Study of stereochemical dependences of the direct13C−1H spin-spin coupling constants in vinylpyridines by the quantum-chemical INDO-RPA method

The stereochemical dependences of the direct¹³C−¹H spin-spin coupling constants (SSCC) in the vinyl group of vinylpyridines studied by the quantum-chemical INDO-RPA method indicate that the steric closeness of the hydrogen atom to the nitrogen atom causes an increase in the corresponding direct¹³C−¹H SSCC and a decrease in the analogous constant of the geminal hydrogen atom. The results obtained qualitatively agree with the data ofab initio calculations for the simplest systems and the experiment. At the same time, an essential quantitative overestimation of the real effect takes place. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 265–267, February, 1997.     

Conformational analysis of N-vinyl-2-phenylpyrrole

A conformational analysis of N-vinyl-2-phenylpyrrole was undertaken according to the results from experimental measurements and nonempirical quantum-chemical calculation of the high-level ¹³C–¹H and ¹³C–¹³C spin-spin coupling constants. Angular relationships were established in the direct and vicinal J _C,C and J _C,H constants in the N-vinylpyrrole fragment, making it possible to use them in stereochemical investigations of the vinyl derivatives of pyrrole. Dedicated to Boris Aleksandrovich Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 35–42, January, 2009.     

13C and19F NMR study of α,β-difluorostyryl derivatives of transition metal carbonylates. A method of signal assignment based on the carbon—fluorine spin-spin coupling constants

The¹³C and¹⁹F NMR spectra ofZ- andE-isomers of β-X-substituted α,β-difluorostyrenes (X=F, Cl, CpFe(CO)₂, Re(CO)₅, Re₂(CO)₉Na) were studied. Direct and long-range (across 1–5 bonds) spin-spin coupling constants and the (¹³C−¹²C) isotope shifts in the¹⁹F NMR spectra were determined. The study of the¹³C satellites in the¹⁹F NMR spectra of substituted difluorostyrenes permitted assignment of the¹³C NMR signals of the vinylic carbon atoms. Similarly, the signals in¹⁹F NMR spectra were assigned based on coupling constants of fluorine withipso-carbon. These assignments were found to be in good agreement with the data available from the literature (X=F, Cl). The developed approach was applied to the elucidation of the structure ofZ−PhCF=CClFe(CO)₂Cp. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya. No. 8, pp. 1575–1579, August, 1998.     

Analysis of effect of specific C-H ...X interaction on the direct13C-1H spin-spin coupling constants based onab initio quantum-chemical calculations

Anab initio quantum-chemical calculation of the direct^13C–¹H spin-spin coupling constants in the CH₄–H₂O system was carried out and experimental data obtained for a series ofN-vinyl compounds were analyzed. The specific C-H ....X (X = O, N) intramolecular interactions result in increasing the direct¹³C–¹H spin-spin coupling constant of the hydrogen involved in bonding and decreasing the direct¹³C-¹H spin-spin coupling constant for the hydrogen atom that takes no part in the interaction.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1362–1365, Tune, 1996.     

Conformation of δ-cadinol in solution

An assignment of the signals in the¹³C and¹H NMR spectra of the natural sesquiterpene alcohol δ-cadinol has been made by the NMR method (INADEQUATE, 2D-INADEQUATE, two-dimensional C-H correlation on¹J_CH constants, two-dimensional homonuclear J-spectroscopy) and the spin-spin coupling constants¹J_CC and some J_HH constants have been determined. By comparing the experimental and calculated values of the spin-spin coupling constants J_HH it has been shown that the predominant conformation of the δ-cadinol molecule in solution is that in which ring A has the half-chair form and ring B the chair form with an equatorial arrangement of the hydroxy and isopropyl groups. Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 635–638, September–October, 1990.     

Pattern recognition of the multiplet structure of NMR spectra

A new method of analysis of high-resolution NMR spectra was suggested, and an algorithm and the PAREMUS program package for assignment of patterns of the spectral components based on pattern recognition theory were developed. High effectiveness of the method has been exemplified by determination of the values and relative signs of the interring¹H−¹H and¹³C−¹H spin-spin coupling constants in 1,2,3-trichloronaphthalene. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 3, pp. 444–451, March, 1997.     

Dependence of geminal1H−1H and31P−1H spin-spin coupling constants on the specific intramolecular C−H...X interaction

Participation of the proton in a specific intramolecular C−H...X (X=N, 0) interaction leads to an increase in its geminal¹H−¹H and¹H−³¹P spin-spin coupling constants (SSCC). According toab initio calculations carried out in the 6–31G^** basis set, the observed effect is mainly due to the change in the diamagnetic spin-orbital contribution to SSCC. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 306–309, February, 1997.     

