Search results for "Carbon-13 NMR satellite"

NMR Spectroscopic and quantum chemical characterization of the (E)- and (Z)- isomers of the penta-1,3-dienyl-2-cation

2003

Dilute solutions of the (E )− and (Z )− isomers of pent-1,3-dienyl-2-cations (1) were obtained from reaction of 4-chloro-1,2-pentadiene (2) with SbF5 in SO2ClF/SO2F2 at −135 °C using high-vacuum co-condensation techniques. The experimental NMR spectra of the mixture of the two isomers were compared with quantum chemical 13C NMR chemical shift calculations at HF-SCF, MP2, CCSD and CCSD(T) levels using MP2/tzp geometries. Quantum chemical shift calculations were performed with a tzp basis (9s5p1d/5s3p1d) for carbon and a dz basis (4s/2s) for hydrogen using gauge-including atomic orbitals (GIAOs). The HF-SCF calculations deviate significantly for the positively charged carbon atoms of the ally…

NMR crystallography of 2-Acylamino-6-[1H]pyridones: solid state NMR, GIPAW computational, and single crystal X-ray diffraction studies

2011

Abstract 2-Acylamino-6-[1H]-pyridones [acyl = RCO, where R = methyl (1), ethyl (2), iso-propyl (3), tert-butyl (4), and 1-adamantyl (5)] have been synthesized and characterized by NMR spectroscopy. From three congeners, 2, 3 and 5, also single crystal X-ray structures have been solved. For these derivatives GIPAW calculations acts as a “bridge” between solid-state NMR data and calculated chemical shifts based on X-ray determined geometry. In crystals all three compounds exist as pyridone tautomers possessing similar six-membered ring structure stabilized by intramolecular C O⋯HN hydrogen bond. Theoretical GIPAW calculated and experimental 13C and 15N CPMAS NMR shifts are in excellent agreem…

13C and15N NMR study of substituted 1,2,4-triazines

1995

13C and 15N NMR spectra of eight substituted 1,2,4-triazines were measured and assigned. The assignments of the 13C NMR spectra were based on the substituent chemical shifts and nJ(C,H) coupling constants. 15N NMR chemical shifts generally showing well separated ranges were assigned by the proton coupled 15N NMR spectra. 15N NMR chemical shifts of N-4 in 3- and 5-methoxy or -thiomethyl-substituted 1,2,4-triazines were found to be related significantly (confidence level >99%) with the π-charge at N-4 calculated by a semi-empirical molecular orbital (AM1) procedure. For the 15N NMR chemical shifts of N-1 and N-2, no reliable correlations with the molecular electronic properties such as AM1 π-…

Complete Spectral Analysis of the1H NMR 16-Spin System of β-Pinene

1997

The complete analysis of the 1H NMR spectrum of β-pinene, (1S)-(-)-6,6-dimethyl-2-methylenebicyclo[3.1.1]heptane, which is of the ABCDEFGHIJX3Y3 type, is reported and earlier results are corrected. The vicinal coupling constants, 3J(H,H), are compared with the theoretical values calculated by using the Altona and co-workers’ equations for the structure derived by molecular modelling. The results were applied to the conformational analysis of β-pinene. © 1997 John Wiley & Sons, Ltd.

?-Phenylsulfonyl-N-arylacetamides (?-phenylsulfonylacetanilides):1H,13C and15N NMR spectral characterization

2000

Multinuclear magnetic resonance and x-ray diffraction studies of aminonitropyridines

1992

The 15N NMR spectra for 21 aminonitropyridines were measured and their chemical shifts assigned. The 1H and 13C NMR chemical shifts and spin–spin coupling constants were also determined for 16 compounds of this series. In order to relate the structural properties of nitramino groups and their 15N NMR chemical shifts in 2- and 4-nitramino-3-nitropyridines, which differ remarkably from all other amino groups studied, low-temperature 1H NMR, 17O NMR, comparative INEPT and IR spectroscopic studies were carried out. In addition, the x-ray crystal structure of 2-nitramino-3-nitropyridine was determined. Comparative spectroscopic studies showed that the nitramino derivatives exhibit different char…

NMR spectral and X-ray structural investigation of 1,3-bis(2-quinolyl)-2-(p-chlorophenyl)-2-propanol

2000

Abstract 1,3-Bis(2-quinolyl)-2-(p-chlorophenyl)-2-propanol (BQCP) has been prepared and characterised by 1H, 13C, 15N NMR spectral and X-ray structural parameters. The methylene protons of BQCP are diastereotopic in solution (CDCl3) as revealed by 1H NMR. In crystalline state there exists an intramolecular hydrogen bond O–H⋯N with one of two nitrogen atoms in BQCP. Variable temperature 1H NMR and PFG 1H, 15N HMBC runs show that in solution BQCP shows C2v-symmetry (both CH2-2-quinolyl fragments are equivalent) in NMR-time scale due to a fast exchange of the hydrogen bond from one nitrogen to the other even at 223 K.

1H, 13C and 17O NMR spectral study of chlorinated 3,4-dihydroxybenzaldehydes (protocatechualdehydes)

1995

Abstract Chlorinated 3,4-dihydroxybenzaldehydes have been studied by means of 1 H, 13 C and 17 O NMR spectroscopy. The 1 H and 13 C NMR spectral assignments are based on 2-dimensional 13 C- 1 H chemical shift correlation spectroscopy (COSY). The 17 O NMR measurements at natural isotope content in organic solvents are problematic owing to the poor solubility of the compounds and/or broadness of the resonance lines. In aqueous alkaline solutions, however, all protocatechualdehydes exhibit “easy-to-detect” 17 O NMR spectral characteristics. The 17 O NMR chemical shifts in the range of 140–480 p.p.m. are interpreted as arising from the different canonical structures of formyl substituted phenol…

13C NMR spectroscopy of four tertiary methyl norbornenols and norbornanols

1975

Carbon chemical shifts and direct 13C1H coupling constants of 2-endo-methyl-5-norbornen-2-exo-ol, 2-exo-methyl-5-norbornen-2-endo-ol, 2-endo-methylnorbornan-2-exo-ol and 2-exo-methylnorbornan-2-endo-ol have been measured from single samples using a dual probe pulse Fourier transform method.

Predominance of inductive over resonance substituent effect on33S NMR chemical shifts of 4-substituted phenyl-4′-methylphenacyl sulfones

1999

33S NMR chemical shifts have been determined for the first time for a series of 10 substituted phenacyl sulfones. Electron-withdrawing and electron-releasing substituents in 4-substituted phenyl-4′-methylphenacyl sulfones, p-MeC6H4COCH2SO2C6H4R-p, cause a ‘reverse’ substituent effect on the 33S NMR resonance. Dual-substituent parameter (DSP) analysis of δ(33S) values revealed that the inductive effect of the substituent predominates over its resonance effect. This finding shows that the 33S NMR chemical shifts are of importance in estimating the electronic properties of sulfur-containing compounds. The 13C and 17O NMR chemical shifts of the title compounds are also discussed. Copyright © 19…