Results 211 to 220 of about 39,711 (263)

Vicinal Fluorine–Proton Coupling Constants

Journal of Magnetic Resonance, 1998
The angular dependence and the effect of individual substituents upon the NMR vicinal fluorine-proton couplings 3JFH have been studied using data sets of experimental and calculated couplings. Coupling constants for a series of fluoroethane derivatives, CHXF-CH3 and CH2F-CH2X (X = CH3, NH2, OH, and F), were calculated by means of the SCF ab initio and ...
, San Fabian J, , Guilleme, , Diez
openaire   +2 more sources

Proton-proton coupling constants in conjugated dienes

Molecular Physics, 1963
The proton resonance spectra of two conjugated dienes§ have been analysed to obtain spectral parameters, including 3 J's, 4 J's and in particular the three 5 J's, the coupling interactions across both double bonds. Some of the results differ from those of an earlier investigation and the reasons for this are discussed.
E.O. Bishop, J.I. Musher
openaire   +1 more source

Transoid Homoallylic Proton-Proton Coupling Constants

Australian Journal of Chemistry, 1989
Transoid homoallylic coupling constants (5JH,H) for six compounds (5,10-dihydroindeno[2,1-alindene and confertifolin derivatives) of fixed stereochemistry were determined and compared with calculated values. Magnetic equivalence limited discrete determination of 5Jtrans and 5Jcis to three of these compounds.
M Barfield, RJ Spear, S Sternhell
openaire   +1 more source

Molecular orbital calculations of the proton-proton coupling constants in nucleosides

Journal of Theoretical Biology, 1973
Abstract Molecular orbital calculations of proton-proton coupling constants are carried out for a number of nucleosides as a function of conformational characteristics of these compounds. The study of the role of the ring puckering and of the orientation of the exocyclic CH 2 OH group on the vicinal coupling constants of the ribose indicates the ...
C, Giessner-Prettre, B, Pullman
openaire   +2 more sources

A priori predictions of the rotational constants for protonated formaldehyde and protonated methanol

Chemical Physics Letters, 1986
Protonated formaldehyde and protonated methanol are candidate interstellar molecules and models for classes of protonated oxygen compounds. Ab initio molecular orbital theory has been used to compute rotational constants to guide spectroscopic searches both in the laboratory and in space. The ab initio results are empirically corrected to account for
D J, DeFrees, A D, McLean
openaire   +2 more sources

Taurocholate and Taurodeoxycholate: Gel Formation and Protonation Constants

Annali di Chimica, 2006
AbstractTaurocholate (TC) and taurodeoxycholate (TDC) in aqueous solutions, in the presence of sodium and hydrogen ions can give micellar products, even differently protonated. This phenomenon is investigated in this paper to explain whether the assumption of hydrogen ions is to attribute to the micellar aggregates, or to the protonation of ...
ANTONILLI, MARCO, BOTTARI, Emilio Giovanni, FESTA, Maria Rosa   +2 more
openaire   +2 more sources

Predicting Protonation Constants in Polyazaalkanes

Journal of Chemical Research, 1998
An easy model which allows to calculate protonation constants in polyamines containing n equivalent or near equivalent protonation sites from simple molecular analysis is reported.
José Manuel Lloris, Ramón Martínez-Mán˜ez, Eduardo Perales, Juan Soto   +3 more
openaire   +1 more source

Protonation rate constants of proline

Journal of Molecular Liquids, 1984
Abstract The rate constants for protonation reactions of proline positive ion and zwitterion have been measured using a modulated temperature chemical relaxation method. The results are contrasted with those obtained for amino acids.
M.A. Slifkin, S.M. Ali
openaire   +1 more source

The effect of substituents on geminal proton–proton coupling constants

Canadian Journal of Chemistry, 1967
A series of 2-benzyloxytetrahydropyrans bearing substituents at the ortho, meta, and para positions of the benzene ring have been synthesized. From the nuclear magnetic resonance spectrum of each compound, the geminal coupling constant (J) between the non-equivalent protons of the benzylic methylene group was determined.
Robert R. Fraser, Paul Hanbury, C. Reyes-Zamora   +2 more
openaire   +1 more source

Proton‐proton coupling constants in the unsubstituted pyrylium cation

Organic Magnetic Resonance, 1973
AbstractAn iterative analysis of the PMR spectrum of the title compound was performed and the calculated values of spectral parameters, relative chemical shifts, proton‐proton and direct carbon‐proton couplings are compared with those of pyridine.
L. Radics, Julia Kardos
openaire   +1 more source