Trimethylene sulfite conformations: Effects of sterically demanding substituants at C-4,6 on ring geometry as assessed by 1H and 13C nuclear magnetic resonance

1978 ◽  
Vol 56 (15) ◽  
pp. 2019-2024 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Catherine M. E. Cousineau ◽  
Thomas C. Mundell
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Computer Analysis ◽  
Chemical Shifts ◽  
Tert Butyl ◽  
Nmr Data ◽  
Ring Geometry ◽  
13C Nuclear Magnetic Resonance ◽  
Sterically Demanding ◽  
C Nmr

1H and 13C nmr data for eight phenyl, diphenyl- and di-tert-butyl-2-oxo-1,3,2-dioxathianes, substituted at C-4 and/or C-6 are presented. Vicinal couplings obtained from 1H spectra by iterative computer analysis indicate chair geometries for all materials except trans-4,6-disubstituted compounds. 13C chemical shifts are corroborative.

15N and 13C nuclear magnetic resonance of deoxydinucleotide monophosphates. II. Protonation of the homo dimers deoxycytidylyl-(3′,5′)-deoxycytidine, thymidylyl-(3′,5′)-thymidine, and deoxyadenylyl-(3′,5′)-deoxyadenosine in dimethyl sulfoxide

1990 ◽  
Vol 68 (11) ◽  
pp. 2033-2038 ◽  
Author(s):  
Giovanna Barbarella ◽  
Massimo Luigi Capobianco ◽  
Luisa Tondelli ◽  
Vitaliano Tugnoli
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Dimethyl Sulfoxide ◽  
Phosphate Group ◽  
Nmr Data ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Nuclear Magnetic

The preferential protonation sites of the homo dimers deoxycytidylyl-(3′,5′)-deoxycytidine, thymidylyl-(3′,5′)-thymidine, and deoxyadenylyl-(3′,5′)-deoxyadenosine were established by nitrogen-15 and carbon-13 NMR in dimethyl sulfoxide, in the presence of varying amounts of CF3COOH. The nitrogen-15 NMR data show that in d(CpC) the capability of the two N3 nitrogens to accept the proton is slightly different. In d(TpT) and d(ApA) the protonation of the phosphate group leads to significant variations of the chemical shift of the carbons adjacent to phosphorus. Keywords: deoxydinucleotides, protonation, 15N and 13C NMR.

13C nuclear magnetic resonance and Raman investigations of aqueous carbon dioxide systems

1982 ◽  
Vol 60 (8) ◽  
pp. 1000-1006 ◽  
Author(s):  
Theresa M. Abbott ◽  
Gerald W. Buchanan ◽  
Peeter Kruus ◽  
Keith C. Lee
Keyword(s):  
Carbon Dioxide ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Linear Relationship ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Carbonate Ion ◽  
13C Nuclear Magnetic Resonance ◽  
Wide Range ◽  
C Nmr

13C-nmr spectra of carbon dioxide in water are reported for a wide range in pH. Chemical shifts were determined for the following species: CO2(g), CO2(aq), HCO3−(aq), CO32−(aq). A linear relationship was found between the shift of the 13C line and the fraction of carbonate ion calculated to be present, as well as between the ratio of the area under the 1067 cm−1 (carbonate) Raman peak to the sum of the area under the 1067 cm−1 and 1017 cm−1 (bicarbonate) peaks and the fraction carbonate.

Solvent and α-substituent perturbations of the 2H/1H isotope shifts in the 13C nuclear magnetic resonance of toluene-α-d3

1987 ◽  
Vol 65 (3) ◽  
pp. 534-537 ◽  
Author(s):  
Ted Schaefer ◽  
James Peeling ◽  
Rudy Sebastian
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Refractive Index ◽  
Magnetic Resonance ◽  
Isotope Effect ◽  
Electron Donor ◽  
Chemical Shifts ◽  
Aromatic System ◽  
Expectation Value ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