Additivity of 13C-1H and 1H-1H spin-spin coupling constants in six-membered aromatic nitrogen-containing heterocycles

We have analyzed proton-coupled ¹³C NMR and PMR spectra of pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, and 1,2,4-triazine for one-molar solutions of the compounds in DMSO-D₆. Comparison of the values obtained for the ¹³C-¹H and ¹H-¹H spin-spin coupling constants with the values calculated on the basis of the spin-spin coupling constants in pyridine and benzene has shown that it is possible to predict the constants using linear additive equations. Substantial nonlinear deviations (5–6 Hz) are observed for ¹J_CH when the carbon atom is located between two adjacent nitrogen atoms.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 986–990, July, 1985.     

Orientation of the unshared electron pair of the nitrogen atom in N-substituted 2,5-dimethyl-4-piperidinones

The axial orientation of the unshared electron pair of the nitrogen atom in cis isomers of N-substituted [R=H, CH₃, CH₂C₆H₅, or C(CH₃)₃] 2,5-dimethyl-4-piperidinones was proven by using the stereospecificity of the direct ¹³C-¹³C spin-spin coupling constants, vicinal ¹³C-¹H spin-spin coupling constants, and two-dimensional nuclear-Overhauser-effect spectroscopy (NOESY).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 512–513, April, 1989.     

Long-range13C—19F NMR spin-spin coupling in some α-trifluoromethyl-substituted polychloropyridines

High resolution¹³C NMR spectra of a series of -trifluoromethyl-substituted polychloropyridines were studied. Long-range¹³C—¹⁹F NMR spin-spin coupling through four and five bonds involving carbon atoms of the pyridine ring and the fluorine atom of the CF₃ group was found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1973–1974, October, 1995.     

Stereoselective effects in the solid-phase hydrogenation of unsaturatedl-hydroxyproline derivatives

The solid-phase catalytic hydrogenation of (R-4tert-butoxy-Δ¹-pyrroline-2-carboxylic) acid under the action of hydrogen spillover was studied. The reaction proceeds stereoselectively with the predominant formation of thel-amino acid. The configuration of the asymmetric center formed is determined by that of the asymmetric C(4) atom. The major portion of the isotope label is incorporated into the allylic C(3) and C(5) positions, and the β-H atoms are more mobile. Using quantum-chemical calculations, the geometric structure of thel-hydroxyproline molecule was calculated, and the spin-spin coupling constants for this tritium-labeled amino acid were determined. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1820–1823, October, 1997.     

Thermal, spectral and AFM studies of calcium silicate hydrate-polymer nanocomposite material

A non-ionic polymer (poly(vinyl alcohol) (PVA)) has been incorporated into the inorganic layers of calcium silicate hydrate (C–S–H) during precipitation of quasicrystalline C–S–H from aqueous solution. C–S–H and a C–S–H-polymer nanocomposite (C–S–HPN) material were synthesized and characterized by X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), ²⁹Si magic angle spinning nuclear magnetic resonance (²⁹Si MAS NMR) and ¹³C cross-polarization nuclear magnetic resonance (¹³C CP NMR) spectroscopy, atomic force microscopy (AFM), thermal conductivity, thermogravimetric analysis (TG) and differential thermal analysis (DTA). Thermal conductivity of PVA, C–S–H and C–S–HPN material was studied in the temperature range 25–50°C. C–S–HPN materials exhibited the highest thermal conductivity at 25 and 50°C. The thermal conductivity increases from 25 to 50°C are 7.03, 17.46 and 14.85% for PVA, C–S–H and C–S–HPN material, respectively. Three significant decomposition temperature ranges were observed on the TG curve of C–S–HPN material.     

Steric specificity of the direct13C-1H spin-spin coupling constants in the vinyl group in N-vinylpyrroles

Conclusions The direct¹³C-¹H spin-spin coupling constants of the vinyl group -carbon in N-vinyl-pyrroles display steric specificity and change depending on the dihedral angle between the planes of the vinyl group and the heterocycle.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1418–1421, June, 1987.     

Hammett constants and NMR shifts of α-acyloxy carboxamide derivatives

Geometrical structures, Hammett constants, ¹H and ¹³C chemical shift values, molecular electrostatic potential maps, and several thermodynamic parameters of α-acyloxy carboxamide derivatives (4a–o) were calculated using HF and DFT/B3LYP methods with 6-31G(d) basis set. The optimized structures were compared with analogous compound. The ¹H and ¹³C NMR shielding tensors were computed with the Gauge-Independent Atomic Orbital (GIAO) method. Comparison of the experimental ¹H and ¹³C NMR chemical shifts of 4a–o molecules with the theoretical data indicates good agreement.     

