Distance geometry global minima

Dmparison of various methods for searching conformational space has been performed cycloheptadecane (C17H34) [Saunders et al. 1990]. The methods compared were the ematic search, random search (both Cartesian and torsional), distance geometry and ecular dynamics. The number of unique minimum energy conformations found with 1 method within 3 kcal/mol of the global minimum after 30 days of computer processing e determined (the study was performed in 1990 on what would now be considered a / slow computer). The results are shown in Table 9.1. 

Nowek and Leszczynski used ab initio post-Hartree-Fock and DFT B3LYP calculations to resolve the problem of the structure of the Ge- OH2 complex274. The molecular geometries of the nonplanar 17 (Ci) and planar 18 (Cs) conformers were optimized at the DFT and MP2 levels of theory using TZP and TZ2P basis sets. The nonplanar complex 17 with a Ge - O distance of 2.214 A (MP2), 2.268 A (B3LYP) corresponds to a global minimum while complex 18 was found to be very weakly bound (if bound at all). 

Fig. 6.22. Several structures of the H h-HjCO addition, superimposed to show geometry changes over the course of the reaction. Geometries (6-31 -1- + G //6-31 + + G calculations) are labeled as follows (with the C-H distance given), ml charge dipole complex (Cjv), 3.2268 A a 2.5 A TS transition state, 2.0071 A b 1.6 A m2 global minimum, methanolate 1.1226 A...

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