Carbon-13 Nuclear Magnetic Resonance Spectra of Isothiazole, 1,2-Dithiole, and 1,3-Dithiole Derivatives

1975 ◽  
Vol 53 (6) ◽  
pp. 836-844 ◽  
Author(s):  
N. Plavac ◽  
I. W. J. Still ◽  
M. S. Chauhan ◽  
D. M. McKinnon
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Carbonyl Compounds ◽  
Heterocyclic Compounds ◽  
Chemical Shifts ◽  
Conjugated Systems ◽  
Nuclear Magnetic Resonance Spectra ◽  
Chemical Shift Data ◽  
Shift Data

Carbon-13 chemical shift data have been obtained for a number of isothiazole, benzo[c]isothiazole, 1,2-dithiole, and 1,3-dithiole derivatives. A number of these compounds are thiones and the chemical shifts of the C=S carbons are discussed in the light of recent attempts to predict such chemical shifts from those of the analogous carbonyl compounds. Comparisons of substituent chemical shift (s.c.s.) effects in these heterocyclic compounds with those in simpler aromatic or conjugated systems have been made and additivity correlations tested in a number of cases.

Nuclear magnetic resonance spectra, stereochemistry, and conformation of flavan derivatives

1964 ◽  
Vol 17 (6) ◽  
pp. 632 ◽  
Author(s):  
JW Clark-Lewis ◽  
LM Jackman ◽  
TM Spotswood
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Heterocyclic Ring ◽  
Coupling Constant ◽  
Nuclear Magnetic Resonance Spectra ◽  
Chemical Shift Data ◽  
Shift Data ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Chemical-shift and coupling-constant data for protons in 68 flavan derivatives are reported. Coupling-constant data for interactions involving the 2-, 3-, and 4-protons have been used to define the configuration of the 2-, 3-, and 4-substituents and the conformation of the heterocyclic ring. It is shown that chemical-shift data for protons of the heterocyclic ring and of 3- and 4-acetoxyl groups are of little value in stereochemical studies. Analysis of the absorptions of the aromatic protons shows that N.M.R. is useful for determining the oxygenation pattern in rings A and B.

17O nuclear magnetic resonance spectroscopic study of substituted phthalic anhydrides and phthalides

1987 ◽  
Vol 65 (6) ◽  
pp. 1214-1217 ◽  
Author(s):  
David W. Boykin ◽  
Alfons L. Baumstark ◽  
Margaret M. Kayser ◽  
Chantal M. Soucy
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Carbonyl Groups ◽  
Chemical Shift Data ◽  
The Relationship ◽  
Electronic Character ◽  
Shift Data ◽  
Phthalic Anhydrides

17O chemical shift data (natural abundance) for 3-substituted phthalic anhydrides and 4- and 7-substituted phthalides in acetonitrile at 75 °C are reported. Steric interactions of substituents ortho to the carbonyl groups result in deshielding effects (9–22 ppm) relative to parent compounds regardless of the electronic character of the substituents. Factors contributing to the deshielding effects are discussed. The relationship between 17O chemical shifts and regiochemistry of the phthalic anhydrides is discussed.

Organometallic compounds in synthesis. VIII. Carbon-13 nuclear magnetic resonance spectroscopic study of tricarbonylcyclohexadienyliron salts

1976 ◽  
Vol 29 (8) ◽  
pp. 1671 ◽  
Author(s):  
AJ Birch ◽  
PW Westerman ◽  
AJ Pearson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Spectroscopic Study ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Organometallic Compounds ◽  
Nucleophilic Attack ◽  
Chemical Shift Data ◽  
Shift Data

The carbon-13 N.M.R. spectra of eleven substituted tricarbonylcyclohexadienyliron salts (1) have been determined and individual resonances assigned. Substituent effects have been deduced and compared with corresponding effects in cyclohexadienyl cations. The structures of the tricarbonylcyclohexadienyliron salts are discussed with reference to chemical shift data. The proportions of irreversible nucleophilic attack at the terminal positions in the unsymmetrical 2-substituted salts are compared with the observed chemical shifts at these carbon atoms.

Metabolites of bird's nest fungi. Part 10. Carbon-13 nuclear magnetic resonance studies on the cyathins

1978 ◽  
Vol 56 (16) ◽  
pp. 2197-2199 ◽  
Author(s):  
William A. Ayer ◽  
Thomas T. Nakashima ◽  
Dale E. Ward
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Chemical Shift Data ◽  
Related Compounds ◽  
Shift Data ◽  
Methyl Acetal ◽  
Magnetic Resonance Spectra

The carbon-13 magnetic resonance spectra of cyathin A3 and several related compounds have been measured and the chemical shifts have been assigned. The chemical shift data have been used to determine the stereochemistry at C-1 in cyafrin A4 and to determine the position of the bromine in 1-bromoallocyathin A3 methyl acetal.

