ROTATIONAL BARRIERS, MOLECULAR MODELS & STEREOSELECTION

构象、立体选择和分子间相互作用的问题 是理解生物学作用的关键因素， 重要的化合物，并在其合成的设计。 长期 我们的目标是获得有关这些问题的足够信息， 可以开发用于分子建模的有效程序，并且 可以更好地理解分子之间的非共价相互作用。 的 计划进行实验和理论研究，并 将两种方法的结果详细地联系起来， 可能 决定立体声的因素问题， 还将审查区域选择。 具体而言，建议确定的形成热的 C_4-C_2单环内酯维斯热测量，并研究其 构象 这些数据将提供第一个真实的测试电流 分子力学力场的内酯，并应允许更好的 要发展的力场 内酯的酸碱性作为一种 还将研究环尺寸的函数。 此外，非共价 将利用静电势研究相互作用， 相关数量。 这是一个常用的半经验模型， 道理啊 三维静电势的详细计算 将进行使用大基组的地图，并将与 包含点电荷、偶极和四极的模型。 后者将 可以从波函数中得到。 其他提议的研究包括环中区域选择的研究 螺环环氧化物和具有内部结构的环氧化物的开环 亲核试剂 构象研究将继续系统，如 乙烯基乙醛和苯乙醛。

Problems of conformation, stereoselection and intermolecular interactions are key elements in both the understanding of the role of biologically important compounds, and in the design of their synthesis. The long term goal is to gain enough information concerning these problems so that more effective procedures for molecular modeling may be developed, and that non-covalent interactions between molecules may be better understood. The plan is to carry out both experimental and theoretical studies, and to relate the results of the two approaches in as detailed a fashion as possible. The problem of the factors determining stereo- and regioselection also will be examined. Specifically, it is proposed to determine the heats of formation of the C4-Cl2 monocyclic lactones vis calorimetric measurements and to study their conformations. These data will provide the first real test of current molecular mechanics force fields for lactones, and should allow better force fields to be developed. The acidity and basicity of lactones as a function of ring size also will be studied. In addition, non-covalent interactions will be studied making use of electrostatic potentials and related quantities. This is a commonly used model in a semiempirical sense. Detailed calculations of three dimensional electrostatic potential maps using large basis sets will be carried out, and will be related to models containing point charges, dipole and quadrupoles. The latter will be obtained from the wave functions. Other proposed studies include a study of regioselection in the ring opening of spirocyclic epoxides, and of epoxides having internal nucleophiles. Conformational studies will be continued for systems such as vinylacetaldehyde and phenylacetaldehyde.