The 19F Nuclear Magnetic Resonance Spectra of Octahedral Fluorothiocyanato-N- and Fluorocyanato-N-Titanates(IV)

1974 ◽  
Vol 52 (4) ◽  
pp. 667-673 ◽  
Author(s):  
Philip A. W. Dean ◽  
Brian J. Ferguson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
Stable Equilibrium ◽  
Chemical Shifts ◽  
Mixed Species ◽  
Nuclear Magnetic Resonance Spectra ◽  
Donor Ability ◽  
The Individual ◽  
Cis And Trans ◽  
Back Donation

The low temperature 19F n.m.r. spectra of the mixtures TiF62−−TiX62− (X = Cl−, Br−, NCS−, NCO−) in sulfur dioxide solution have been examined. When X = Cl− or Br− rapid fluorine exchange is occurring even at the lowest accessible temperature, but when X = NCS− or NCO− the spectra of the individual mixed species TiF6−xXx2− are observed. In the latter two cases the solutions also contain fluorine-bridged dimers in stable equilibrium. The 19F chemical shifts of TiF6−xXx2− (X = NCS− or NCO−) and of some related mixed complexes are reasonably represented by the equation δ = pC + qT where C and T are constants characteristic of the substituent X and p and q are the number of ligands X cis and trans respectively to the resonating fluorine. The constants T appear to be a measure of the π-donor ability of the ligand X in these complexes, supporting the idea that the chemical shift of a fluorine in fluorotitanates is determined largely by the extent to which fluorine-to-titanium back donation occurs.

Carbon-13 nuclear magnetic resonance spectra of N-, O-, and S-methylated uracil and thiouracil derivatives

1978 ◽  
Vol 56 (5) ◽  
pp. 725-729 ◽  
Author(s):  
Ian W. J. Still ◽  
Nick Plavac ◽  
David M. McKinnon ◽  
Mohinder S. Chauhan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
General Type ◽  
Chemical Shifts ◽  
Pyrimidine Derivatives ◽  
Aromatic Substituent ◽  
Nuclear Magnetic Resonance Spectra ◽  
Derivatives Of ◽  
Thiouracil Derivatives ◽  
C Nmr

13C nmr chemical shifts have been recorded for a number of uracil, thiouracil, and pyrimidine derivatives. These data are discussed in relation to what is known of the lactam–lactim tautomerism in such systems and possible correlations of chemical shifts with normal aromatic substituent chemical shift parameters. The chemical shifts for the CH3 groups in simple methylated derivatives of uracil are very characteristic of the site of methylation and should prove useful as a tool for assigning structures to alkylated derivatives of this general type.

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.

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.

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.

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.

13C nuclear magnetic resonance spectra of steroids: the assignments of chemical shifts for C-15 and C-16 in 17β-acetyl steroids

1976 ◽  
Vol 54 (23) ◽  
pp. 3766-3768 ◽  
Author(s):  
Dong Je Kim ◽  
Lawrence D. Colebrook ◽  
T. J. Adley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Chemical Shift Assignments ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Previously reported 13C chemical shift assignments for C-15 and C-16 of a number of 17β-acetyl steroids related to progesterone have been shown to be reversed. Based on the revised assignment the effect of bromo- and hydroxy-substitution at C-17 on C-12, C-14, C-15, and C-16 is assessed.

Nuclear magnetic resonance spectra of pyrrolizidine alkaloids. I. The spectra of retronecine and heliotridine

1965 ◽  
Vol 18 (10) ◽  
pp. 1605 ◽  
Author(s):  
CCJ Culvenor ◽  
ML Heffernen ◽  
WG Woods
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Detailed Analysis ◽  
Pyrrolizidine Alkaloids ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The chemical shifts and coupling constants of the protons in retronecine and heliotridine are derived by detailed analysis of the nuclear magnetic resonance spectra of these compounds. The factors which influence the appearance and ease of interpretation of spectra of pyrrolizidine derivatives, principally the chemical shift difference of the H 6 protons and conformational averaging, are discussed. The conformations of retronecine and heliotridine are discussed in relation to their coupling constants; the former compound is exo-buckled whereas the latter is a mixture of rapidly interconverting exo- and endo-buckled forms.

Carbon-13 nuclear magnetic resonance spectra of organic sulfur compounds. Comparison of chemical shifts for carbonyl and thiocarbonyl compounds in the pyrone, thiopyrone, and pyridone series

1976 ◽  
Vol 54 (2) ◽  
pp. 280-289 ◽  
Author(s):  
I. W. J. Still ◽  
N. Plavac ◽  
D. M. McKinnon ◽  
M. S. Chauhan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Conjugated Systems ◽  
Organic Sulfur Compounds ◽  
Nmr Data ◽  
Nuclear Magnetic Resonance Spectra ◽  
Related Series ◽  
Sulfur Containing ◽  
C Nmr

13C nmr data have been obtained for a series of 2- and 4-pyrones and pyridones, and their sulfur-containing analogues. Correlations have been observed between the nature of the ring hetero-atom and the chemical shift difference (Δδ) for the Cα and Cβ carbons in these conjugated systems. No significant correlation, however, appears to exist between the chemical shifts of the C=O and C=S groups. Substituent chemical shift (s.c.s.) effects for various simple substituents are compared with those in related series of compounds.

The High Resolution NMR Spectra of Pesticides. II. The DDT-Type Compounds

1969 ◽  
Vol 52 (5) ◽  
pp. 1074-1092 ◽  
Author(s):  
L H Keith ◽  
A L Alford ◽  
A W Garrison
Keyword(s):  
Nuclear Magnetic Resonance ◽  
High Resolution ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Aromatic Rings ◽  
Nuclear Magnetic Resonance Spectra ◽  
High Resolution Nmr ◽  
Related Compounds ◽  
Deshielding Effect

Abstract The high resolution nuclear magnetic resonance spectra of the DDT class of pesticides and related compounds are discussed, including a study of the resonances of the aromatic protons as they are affected by various substiluents. The CCl3 moiety on the α-carbon strongly deshields the ortho protons on the aromatic rings, and this deshielding effect is greatly enhanced by substitution of a chlorine ortho rather than para on the aromatic ring. These deshielding effects are explained by a consideration of the electronegativity of the substituents and the stereochemistry of the molecule. The chemical shifts and coupling constants are tabulated.

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