13C-13C spin-spin coupling constants in the spectra of monosubstituted pyridines

The ¹³C- {¹H} NMR spectra of pyridine and a number of monosubstituted pyridines for compounds with the natural percentage of the ¹³C isotope were analyzed. The direct, geminal, and vicinal ¹³C-¹³C spin-spin coupling constants (SSCC) were determined. Linear relationships that link the ¹³C-¹³C SSCC in the spectra of monosubstituted pyridines and benzenes were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1383–1385, October, 1985.     

13C-13C spin-spin coupling constants in six-membered ring azaaromatic compounds

The ¹³C-{¹H} NMR spectra of monomethyl substituted diazines, protonated at the picoline and 2-methylopyrimidine nitrogen atoms, have been analyzed, along with that of pyridine N-oxide and its 2-methyl derivatives protonated at the oxygen atom. Direct and vicinal ¹³C-¹³C spin-spin coupling constants (SSCC) have been measured. It was found that the ¹³C-¹³C SSCC in diazines follow additivity rules which are based on consideration of the number and mutual orientation or distribution of nitrogen atoms in the ring. It has also been demonstrated that increased direct ¹J_CC values involving methyl group carbon atoms in -positions to nitrogen atoms in the aromatic ring are due to effects associated with unshared electron pairs.Translated from Khimiya Geterotsiklieheskikh Soedinenii, No. 9, pp. 1243–1250, September, 1988.     

1H and 13C NMR of platinum porphyrins—II. Platinum complexes of meso-tetrakis(3,5-di-t-butyl-4-hydroxyphenyl) porphyrin and 2,3,7,8,12,13,17,18-octaethylporphyrin

The ¹H and ¹³C NMR spectra of the title compounds are reported. In both porphyrins, long-range spin-spin coupling is observed between platinum and the porphyrin protons and carbon atoms. Two-bond Pt-“α-pyrrole” carbon couplings are less than the three-bond Pt-“fβ-pyrrole” carbon and Pt-“meso-carbon” couplings. Also, large upfield shifts of the pyrrole α-carbon resonances are noted. The coupling mechanism appears to proceed via Fermi contact through the porphyrin σ-framework for the carbons, and the π-system for the protons.     

13C-13C Spin-Spin Coupling Constants in Structural Studies: XXXI. Bicyclo[2.1.0]pentane Heteroanalogs

¹³C-¹³C spin-spin coupling constants and orbital hybridization of the bridging bond in bicyclo[2.1.0]pentane heteroanalogs and their unsaturated derivatives were calculated in terms of the self-consistent finite perturbation theory (SCPT INDO). The results showed that the bridging CÄC bond in all the examined compounds has an anomaloulsy low s character.     

1H, 1 3C,and 1 5N Chemical shifts and 1H-1 5N and 1 3C-1 5N heteronuclear spin-spin coupling constants in the NMR spectra of 5-substituted furfural oximes

The ¹H, ¹³C, and ¹⁵N NMR spectra of ¹⁵N-enriched 5-substituted furfural oximes were investigated. It was shown that the chemical shifts of the ring atoms and the oxime group correlate satisfactorily with the F and R substituent constants, whereas their sensitivity to the effect of the substituents is lower than in monosubstituted furan derivatives. The constants of spin-spin coupling between the ring protons and the oxime group were determined. An analysis of the ¹H-¹H spin-spin coupling constants (SSCC) on the basis of their stereospecificity indicates that the E isomers have primarily an s-trans conformation in polar dimethyl sulfoxide, whereas the Z isomers, on the other hand, have an s-cis conformation. The signs of the direct and geminal ¹³C-¹⁵N SSCC were determined for 5-trimethylsilylfurfural oxime.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1172–1177, September, 1985.The authors thank N. O. Saldabol, L. M. Ignatovich, and N. P. Erchak for providing us with the investigated compounds.     

Study of specific C-H...N intramolecular interactions in heteroaryl vinyl ethers,on the basis of factor analysis of1H and13C NMR spectral parameters

On the basis of a factor analysis of the¹H and¹³C NMR spectral parameters of the vinyloxy group in a broad series of aryl and heteroaryl vinyl ethers, it has been established that these parameters change mainly under the influence of the electronic effect of the aromatic fragment and specific C-H...N intramolecular interaction of the -hydrogen atoms of the vinyl group with an endocyclic nitrogen atom. It has been shown that the parameters most sensitive to the specific C-H...N. interaction are the chemical shifts of the -proton and -carbon of the vinyl group, and also the spin-spin coupling constant between these atoms.Translated from Izvestiya Akademii Nauk SSSR, No. 10, pp. 2289–2297, October, 1991.