Internal rotation in halogen derivatives of tolane X5C6CCC6X5 determined by molecular mechanics calculations

1990 ◽  
Vol 239 ◽  
pp. 205-207 ◽  
Author(s):  
Reidar Stølevik ◽  
Pirkko Bakken
Keyword(s):  
Molecular Mechanics ◽  
Internal Rotation ◽  
Molecular Mechanics Calculations ◽  
Derivatives Of

The conformational preference and barrier to internal rotation of an equatorial 3,5-dichlorophenyl group by the J method. Derivatives of cyclohexane, 1,3-dithiane, 1,3-dioxane, and 1,3-dioxolane

1979 ◽  
Vol 57 (3) ◽  
pp. 355-359 ◽  
Author(s):  
Ted Schaefer ◽  
Walter Niemczura ◽  
Werner Danchura
Keyword(s):  
Magnetic Resonance ◽  
Molecular Mechanics ◽  
Internal Rotation ◽  
Phenyl Ring ◽  
Proton Magnetic Resonance ◽  
Conformational Preference ◽  
Molecular Mechanics Calculations ◽  
X Ray ◽  
Carbon Carbon Bond ◽  
Derivatives Of

We report the preparation and the analysis of the phenyl ring proton magnetic resonance spectra of 3,5-dichlorophenylcyclohexane and of the 2-(3,5-dichlorophenyl) derivatives of 1,3-dioxane, 1,3-dithiane, and 1,3-dioxolane. With the exception of the dioxolanes these compounds exist predominantly as the equatorial isomers. The J method is used to show that the phenyl moiety prefers the conformation in which the α C—H bond lies in the phenyl plane. The predominantly twofold barriers to rotation about the carbon–carbon bond between the two ring systems are 2.0 ± 0.3, 0.4 ± 0.2, 2.2 ± 0.3, 0.85 ± 0.3 kcal/mol for these compounds, in the order given above. The low value for the barrier in the 1,3-dioxane derivative agrees reasonably well with molecular mechanics calculations and with the results of calorimetric and X-ray studies on equatorial 2-phenyl-1,3-dioxane.

An X-ray and conformational study of the α-chloro derivatives of 5,7-dihydro-1,11-dimethyl-6H-dibenzo[a,c]cyclohepten-6-one

1994 ◽  
Vol 72 (6) ◽  
pp. 1481-1488
Author(s):  
Robert R. Fraser ◽  
Corinne Bensimon ◽  
Neil C. Faibish ◽  
Fanzuo Kong
Keyword(s):  
Molecular Mechanics ◽  
Benzene Ring ◽  
Membered Ring ◽  
Single Atom ◽  
Conformational Study ◽  
Molecular Mechanics Calculations ◽  
X Ray ◽  
Chloro Derivatives ◽  
Torsional Angles ◽  
Derivatives Of

The crystal structures for four α-chloro derivatives 2–5 of the titled ketone 1 have been determined, confirming their earlier assignments of stereochemistry. Variations in the conformations of 2–5 suggested some flexibility in the central seven-membered ring. Molecular mechanics calculations of the changes in energy as a function of the internal torsional angles at the carbonyl of these chloro derivatives indicated the ring flexibility to be comparable to that of cyclohexanone. In the three compounds containing an axial chlorine the distance between the chlorine atom and two of the carbon atoms of the more remote benzene ring was 3.2 ± 0.1 Å, suggesting the value for the thickness of a benzene ring may be significantly smaller than the accepted value when it is interacting with a single atom.

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