Spin-spin coupling constants of 13C-1H and 1H- 1H in 4-substituted pyridines

The spin-spin coupling constants (SSCC) of ¹³C-¹H and ¹H-¹H in 4-substituted pyridines, C₅H₄NX [X=,CN, COCH₃, COOCH₃, N(CH₃)₂, NO₂, OCH₃, Cl, Br], were investigated. To determine the constants, the proton-coupled NMR spectra of ¹³C and ¹³C-satellites in the PMR spectra of the compounds, recorded for monomolecular solutions of 4-substituted pyridines in DMSO-D₆, were analyzed. The interrelationship of the SSCC of ¹³C-¹H and ¹H-¹H in 4-substituted pyridines with the analogous constants in monosubstittued benzenes were obtained. The correlations of the constants with the F- and R-parameters of the substituents are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 948–952, July, 1984.     

13C-15N spin-spin coupling constants of amides: H-bonding effects in a cyclohexapeptide

The effect of intramolecular H-bonding and solvent acidity on the magnitude of one-bond ¹³C-¹⁵N spin-spin coupling constants has been examined using specifically ¹⁵N-labeled $\text{cyclo}$-(Gly-L-Pro-Gly)₂ and related linear peptides.     

15N13C coupling constants in 15N labelled azaadamantane

The ¹⁵N¹³C coupling constants in ¹⁵N labelled azaadamantane have been measured and interpreted in terms of their conformational dependence as compared with ¹⁵N-quinuclidine.     

Dynamic stereochemistry of erigeroside by measurement of 1H-1H and 13C-1H coupling constants

Erigeroside was extracted from Satureja khuzistanica Jamzad (Marzeh Khuzistani in Persian, family of lamiaceae), and (1)H, (13)C, (13)C{(1)H}, (1)H-(1)H COSY, HMQC and J-HMBC were obtained to identify this compound and determine a complete set of J-coupling constants ((1)J(C-H), (2)J(C-H), (3)J(C-H) and (3)J(H-H)) values within the exocyclic hydroxymethyl group (CH(2)OH) and anomeric center. In parallel, density functional theory (DFT) using B3LYP functional and split-valance 6-311++G** basis set has been used to optimized the structures and conformers of erigeroside. In all calculations solvent effects were considered using a polarized continuum (overlapping spheres) model (PCM). The dependencies of (1)J, (2)J and (3)J involving (1)H and (13)C on the C(5')-C(6') (omega), C(6')-O(6') (theta) and C(1')-O(1') (phi) torsion angles in erigeroside were computed using DFT method. Complete hyper surfaces for (1)J(C1',H1'), (2)J(C5',H6'R), (2)J(C5',H6'S), (2)J(C6',H5'), (3)J(C4',H6'R), (3)J(C4',H6'S) and (2)J(H6'R-H5'S) as well as (3)J(H5',H6'R) were obtained and used to derive Karplus equations to correlate these couplings to omega, theta and phi. These calculated J-couplings are in agreement with experimental values. These results confirm the reliability of DFT calculated coupling constants in aqueous solution.     

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.     

1H and 13C NMR study of azido-tetrazole tautomerism of 2-azido-4-methylpyrimidine

Using ¹H and ¹³C NMR and IR spectroscopic methods, it was found that 2-azido-4-methylpyrimidine exists in solutions in tautomeric equilibrium with two tetrazole forms, the ratio between which is determined by the polarity of the solvent, while in a crystalline state, according to the ¹³C NMR CP MAS data it has the structure of the 7-methyltetrazolo[1,5-a]pyrimidine isomer.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1648–1654, December, 1990.     

13C, 15N coupling constants in substituted 1,2,4-triazines-4-15N

The ¹³C,¹⁵N coupling constants in three 1,2,4-triazine-4-¹⁵N derivatives and in a substituted pyrimidine-1-¹⁵N have been determined and are compared with those in pyridine and quinoline. Of special interest are the data of the 5-(2-dimethylamino-1-propenyl)-3,6-dimethyl-1,2,4-triazine-4-¹⁵N, since one observes a characteristic alternation of the absolute value of J(¹³C,¹⁵N) along the sidechain and a hitherto unobserved very large ¹³C,¹⁵N coupling constant through four bonds of 3·9 Hz, the origin of which is attributed to the influence of the lone pair orbital on the ¹⁵N at position 4.     

13C-13C spin-spin coupling constants in 3-carene

Novosibirsk Institute of Organic Chemistry, Siberian Branch, USSR Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, Vol. 6, pp. 853–854, November–December, 1989.     

Direct13C-1H coupling constants in the vinyl group of 1-vinylpyrazoles

Conclusions The¹³C-¹H direct coupling constants in the vinyl group of 1-vinylpyrazoles are stereo-specific and vary with change in the conformer ratio.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 202–204, January, 1987.     

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.     

Configurational assignment of carbon, silicon and germanium containing propynal oximes by means of 13C-1H, 13C-13C and 15N-1H spin-spin coupling constants

Configurational assignment of five carbon, silicon and germanium containing propynal oximes has been carried out by means of experimental measurements and high-level ab initio calculations of their 13C-1H, 13C-13C and 15N-1H spin-spin coupling constants. The title compounds were shown to exist in the nonequilibrium mixture of E and Z isomers with the energy difference of less than 0.3 kcal/mol calculated at the MP2/6-311G** level.     

Use of13C-13C spin-spin coupling constants for establishing the configuration of 1-alkoxy-1-aminoxyethanes

Conclusions Direct¹³C-¹³C coupling constants were used to establish the configuration of 1-alkoxy-1-aminoxyethanes. The compounds are mixtures of Z and E isomers, of which the E isomers are more stable.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2137–2138, September, 1985.     

15N chemical shifts and long-range 1H-15N coupling pathways of selected strychnos alkaloids

The Strychnos alkaloids have been the focal point of considerable synthetic and spectroscopic effort. We now report the ¹⁵N chemical shifts and long-range ¹H-¹⁵N coupling pathways of strychnine, brucine, and holstiine at natural abundance. Long-range coupling pathways were established using a gradient-enhanced HMQC sequence optimized for the observation of ¹H-¹⁵N long-range couplings.     

Direct 13C-13C spin-spin coupling constants in the vinyl group of N-vinylazoles

The unshared electron pair of the dicoordinated nitrogen atom introduces a stereospecific contribution to the ¹³C-¹³C spin-spin coupling constant (SSCC) in the vinyl group of a series of N-vinylazoles, the value of which depends on the energetics of the unshared pair.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 197–200, February, 1989.