Mono-substituted pyridines, calculation

Kamienska-Trela et al performed DFT calculations of /(C,C) coupling constants for variously mono- and disubstituted pyridine N-oxides and mono-substituted pyridines. The DFT data reproduced very well the experimental coupling values and revealed that the FC contribution is the dominating factor which governs the magnitude of the CC coupling across one bond. 

Despite the fact that d is not a simple quantity, but a function oi AH and A S, its variation with change of structural parameters obeys a simple relationship, as may be seen from the additivity of A O values. This term is used here in the sense that the thermodynamic quantities for disubstituted compounds may be predicted from the changes produced when single substituents are introduced separately. The free energies of ionization of some methyl disubstituted pyridines, anilines and phenols are shown in Table 4 (to which we shall refer in detail later). From A G values for the parent and mono-substituted compounds it is possible to estimate A G values for disubstituted compounds. Thus, from the A G values for p ridine and the picolines, the following increments are calculated 2-methyl 1 01, 3-methyl 0-56, 4-methyl 1 03. 

Dipole moments for several mono- and disubstituted pyrrolo[2,3-3]pyridines, 26, have been calculated using the PM3 method <1997JFA2345>. The values range from approximately 1 D for 3-halo-substituted compounds to 5.14 D for the 3-nitro deriv ative (see Table 1, Section 10.06.2.2). 

Method of Nys and Rekker The Nys and Rekker method [53,54] has been developed for mono- and di-substituted benzenes. The substituents considered are halogen atoms and hydroxyl, ether, amino, nitro, and carboxyl groups, for which contributions have been calculated by multiple regression analysis (s = 0.106, r = 0.994, F = 1405). Rekker discusses the extension of his approach to other compound classes, such as PAHs, pyridines, quinolines, and isoquinolines. 

The basicities in water and in aqueous surfactant solution of another 15 aryl-Pl(pyrrolidino) [(NC4Hs)3P=N-Ar] and aryl-Pl(dimethylamino) [(NMe2)3P=N Ar] phosphazenes (Ar = mono or di substituted phenyl rings) have been measured and correlated with previous data using acetonitrile and THE. A comparison with other bases such as guanidines, amines and pyridines showed that, in all cases, the phosphazenes were the strongest bases. The results confirmed earlier conclusions about the partly ylidic character of the NP double bond. Density functional theory calculations have shown that the phosphazenes (41) and (42) are very powerful neutral organic superbases at the site marked by an asterisc (the calculated pA a values in acetonitrile were 44.8 and 37.8, respectively). ... 

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