INFLECTION POINTS AND CHAOTIC BEHAVIOR IN SEARCHING THE CONFORMATIONAL SPACE OF CYCLONONANE

We have investigated the nature of two conformations recently discovered by others throughextensive searches of the conformational space of cyclononane. Although these conformations are indeed energy minima with the MM2 force field, they have only minute energy barriers separating them from previously known conformations of much lower energy and, therefore, have rather questionable significance. One of the new conformations is not a local energy minimum with some force fields. Explorations of conformational space are shown to benefit from a determination of the lowest energy transition states between all pairs of conformations. Convergence and stability problems in applying the full Newton-Raphson iteration method are investigated, and the key role of inflection points (particularly of the previously unappreciated “positive” type) on the energy hypersurface is presented. © 1990, American Chemical Society. All rights reserved.