signals shows that, between 20 and 65°C, none of the compounds listed exhibits lactim-lactam tautomerism. The amide proton resonance in uracil has also been investigated. The signal is a closely spaced, equal intensity, doublet due to the non-equivalence of H(1) and H(3). Again, no evidence of tautomerism is observed. Activation energies for the hydroxyl resonances in dialuric acid and alloxan monohydrate indicate hydrogen bonding between solute and solvent. The results of simple LCAO-MO calculations are in accord with the experimental conclusions concerning tautomeric equilibria.     

Proton magnetic resonance spectra and conformation of some trisubstituted cyclopropane compounds

The n.m.r. spectra of some 1,2,2-trisubstituted cyclopropanes are reported. Coupling constants and chemical shifts of the cyclopropane protons and their dependence on substituent effects are discussed. Conformations of benzylcyclopropane derivatives are investigated by long range magnetic shielding. The concentration dependence of the n.m.r. spectra of some 1,3-diols is explained by inter- and intramolecular hydrogen bonding.     

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.     

Synthesis of some halogenated tetraarylborates

The reactions of 3,4-dichlorophenylmagnesium bromide and 3,5-dichlorophenylmagnesium bromide with B(OEt)₃ and NaBF₄ were studied The corresponding tetraarylborates [(3,4-Cl₂C₆H₃)₄B]NH₄ and [(3,5-Cl₂C₆H₃)₄B]Na were obtained and characterized. The significant influence of the substituents inductive effect on the reaction course was revealed. NaBF₄ was found to be a valuable boron reagent in the synthesis of tetraarylborates containing highly electronegative substituents. The molecular structure of [(3-CF₃C₆H₄)₄B]NH₄ obtained from the reaction of 3-trifluoromethylbromobenzene with NaBF₄ and Mg was determined using X-ray analysis.     

Proton magnetic resonance spectra of some vinyl and ethyl derivatives of five-membered N-heterocycles

Conclusion On the basis of the chemical shifts of the signals in the PMR spectra of the N-vinyl and N-ethyl derivatives of indole, benzimidazole, benzotriazole, and imidazole a theory was advanced regarding the character of the influence of a second and third nitrogen atom on the vinyl and ethyl radicals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 475–476, February, 1972.We express our gratitude to Yu. L. Frolov for his helpful evaluation of the experimental data.     

Naphthopyrones,Part I Proton magnetic resonance spectral studies of some methylnaphthopyran-2-one and methylnaphthopyran-4-one derivatives

The 220 MHz¹H-NMR spectra of four methylnaphthopyrone derivatives are presented and discussed. The chemical shift changes which occur upon protonation in trifluoroacetic acid solution are much more significant for the benzochromones than for the benzocoumarins. The particularly large effects at the methyl (0.6 ppm) and at the residual pyrone ring proton (1.2 ppm) provide a useful technique for differentiation between the two series of compounds.

---

Naphthopyrone, 1. Mitt.:¹H-N M R einiger Methylnaphthopyran-2-one und Methylnaphthopyran-4-one

Zusammenfassung Es werden die 220 MHz¹H-NMR-Spektren von vier Methylnaphthopyronen diskutiert. Die Änderungen der chemischen Verschiebungen, die sich mit Trifluoressigsäure als Lösungsmittel ergeben, sind für die Benzochromone bedeutend signifikanter als für Benzocumarine. Die besonders großen Effekte für Methyl (0,6 ppm) und das verbleibende Pyronringproton (1,2 ppm) stellen eine brauchbare Methode für die Unterscheidung der beiden Reihen dar.

     

C-13 magnetic resonance studies of some papaveraceae alkaloids

The natural abundance ¹³C magnetic resonance spectra of some Papaveraceae alkaloids have been determined at 22·628 MHz employing the pulse Fourier transform technique. Several techniques were employed to aid in spectral assignments and it has been possible to make self-consistent assignments for all the resonances for these alkaloids. Evidence is presented for trans-annular interaction between the amino group and the carbonyl group situated across the ten-membered ring.     

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.