Proton magnetic resonance studies of rotational isomerism around the 2-propyl-nitrogen bond in some thionamides

1970 ◽  
Vol 35 (4) ◽  
pp. 1019-1022 ◽  
Author(s):  
Thomas H. Siddall ◽  
William Esley. Stewart
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Rotational Isomerism ◽  
Magnetic Resonance Studies ◽  
Nitrogen Bond

Proton Magnetic Resonance Studies of Rotational Isomerism in Halotoluene Derivatives. IX. Rotational Barriers and Conformational Energy Differences in α,α,α′,α′,α″,α″, 2,4,6-Nonachloromesitylene

1973 ◽  
Vol 51 (13) ◽  
pp. 2110-2117 ◽  
Author(s):  
J. Peeling ◽  
B. W. Goodwin ◽  
T. Schaefer ◽  
J. B. Rowbotham
Keyword(s):  
Magnetic Resonance ◽  
Carbon Disulfide ◽  
Proton Magnetic Resonance ◽  
Methylene Chloride ◽  
Activation Parameters ◽  
Rotational Isomerism ◽  
Conformational Energy ◽  
The Other ◽  
Free Energies ◽  
Magnetic Resonance Studies

The activation parameters for the rotation of the dichloromethyl groups in the two conformations of α,α,α′,α′,α″,α″,2,4,6-nonachloromesitylene are reported for solutions in toluene-d8 and in methylene chloride. In addition, free energies of activation are given for solutions in bromochloromethane, tri-chloroethylene, and in carbon disulfide. The free energies of activation are lower in the toluene solution than in the other solutions. The entropies of activation are near zero, perhaps slightly negative. The symmetrical conformation is more stable than the unsymmetrical one in all the solvents.

scholarly journals Proton Magnetic Resonance Studies of Rotational Isomerism in Halotoluene Derivatives. VI. Rotational Barrier and Conformational Energy Differences in α,α,2,3,6-Pentachlorotoluene

1971 ◽  
Vol 49 (7) ◽  
pp. 1085-1091 ◽  
Author(s):  
M. A. H. Stewart ◽  
T. Schaefer ◽  
H. M. Hutton ◽  
C. M. Wong
Keyword(s):  
Free Energy ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Energy Difference ◽  
Rotational Isomerism ◽  
Free Energy Difference ◽  
Magnetic Resonance Studies ◽  
Shape Fitting ◽  
Carbon Carbon Bond ◽  
Entropy Of Activation

Rotation by π radians about the sp2–sp3 carbon–carbon bond of the dichloromethyl group in α,α,2,3,6-pentachlorotoluene interconverts the two conformations which are characterized by coplanarity of the aromatic ring with the C—H bond of the sidechain. The ring protons undergo effective nonmutual exchange during this rotation. The rate of rotation as a function of temperature is extracted by line-shape fitting of the ring p.m.r. spectra. The rotation is characterized by a negative entropy of activation. The free energy difference between the two conformations is 50 ± 20 cal/mol at 240 °K.

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