The 2H/1H isotope effect on 13C nmr chemical shifts, nΔ, n being the number of intervening bonds between 2H and 13C nuclei, in toluene-α-d3 is solvent dependent. For example, 1Δ ranges from 817 ppb in CD3OH to 869 ppb in acetone-d6 solutions, a positive number indicating increased shielding in the deuterated species. 1Δ is linearly dependent on a function of the refractive index, nD, of the solvent, allowing extrapolation to nD = 1. The hyperconjugative model, in which the C—D bond is a poorer electron donor to the aromatic system than is a C—H bond, is tested for the substituents CH2D, CHD2, CD3, CHDCH3, CD2CH3, CD(CH3)2, C6H5CHD, and (C6H5)2CD. For these substituents, the negative 5Δ is linearly related to the expectation value of sin2 θ; θ is the angle by which the C—D bond twists out of the benzene plane. The model fails quantitatively for C6H5CD2X (X = Cl, COOH, CN, OH). For X = OH, very large negative 5Δ and 3Δ values are observed. nΔ is also reported for 4-ethyltoluene-α-d3 and benzaldehyde-α-d1. For the latter, all nΔ values are positive other than 5Δ, which vanishes in acetone-d6 solution.

Medium-sized cyclophanes. XX. 13C nuclear magnetic resonance of cyclophanes: p-orbital compression shift and orbital deformation

1976 ◽  
Vol 54 (21) ◽  
pp. 3412-3418 ◽  
Author(s):  
Tetsuo Takemura ◽  
Takeo Sato
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Methylene Carbon ◽  
Upfield Shift ◽  
13C Nuclear Magnetic Resonance ◽  
Orbital Axis ◽  
C Nmr

The 13C nmr spectra of [2.2]meta-, metapara-, and paracyclophanes were determined. By comparing the chemical shifts with those of acyclic models two types of anomalies were revealed.(1) Bridging methylene carbon resonances for [2.2]metacyclophanes having an alkyl group ortho to the bridge were shifted upfield as a result of van der Waals' compression. The upfield shift is much larger (5–12 ppm) for cyclophanes than for models (2–4 ppm) reflecting the rigid nature of the molecular geometry of the former.(2) Interestingly, inner aryl carbon resonances in [2.2]metacyclophanes and protonated aryl carbon resonances in [2.2]paracyclophanes were shifted downfield by 6–7 ppm. The complementary upfield shift of uncompressed atoms, hydrogen or carbon, connected to those carbons was also noticed. The downfield shift of compressed sp2 carbon results from interaction between two p-orbitals along the same orbital axis, p-orbital compression, and is attributable to decreased electron density.

A stereochemical investigation of substituted ethylene sulfites via 13C nuclear magnetic resonance

1976 ◽  
Vol 54 (9) ◽  
pp. 1428-1432 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Desmond G. Hellier
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformational Analysis ◽  
Sulfur Atom ◽  
Chemical Shifts ◽  
Nmr Chemical Shifts ◽  
13C Nuclear Magnetic Resonance ◽  
Ethylene Sulfite ◽  
C Nmr ◽  
Nuclear Magnetic

13C nmr chemical shifts for ethylene sulfite and 17 derivatives are presented. From the magnitudes of the γ shifts and the tenets of conformational analysis, support is gained for the existence of twist-envelope conformations in solution. Pseudorotational paths are suggested which do not involve inversion at the sulfur atom.

13C nuclear magnetic resonance spectral and conformational analysis of naturally occurring tetrahydrofuran lignans

1979 ◽  
Vol 57 (4) ◽  
pp. 441-443 ◽  
Author(s):  
Sebastião F. Fonseca ◽  
Lauro E. S. Barata ◽  
Edmundo A. Rúveda ◽  
Paul M. Baker
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformational Analysis ◽  
Nmr Spectra ◽  
H Nmr ◽  
Naturally Occurring ◽  
Nmr Data ◽  
Benzylic Carbon ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

The 13C nmr spectra of the naturally occurring stereoisomers of the tetrahydrofuran lignans were recorded and the signals assigned. Based on these assignments, on the observed sensitivity of the benzylic carbon shifts to the orientation of the aryl groups, and on the comparison with previously reported 1H nmr data, the most probable conformations for the mentioned stereoisomers are suggested.

