| Popis: |
The CNDO/2 MO and INDO MO methods were used to study the molecular electronic structure of the bicyclic molecules derived by transannular interaction of the amide groups in two isomeric dioxodiazacyclo-decanes. A physical model based on the invariance of the MO's with respect to linear transformation of the basis set allowed to determine a functional relation between the bond atomic population M C-N and r C-N (transannular) in a set of closely related lactams (dioxodiazacycloalkanes). Further, the stabilities of a set of cyclopeptides as determined by Shemyakin et al. allowed to calculate a minimum value of M C-N and a maximum transannular distance r C-N beyond which is not possible the transannular interaction between the amide groups in this kind of molecules. These approaches were used together to provide quantitative results which enable to account for the different behaviour of 6,10-dioxo-l,5-diazacyclodecane and 4,10-dioxo-1,5-diazacyclodecane towards ring contraction reactions. |
