Conformational free energy table

Table 3. Conformational free energy simulation of linear DPDPE. Changes in free energy and its components. Units kcal/mol...

Table 3.8. Comparison of Conformational Free-Energy Values for Substituents on Tetrahydropyran, 1,3-Dioxane, and 1,3-Dithiane Rings with Those for Cyclohexane...

The conformational free energies of some substituents in substituted cyclohexanes is given in the following table ... 

Table 10.2 (From book Topics in Stereochemistry by J. Hirsch, Interscience Publishers, New York) Conformational free energies of substituents in substituted cyclohexanes.

Analysis of the H-NMR spectra of the trimethyltetrahydro-l,2-oxazines 233,234, and 235 at — 35°C when nitrogen inversion is considered to be slow (see below) permits the conformational free energies of methyl substituents (Table XVII) to be estimated241 if the AGs Me value derived above is used. 

Table 10 Conformational Free Energies of Simple Alkyl Substituents on Rings...

Furthermore, when the solvation free energy is included, the difference in conformational free energy between the native and modeled loops is reduced as shown in Figure 1 for CDRLl. Similar plots were obtained for CDRL2 and CDRL3 (data not shown). The gap in energy observed when only side chains were optimized is reduced but still present for CDRLl (Table Ilb). There is no modeled CDRLl loop that had a lower conformational gas phase free energy than the native CDR loop. 

Tables II-IV. Five lowest conformational free energy loops for CDRLl, CDRL2 and CDRL3. The RMSD concerns backbone atoms N, CA, C.

For a monosubstituted oxane, the excess free enthalpy of the conformation with an axial substituent over the conformation with an equatorial substituent is, as we know by definition, the conformational free energy (CFE) of the substituent in oxane at this position. These values, possibly measured indirectly by utilizing intennediate compounds, are shown in Table 2.2. Equatorial conformations correspond to anti conformations in butane and methoxyethane, and the axial conformations (not represented) to gauche conformations. We can observe that the environment of derivative 2.20 is closest to that of the cyclohexane and that the CFE is of the same order. On the other hand, the presence of the cyclic oxygen lowers notably the CFE of derivative 2.19. The important point is the noteworthy increase in the CFE of compound 2.18, where the methyl group is close to the cyclic oxygen and possesses, on one side, an environment similar to that of methoxyethane. Let us look at the equilibrium (2.4) of the dimethylated derivative 2.21. 

Table 2.2 Conformational free energies of substituted oxanes (between 163-183 K in chlorinated solvents) (from Eliel et al. 1982) (reproduced with kind permission from the American Chemical Society).

Table 8.8. Conformational free energies for structural units of poly(6,8-dioxabi-cyclo 3,2,l oct-3-ene) (polyDBO)43 ...

There are several other methods available for determining conformational free energies.Values for many substituents in addition to those listed in Table 2.2 have been compiled. ... 

Table 2.2. Conformational Free Energies (—AG ) for Some Substituent Groups ...

Conformational free-energy values for many substituent groups on cyclohexane rings have been determined by NMR methods some are recorded in Table 3.5. Conformational free energies measured at low temperatures are not believed to vary much from their values at room temperature. 

A similar analysis of the hydrolysis of the esters 3 and 4 is possible. From Table 3.5 (p. 89), we see that the conformational free energy of the carbethoxy substituent is 1.2 kcal/mol. The cw-isomer should be placed above 4, then, by about... 

Conformational free-energy values for many substituent groups on cyclohexane have been determined by NMR methods some are recorded in Table 3.6. 

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