Selenium-77 nuclear magnetic resonance studies of selenols, diselenides, and selenenyl sulfides

1988 ◽  
Vol 66 (1) ◽  
pp. 54-60 ◽  
Author(s):  
Khoon-Sin Tan ◽  
Alan P. Arnold ◽  
Dallas L. Rabenstein
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Proton Exchange ◽  
Exchange Reactions ◽  
Nuclear Magnetic Resonance Spectra ◽  
Ph Range ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

77Se and 1H nuclear magnetic resonance spectra have been measured for selenols (RSeH), diselenides (RSeSeR), and selenenyl sulfides (RSeSR′), including selenenyl sulfides formed by reaction of glutathione and penicillamine with selenocystine and related diselenides. Exchange processes strongly affect the 77Se and 1H nuclear magnetic resonance spectra of all three classes of compounds. Sharp, exchange-averaged resonances are observed in the 1H nuclear magnetic resonance spectra of selenols; however, selenol proton exchange causes the 77Se resonances to be extremely broad over the pH range where the selenol group is titrated. Selenol/diselenide exchange [Formula: see text] also results in exchange-averaged 1H resonances for solutions containing RSeH and RSeSeR; however, the 77Se resonances were too broad to detect. Exchange reactions have similar effects on nuclear magnetic resonance spectra of solutions containing selenols and selenenyl sulfides. The results indicate selenol/diselenide exchange is much faster than thiol/disulfide exchange. The 77Se chemical shift depends on the chemical state of the selenium, e.g., titration of the selenol group of selenocysteamine causes the 77Se resonance to be shielded by 164 ppm, oxidation of the selenol to form the diselenide selenocystamine causes a deshielding of 333 ppm, and oxidation to form the selenenyl sulfide [Formula: see text] results in a deshielding of 404 ppm. 77Se chemical shifts were found to be in the range −240 to −270 ppm (relative to (CH3)2Se) for selenolates, approximately −80 ppm for selenols, 230–360 ppm for diselenides, and 250–340 ppm for selenenyl sulfides. The 77Se chemical shift is also affected by titration of neighboring carboxylic acid and ammonium groups, and their pkA values can be calculated from 77Se chemical shift data.

Nuclear magnetic resonance spectra of pyrrolizidine alkaloids. II. The pyrrolizidine nucleus in ester and non-ester alkaloids and their derivatives

1965 ◽  
Vol 18 (10) ◽  
pp. 1625 ◽  
Author(s):  
CCJ Culvenor ◽  
WG Woods
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Pyrrolizidine Alkaloids ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Vicinal Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
Saturated Ring ◽  
Magnetic Resonance Spectra

Chemical shifts and coupling constants are tabulated for the protons of the pyrrolizidine nucleus in 40 pyrrolizidine alkaloids and derivatives. The effect of acylation of hydroxyl substituents on C7 and C9 and the very large difference in chemical shift of the H9 protons in the macrocyclic diester alkaloids is discussed. The direction of buckling of the saturated ring can be ascertained from the H5,H6 vicinal coupling constants or from the width of the H7 multiplet if H7 bears an oxygen substituent. In general, retronecine derivatives are exo-buckled whereas heliotridine derivatives consist of interconverting exo- and endo-buckled forms.

Determination of for aliphatic ketones from nuclear magnetic resonance chemical shift data

1970 ◽  
Vol 48 (12) ◽  
pp. 1919-1923 ◽  
Author(s):  
Donald G. Lee
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Raman Spectroscopy ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Aliphatic Ketones ◽  
Chemical Shift Data ◽  
Shift Data ◽  
Good Agreement ◽  
Nuclear Magnetic

The [Formula: see text] values for 3-pentanone, 2-butanone, and 3-methyl-2-butanone have been determined from chemical shift data. The values (−7.6, −7.1, and −7.2, respectively) are in good agreement with those previously determined for aliphatic ketones by use of ultraviolet–visible and Raman spectroscopy.

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.

NUCLEAR MAGNETIC RESONANCE SPECTRA AND CONDUCTIVITIES OF SOME METAL ACETYLACETONATES

1965 ◽  
Vol 43 (9) ◽  
pp. 2559-2565 ◽  
Author(s):  
A. J. Carty ◽  
D. G. Tuck ◽  
E. Bullock
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spectroscopic Studies ◽  
Metal Acetylacetonates ◽  
Group Iii ◽  
Nuclear Magnetic Resonance Spectra ◽  
Chemical Shift Data ◽  
Shift Data ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Chemical shift data and conductivities of acetylacetonates of some group IA, IIA, and IIIA metals in dimethylsulfoxide are recorded. It is concluded that nuclear magnetic resonance spectra cannot give definite information on π-bonding in these complexes, though the results for the group III elements are consistent with the presence of such bonds, as is the evidence from related spectroscopic studies.

Proportionality relationships in the carbon-13 nuclear magnetic resonance spectra of para-disubstituted benzenes: a new interpretation of non-additive behavior

1977 ◽  
Vol 55 (3) ◽  
pp. 541-547 ◽  
Author(s):  
Brian Maurice Lynch
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Excitation Energy ◽  
Chemical Shifts ◽  
Correlation Coefficients ◽  
Energy Term ◽  
Nuclear Magnetic Resonance Spectra ◽  
New Interpretation ◽  
Parameter Approach

The carbon-13 chemical shifts for 214 distinct sites (the 4-carbons) in 24 sets of 1-X,4-Y-disubstituted benzenes and for 270 distinct sites (the 1- and 2-carbons) in 16 of these sets are reproduced with excellent precision (correlation coefficients 0.99 or greater) either by linear proportionality relationships with the appropriate substituent chemical shift (scs) in a mono-substituted benzene (for the 4-carbons), or by simple additivity relationships with the scs (for the 1- and 2-carbons).Inconsistencies are pointed out in a theoretical rationalization of 4-carbon shifts used in discussing the non-additivity of these shifts in terms of a DSP approach, whereas the above one-parameter approach yields sets of proportionality constants (slopes of scs relative to Y = H) following systematic trends which are interpreted as results of changes in the excitation energy term at carbon-4 dependent upon the ionization potential of the group Y. There is no significant association between the scs slopes and sets of calculated CNDO/2 electron densities for these para-disubstituted benzenes.

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