ROTATIONAL BARRIERS, MOLECULAR MODELS & STEREOSELECTION

构象、立体选择和分子间相互作用问题 都是理解生物学作用的关键要素 重要的化合物，以及它们的合成设计。从长远来看 目标是获得关于这些问题的足够信息，以便更多 可以开发用于分子建模的有效程序，并且 分子之间的非共价相互作用可能会得到更好的理解。这个 计划是进行实验和理论研究，并 将两种方法的结果以如下方式详细地联系起来 有可能。立体声和声学的决定因素问题 还将审查地区选举。 具体地说，建议确定形成热的 C4-Cl2单环内酯类化合物的量热测定及其性质研究 构象。这些数据将提供第一次真正的电流测试 内酯的分子力学力场，应该允许更好的 要开发的力场。内酯类化合物的酸性和碱性 还将研究环尺寸的函数。此外，非共价键 将利用静电势和 相关数量。这是半经验模型中常用的模型。 有道理。三维静电势的详细计算 将执行使用大基数集的地图，并将与 包含点电荷、偶极和四极的模型。后者将 由波函数得到。 其他拟议的研究包括对环中区域选择的研究 螺环环氧化物的开环和具有内环的环氧化物 亲核主义者。将继续对以下系统进行构象研究 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.