Cycloalkylmethyl radicals. 2. Axial and equatorial cyclohexylmethyl and (4-alkylcyclohexy)methyl radicals. First determination of the conformational free energy difference of the CH2.cntdot. group

1985 ◽  
Vol 107 (22) ◽  
pp. 6315-6317 ◽  
Author(s):  
K. U. Ingold ◽  
J. C. Walton
Keyword(s):  
Free Energy ◽  
Energy Difference ◽  
Methyl Radicals ◽  
Free Energy Difference ◽  
Conformational Free Energy

Conformational analysis of 1,4-disubstituted cyclohexanes. III. trans-1,4-Di(trifluoroacetoxy)cyclohexane

1969 ◽  
Vol 47 (3) ◽  
pp. 429-431 ◽  
Author(s):  
Gordon Wood ◽  
E. P. Woo ◽  
M. H. Miskow
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Low Temperature ◽  
Conformational Analysis ◽  
Integration Method ◽  
Standard Free Energy ◽  
Energy Difference ◽  
Free Energy Difference ◽  
Conformational Free Energy

By the low temperature nuclear magnetic resonance integration method the standard free energy difference between the diequatorial and the diaxial forms of 1-H,4-H-trans-1,4-di(trifluoroacetoxy)-cyclohexane-d8 was found to be 77 ± 5 cal/mole. The conformational free energy (−ΔG0) of the trifluoroacetoxy group in the monosubstituted cyclohexane was 485 ± 4 cal/mole at the same temperature. The non-additivity of the −ΔG0 values is discussed in terms of transannular electrostatic interaction.

The conformational free energy difference for the trideuteromethyl substituent in cyclohexane

1980 ◽  
Vol 58 (23) ◽  
pp. 2714-2719 ◽  
Author(s):  
Harold Booth ◽  
Jeremy Ramsey Everett
Keyword(s):  
Free Energy ◽  
Room Temperature ◽  
Energy Difference ◽  
Axial Orientation ◽  
Free Energy Difference ◽  
Nmr Spectrum ◽  
Enthalpy Difference ◽  
Methyl Cyclohexane ◽  
Conformational Free Energy ◽  
C Nmr

Studies at 169 K to 194 K of the 13C nmr spectrum of cis-1-ethyl-[4-Me-2H3]-4-methylcyclohexane show that the conformational enthalpy difference −ΔH°(C2H3) is 1.82 ± 0.07 kcal mol−1 and the conformational entropy difference ΔS°(C2H3) is −0.28 ± 0.4 cal K−1 mol−1, values which do not differ significantly from the values for CH3. However, analysis of the room temperature 13C nmr spectrum of a mixture of cis-1-ethyl-4-methylcyclohexane and cis-1-ethyl-[4-Me-2H3]-4-methylcyclohexane showed that −ΔG°(C2H3) at 298 K is 11.89 ± 1.46 cal mol−1less than that for CH3, i.e. C2H3 has a slightly greater preference than CH3 for the axial orientation. The 13C nmr spectrum of a mixture of trans-1-ethyl-4-methylcyclohexane and trans-1-ethyl-[4-Me-2H3]-4-methyl-cyclohexane indicates that deuterium-induced 13C nmr isotope shifts, all upfield, occur across 1,2, 3, and 5 bonds.

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