29Si-, 31P- und 13C-Kernresonanzuntersuchungen an N-silylierten Triorganophosphiniminen / Silicon-29, Phosphorus-31, and Carbon-13 Nuclear Magnetic Resonance Investigations of N-Silylated Triorganophosphine Imines

1977 ◽  
Vol 32 (9) ◽  
pp. 967-974 ◽  
Author(s):  
Wolfgang Buchner ◽  
Werner Wolfsberger
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Spin Splitting ◽  
Bonding Mechanism ◽  
Nmr Data ◽  
Qualitative Interpretation ◽  
Chloro Derivatives ◽  
C Nmr ◽  
Nuclear Magnetic

29Si, 31P and, in part, 13C NMR data are reported for N-trimethylsilyl-triorganophosphine imines as well as some siliconsubstituted methoxy and chloro derivatives. The spin-spin splitting pattern of the 29Si{1H} spectra is discussed for disilanes of the type (RR′R″P=N-SiMe2-)2. A qualitative interpretation of 29Si chemical shifts is preferably being based on hyperconjugation rather than a (p-d)n bonding mechanism. The preparation of a series of bis(phosphinimino)silanes and 1,2-bis(phosphinimino)disilanes is described.

Nuphar thiaspirane sulfoxides. 13C nuclear magnetic resonance determined configuration and utilization in the interconversion of thiaspirane stereochemical types

1978 ◽  
Vol 56 (1) ◽  
pp. 56-61 ◽  
Author(s):  
R. T. LaLonde ◽  
C. F. Wong
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Subsequent Reduction ◽  
13C Nuclear Magnetic Resonance ◽  
Sodium Borodeuteride ◽  
C Nmr ◽  
Nuclear Magnetic

The configuration of the sulfoxide oxygen in syn- and anti-thiobinupharidine sulfoxide was determined by employing the 13C nmr sulfoxidation increments of C-6. Establishment of the 13C nmr line assignments for C-6 included the study of the C-6 and C-6′ deuterated thiobinupharidine and the corresponding sulfoxides. Thermolysis of syn-thiobinupharidine sulfoxide in DMSO and subsequent reduction with sodium borodeuteride in methanol yielded thiobinupharidine, labelled with deuterium only at C-6, and thionuphlutine B, labelled with deuterium at both C-6 and C-6′. Treatment of the anti sulfoxide in xylene or DMSO resulted in no thiobinupharidine or thionuphlutine B. Similarly, syn-neothiobinupharidine sulfoxide gave neothiobinupharidine and a new thiaspirane, thionuphlutine C. These two compounds were not produced from anti-neothiobinupharidine sulfoxide heated in xylene.

Semiempirical calculation of 13C nuclear magnetic resonance chemical shifts of acyclic hydrocarbons. Application to the stereochemical analysis of steroidal side chains

1988 ◽  
Vol 66 (1) ◽  
pp. 71-75 ◽  
Author(s):  
Manuel Gonzalez-Sierra ◽  
Daniel A. Bustos ◽  
Edmundo A. Ruveda ◽  
Alejandro C. Olivieri ◽  
Mariano Grasselli
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Side Chains ◽  
Stereochemical Analysis ◽  
Microcomputer Program ◽  
Semiempirical Approach ◽  
13C Nuclear Magnetic Resonance ◽  
Acyclic Hydrocarbons ◽  
Nuclear Magnetic

A semiempirical approach for predicting 13C nuclear magnetic resonance chemical shifts of acyclic hydrocarbons has been adapted to a microcomputer program. A series of methyl and dimethyl substituted cholesterols has been studied using this program, and the predicted shifts are in agreement with literature reports. Preferred conformations of the steroidal side chains have been also predicted and agree with previous studies. A simple rule for analyzing the trends in the chemical shift of the carbon C-20, which is sensitive to changes in the configuration at C-22, is also given, not only for hydrocarbon side chains but also for hydroxy substituted compounds.

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