13C Fourier Transform Nuclear Magnetic Resonance. XI. Pyridine N-Oxide Derivatives

1975 ◽  
Vol 53 (22) ◽  
pp. 3419-3424 ◽  
Author(s):  
Robert J. Cushley ◽  
David Naugler ◽  
Carlos Ortiz
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
Magnetic Resonance ◽  
Electric Field ◽  
Chemical Shifts ◽  
Molecular Orbital Calculations ◽  
Excess Charge ◽  
Pyridine Derivatives ◽  
Upfield Shift ◽  
Electric Field Mechanism

Formation of the N-oxide for several pyridine derivatives results in a large upfield shift of the 2-, 4-, and 6-carbons and a significant downfield shift of the 3- and 5-carbons. The chemical shifts (Δδ) are consistent with a resonance and electric field mechanism. Molecular orbital calculations using CNDO/2 show a qualitative correlation between excess charge density and Δδ.

15N Nuclear Magnetic-Resonance Spectra of ortho-Substituted Phenylacetanilides: The Origin of γ-syn Effects

1989 ◽  
Vol 42 (4) ◽  
pp. 463 ◽  
Author(s):  
C Yamagami ◽  
N Takao ◽  
Y Takeuchi
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Aromatic Ring ◽  
Chemical Shifts ◽  
Van Der Waals ◽  
Side Chains ◽  
Upfield Shift ◽  
Nuclear Magnetic Resonance Spectra ◽  
The Difference ◽  
Magnetic Resonance Spectra

The 15N chemical shifts of X α and Y α, i.e., the nuclei through which the side chains, X and Y, respectively, of o-substituted phenylacetanilides (2a) are bonded to the aromatic ring were determined. There was observed a uniform upfield shift (γsyn effect). In order to explore the origin of the γ effect, other o-disubstitutes benzenes (2b-d) were also examined. The values of D, defined as the difference between γ α substituent chemical shifts of the ortho (2) and para (3) series of compounds, and considered as a measure of the γ-syn effect, were correlated with various electronic and steric substituent parameters. Correlations with electronegativity and van der Waals terms were successful. Examination of the correlations indicated that the γ-syn effect is mostly governed by electronegativity. The classic steric compression theory does not seem very convincing as a means of explaining the shielding γ-syn effect observed in the present study.

Carbon-13 Fourier Transform Nuclear Magnetic Resonance. IX. Complete Assignments of Some Prodigiosins. Bioincorporation of Label

1975 ◽  
Vol 53 (1) ◽  
pp. 148-160 ◽  
Author(s):  
Robert J. Cushley ◽  
Richard J. Sykes ◽  
C.-K. Shaw ◽  
Harry H. Wasserman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Effective Means ◽  
Substituted Pyrroles ◽  
Biosynthetic Studies ◽  
Complete Interpretation ◽  
Comprehensive Study ◽  
Nuclear Magnetic

A comprehensive study has been made of the carbon-13 chemical shifts of substituted pyrroles. The data, together with perdeuteration, single resonance, and off-resonance techniques, formed the basis for the complete interpretation of the carbon-13 spectra of the prodigiosins. Based on these assignments the biosynthetic origin of the prodigiosin carbons was elucidated, with further biosynthetic studies to be reported.Carbon-13 chemical shifts are shown to be an effective means of determining sites of protonation.

NOTIZEN: Use of 95Mo NMR for Identification of Molybdenum (VI) Chalcogenide Anions in Aqueous Solution

1977 ◽  
Vol 32 (5) ◽  
pp. 505-506 ◽  
Author(s):  
O. Lutz ◽  
A. Nolle ◽  
P. Kroneck
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
Magnetic Resonance ◽  
Aqueous Solutions ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Nuclear Magnetic

Abstract95Mo Fourier transform nuclear magnetic resonance studies were made on aqueous solutions of oxo thiomolybdates. Chemical shifts up to 2200 ppm were found for the different unambiguously assigned species MoO4-nSn2- (n = 0, 1, 2, 3, 4).

13C nuclear magnetic resonance spectra of 3,6-disubstituted pyridazines

1991 ◽  
Vol 69 (6) ◽  
pp. 972-977 ◽  
Author(s):  
Gottfried Heinisch ◽  
Wolfgang Holzer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13C nuclear magnetic resonance spectra of 17 3,6-disubstituted pyridazine derivatives have been systematically analyzed. Chemical shifts and various 13C, 1H coupling constants are reported. Attempts were made to correlate these data with results obtained from semiempirical molecular orbital calculations as well as with substituent electronegativities and Taft's substituent constants σI and σR0. Key words: 3,6-disubstituted pyridazines, 13C NMR spectroscopy, 13C, 1H spin coupling constants.

Nuclear Magnetic Resonance of Compounds Related to DDT: Part II. Aromatic Protons

1968 ◽  
Vol 22 (5) ◽  
pp. 506-512 ◽  
Author(s):  
Norman E. Sharpless ◽  
Robert B. Bradley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Electron Density ◽  
Chemical Shifts ◽  
Molecular Orbital Calculations ◽  
Aromatic Rings ◽  
Butyl Group ◽  
Nuclear Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The nuclear magnetic resonance spectra of the aromatic protons of DDT and 31 of its analogs and derivatives have been analyzed. Chemical shifts of these molecules are functions of the electronegativities of the substituents on the ring, as well as those in the aliphatic portion, although substitution of the ring chlorine in DDT by either a nitro or a t-butyl group leads to anomalous values. Molecular orbital calculations show that the chemical shift of the proton ortho to the ring substituent depends upon the π electron density at the corresponding carbon, but the chemical shift of the proton meta to this substituent is independent of the π electron density at the corresponding carbon. The data also indicate that the two aromatic rings in DDT are independent of each other.

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.

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