THEORETICAL APPROACH TO THE THERMOCHEMISTRY OF GEMINAL INTERACTIONS IN XY(2)H(N) COMPOUNDS (X=C, N, O, SI, P, S, Y=NH2,OH, F, SIH3, PH2, SH) - THE GENERALIZED ANOMERIC EFFECT REEXAMINED

The enthalpies of formation of a series of XY(2)H(n) compounds have be en calculated using the homodesmic reaction XY(2)H(n) + CH(3)XH(n)CH(3 ) --> 2CH(3)XH(n)Y with total energies computed at the MP2 = FULL/6-31 G(d,p)//MP2 = FULL/ 6-31G(d,p) level. The unifying concept of thermody namic stabilization energy allowed us to estimate the magnitude of the interaction between two substituents attached to a common saturated c enter. The so-called geminal interaction varies from 9 to -4 kcal mol( -1) in the series of compounds considered in this work. The generalize d anomeric effect which is only a part of the geminal interaction cann ot be used for rationalizing the thermochemistry of reactions involvin g XY(2)H(n) compounds.