Free energy distribution between groups

FIGURE 2.3 Linear free energy relationship between the distribution constant of enol form (Kde) or keto form (K k) of n-alkyl substituted P-diketones and the carbon numbers of the alkyl group. 

In contrast to apportioning the standard free energy between different groups in the solute molecule, the standard free energy can also be dispensed between the different types of forces involved in the solute/phase-phase distribution. This approach has been elegantly developed by Martire et al. [13]. In a simplified form, the standard free energy can be divided into portions that result from the different types of interaction, e.g.,... 

Asymmetrically substituted thioamides 24e-h exist in equilibrium between rotamers 24-1 and 24-11. The NMR spectrum of AT-benzyl-iV-methylmeth-acrylthioamide 24e showed the distribution of 24e-I 24e-II was 55 45 (Scheme 13 and Table 8) [47]. The free energy of activation of the rotational barrier was measured by the temperature-dependent NMR spectra in DMSO at various temperatures. The free energy of activation of the rotation of the (C=S)-N bond could be estimated as 22.7 kcal mokh Furthermore, Table 8 shows the ratio of I II, and all three thioamides 24f-h favor the conformation I with the situation that a benzyl group was placed closely to the thiocarbonyl group on... 

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