Investigation of Factors Affecting Conformational Preference in Complex Haloethane Derivatives by Classical Energy Calculations

1973 ◽  
Vol 51 (16) ◽  
pp. 2659-2670 ◽  
Author(s):  
William F. Reynolds ◽  
Donald J. Wood
Keyword(s):  
Solvation Energy ◽  
Coupling Constants ◽  
Conformational Preference ◽  
Factors Affecting ◽  
Energy Calculations ◽  
Vicinal Coupling Constants ◽  
Classical Energy ◽  
Dipole Interactions ◽  
Related Compounds ◽  
Good Agreement

Classical energy calculations are used in combination with Abraham's electrostatic theory of solvation energy to estimate rotamer energy differences for haloethane derivatives. The calculations are tested by comparing experimental and calculated ΔE values for several di- and tetrahaloethanes. There is good agreement for chloro and bromo derivatives but poorer agreement for fluoro and iodo derivatives. ΔE values in solution are also estimated for l4 complex chloro- and bromoethanes which we have previously investigated by n.m.r. spectroscopy. The calculations generally parallel the experimental results as reflected by vicinal coupling constants. They are particularly useful for trends in conformational preference for closely related compounds and are used in conjunction with vicinal coupling constants to identify diastereomers produced by halogenation of alkenes. Steric interactions, dipole–dipole interactions and solvation energy are all important in determining conformational preference for complex haloethanes in solution.

Conformational analysis of acyclic compounds with oxygen–sulphur interactions. Part VI. Some 1-thioderivatives of 2-propanol and its acetates

1979 ◽  
Vol 57 (18) ◽  
pp. 2426-2433 ◽  
Author(s):  
Felipe Alcudia ◽  
José L. García Ruano ◽  
Jesús Rodríguez ◽  
Félix Sánchez
Keyword(s):  
Conformational Analysis ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Conformational Study ◽  
Conformational Preference ◽  
Methyl Group ◽  
Opposite Charge ◽  
H Nmr ◽  
Vicinal Coupling Constants

A conformational study of 1-X-2-propanol (X = SH, SMe, SOMe, SO2Me, +SMe2) and their O-acetyl derivatives (X = SMe, SOMe, SO2Me, and +SMe2) is reported. From the relative values of the vicinal coupling constants in 1H nmr spectra it has been possible to establish the conformational preference. When a density of opposite charge is supported by heteratoms, polar factors determined a great predominance of that conformation in which the sulphur function has an anti-relationship with respect to the methyl group. In thiol and thioethers the conformational preference is not so marked.

Effect of solvent and temperature upon the rotationally averaged vicinal coupling constants of some substituted 1,2-dibromoethanes

1969 ◽  
Vol 47 (8) ◽  
pp. 1295-1309 ◽  
Author(s):  
W. F. Reynolds ◽  
D. J. Wood
Keyword(s):  
Coupling Constants ◽  
Dipolar Interactions ◽  
Coupling Constant ◽  
Vicinal Coupling Constant ◽  
Factors Affecting ◽  
Relative Stabilities ◽  
Vicinal Coupling Constants ◽  
Solvent Dependence ◽  
Rotational Equilibrium ◽  
The Difference

The solvent dependence of vicinal coupling constants has been investigated for (1,2-dibromoethyl)-benzene and three of its 4-substituted derivatives and for threo- and erythro(1,2-dibromopropyl)benzene. The temperature dependence of the vicinal coupling constants of three of the compounds has also been investigated. The difference between the two vicinal coupling constants of (1,2-dibromoethyl)benzene is dependent upon solution dielectric constant (in non-aromatic solvents) while the sum of coupling constants remains constant. The relative stabilities of its three rotamers are deduced from this information. A polar substituent in the 4-position does not affect the rotational equilibrium in any predictable manner. The vicinal coupling constant of threo(1,2-dibromopropyl)benzene is strongly solvent dependent. The relative stabilities of its three rotamers are deduced from the observation that the vicinal coupling constant is temperature independent. The most stable rotamer of erythro(1,2-dibromopropyl)-benzene is deduced from the observation that the vicinal coupling constant is large and independent of solvent. Factors affecting conformational preference are deduced. It is concluded that dipolar interactions are as important as steric interactions.

Calculation of 15N NMR Parameters of Azides and Some Related Compounds. Revisiting the Methylation of Nitrous Oxide N2O

2011 ◽  
Vol 66 (10) ◽  
pp. 1079-1082 ◽  
Author(s):  
Bernd Wrackmeyer
Keyword(s):  
Experimental Data ◽  
Nitrous Oxide ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
15N Nmr ◽  
Experimental Conditions ◽  
Nmr Parameters ◽  
Related Compounds ◽  
Good Agreement

The results of a calculation of 15N NMR parameters (chemical shifts and coupling constants) of azides and related compounds are in reasonably good agreement with experimental data, even for triazadienyl fluoride, F-N3. The reaction between [CH3]+ and nitrous oxide, N2O, can yield either an O- or an N-methylated cation, [Me(N2O)]+. The calculated 15N NMR parameters clearly indicate that under the experimental conditions N-methylation to give [MeNNO]+ is preferred instead of the methoxydiazonium ion [MeONN]+ previously proposed.

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.

Conformation of 1,3-dimethoxypropane in the gas phase and in solution: rotational isomeric state simulation of NMR vicinal coupling constants

1995 ◽  
Vol 350 (2) ◽  
pp. 129-134 ◽  
Author(s):  
Akihiro Abe ◽  
Noriko Ichimura ◽  
Tetsuo Shinohara ◽  
Hidemine Furuya
Keyword(s):  
Gas Phase ◽  
Isomeric State ◽  
Coupling Constants ◽  
Rotational Isomeric State ◽  
Vicinal Coupling Constants

Conformational Studies on 1,3-Dioxepanes. Part IV. Applications of Geminal Coupling Constants to Conformational Analysis of 1,3-Dioxepanes

1974 ◽  
Vol 52 (24) ◽  
pp. 4062-4071 ◽  
Author(s):  
T. Bruce Grindley ◽  
Walter A. Szarek
Keyword(s):  
Conformational Analysis ◽  
Coupling Constants ◽  
Conformational Studies ◽  
Vicinal Coupling Constants ◽  
Geminal Coupling ◽  
Derivatives Of ◽  
Acetal Carbon

The magnitude of —OCH2O— group geminal H,H coupling contants, the size of the vicinal coupling constants, and the tenets of conformational analysis were used to establish that in solution the conformation of the 1,3-dioxepane rings in derivatives of 1,3:2,5-di-O-methylenemannitol and 2,5-O-methylenemannitol is predominantly the twist-chair in which the C2 axis passes through the acetal carbon.

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