Nuclear magnetic resonance spectra of the epihalohydrins: II. Spectral analyses and structural correlations for all the epihalohydrins

1970 ◽  
Vol 48 (7) ◽  
pp. 1046-1053 ◽  
Author(s):  
C. J. Macdonald ◽  
W. F. Reynolds
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Long Range ◽  
Propylene Oxide ◽  
Proton Magnetic Resonance ◽  
Dipole Moments ◽  
Coupling Constants ◽  
Vicinal Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra

Complete analyses of the proton magnetic resonance spectra of propylene oxide, epifluorohydrin, epibromohydrin, and epiiodohydrin shows that in all cases the cisoid coupling constants over four bonds are negative, and the transoid coupling constants positive. Dipole moments, together with the vicinal coupling constants of the CH—CH2X moiety, are used to establish the probable conformations for all the epihalohydrins. Conformational factors appear to obscure any possible relationship between substituent electronegativity and long-range coupling constants.

Molecular orbital calculations and 1H nuclear magnetic resonance spectra as indicators of internal rotational potentials in some methyl derivatives of styrene

1988 ◽  
Vol 66 (4) ◽  
pp. 584-590 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Glenn H. Penner
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Long Range ◽  
Coupling Constants ◽  
Molecular Orbital Calculations ◽  
Carbon Carbon Bond ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 1H nuclear magnetic resonance spectra of the α-methyl, cis and trans-β-methyl, 4-methyl, and β,β-dimethyl styrènes are analyzed to yield long-range proton–proton coupling constants. With the assumptin that the internal rotational potential for styrene in the gas phase is unaltered in solution, a consistent treatment of over 40 of the long-range coupling constants is given in terms of the known coupling mechanisms. Expectation values of sin2 θ, where θ is the angle of twist about the exocyclic carbon–carbon bond, are presented for these molecules. These are compared with theoretical potentials at the 6-31 G level of molecular orbital theory. The present data indicate rather larger average twist angles than those in the literature. The extrema (at θ = θ° and 90°) in the angle dependent long-range coupling constants appear to be rather smaller in magnitude than are theoretical values obtained from valence bond and molecular orbital approaches.

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.

Flavan derivatives. XXI. Nuclear magnetic resonance spectra, configuration, and conformation of flavan derivatives

1968 ◽  
Vol 21 (8) ◽  
pp. 2059 ◽  
Author(s):  
JW Clark-Lewis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Heterocyclic Ring ◽  
Coupling Constants ◽  
Vicinal Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
Configuration And Conformation ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Nuclear magnetic resonance spectra of 80 compounds belonging to several classes of flavan derivative have been analysed, and chemical shifts and coupling constants of heterocyclic ring protons and aromatic protons are tabulated and discussed. Compounds examined include flav-2-enes, flav-3-enes, 3-substituted flavanones and flavans, 2- and 4-substituted isoflavans, 3,4-disubstituted flavans, and flavan-4-ols. The geometrical configurations of substituents in the heterocyclic ring follow unequivocally from the magnitudes of the vicinal coupling constants.

High-Resolutjon nuclear-magnetic-resonance spectra of hydrocarbon groupings VI. The hydrogen spectra of carbon-13 substituted ethane, ethylene and acetylene

1962 ◽  
Vol 269 (1338) ◽  
pp. 385-403 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Resolution ◽  
Long Range ◽  
Experimental Results ◽  
Coupling Constants ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

High-resolution spectra have been obtained from the hydrogen nuclei of appropriate isotopic mixtures of ethane, ethylene and acetylene containing one or two magnetic 13 C nuclei. Analysis of these spectra has yielded the magnitudes of all but one of the possible inter - nuclear coupling constants in these molecules, including those between pairs of carbon nuclei. Where a given molecule has several coupling constants between pairs of the same type of nuclei the relative signs of these have also been determined. Discussion of the experimental results in terms of current theoretical treatments shows that in nearly all cases the contact, H 3 , term is the most important one in determining the magnitude of the coupling constants. Only in the case of the J CC and the long-range J ' CH coupling constants of acetylene does it appear to be necessary to consider appreciable contributions from other terms.

High-resolution nuclear-magnetic-resonance spectra of hydrocarbon groupings - V. ABCX spectra of vinyl fluoride and 3-methylbut-l-ene

1961 ◽  
Vol 263 (1312) ◽  
pp. 136-148 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Resolution ◽  
Coupling Constants ◽  
Vinyl Fluoride ◽  
General Properties ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Some general properties of ABCX -type spectra are discussed. It is shown that it is possible to deduce from such spectra the relative signs of all inter-nuclear coupling constants. Analyses are presented of the hydrogen (proton) spectra from the vinyl groups of vinyl fluoride and 3-methylbut-l-ene, and of the fluorine spectrum of the former molecule. It is shown that all HF coupling constants in vinyl fluoride are of the same sign as the cis and trans HH coupling constants.

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