Organic Orbital Theory-Discovery of New Concepts in Basic Organic Chemistry.

以下三个项目已经完成。π面非对映选择预测的新理论模型。与传统的π-面非对映选择过渡态模型（Felkin-Anh和Cieplak模型）的主张相反，从理论上证明了亲核羰基加成过渡态中涉及初始键的反周面效应并不是决定面非对映选择的必要条件。基于Salem-Klopman方程和前沿轨道理论，提出了一种预测π面非对映选择的新量子化学模型。该模型，即外边界轨道扩展模型（EFOE模型），对大多数环酮的氢化物还原的面非对映选择预测是非常有效的。有机系统与蛋白质弱相互作用的定量分析。利用硒核自旋（1/2）的特殊性质，研究了16族元素氢键（X…H-Y (X=O， S, Se， Te和Y=O， C)）和Se…Z （Z=N， O， F）非键吸引相互作用的性质和强度。结论是，在所有这些情况下，相互作用都不是静电的，而主要是供体-受体型轨道相互作用。在相关项目中，我们检测并表征了蛋白质中的新型弱原子相互作用，如C-S…O， S-S…O和C=O…S。这些相互作用主要是供体-受体型，具有很强的键指向性。基础有机化学问题的再探讨尽管氟苯在亲电取代中比苯的反应性更强，但由于卤素的吸电子性质，氟苯被普遍认为是失活的。对卤代苯中π-体系的轨道相互作用进行了定量分析，得出单取代苯的反应活性取决于π-轨道（π1）的最低能级，而不取决于π2或π3的前沿能级。因此，卤代苯（Cl, Br， I）由于其供电子性质而失活。用自然键轨道（NBO）分析了顺式效应和扭切效应的问题。少

The following three projects have been completed.1. New Theoretical Model for the Prediction of π-Facial Diastereoselection.Contrary to the claim of the conventional transition state models of π-facial diastereoselection (Felkin-Anh and Cieplak models), it is theoretically proven that the antiperiplanar effects involving the incipient bond in the transition state of nucleophilic carbonyl addition are not essential to dictate facial diastereoselection. Based on the Salem-Klopman equation and the frontier orbital theory, a new quantum chemical model for the prediction of π-facial diastereoselection has been proposed. This model, the exterior frontier orbital extension model (the EFOE Model) is found to be very effective for the prediction of facial diastereoselection of the hydride reduction of most cyclic ketones.2. Quantitative Analysis of Weak Interaction in Organic Systems and Proteins.Utilizing the specific property of selenium nuclear spin (1/2), the nature and the strength of weak … More interactions in hydrogen bonds involving Group 16 elements (X…H-Y (X=O, S, Se, Te and Y=O, C) ) and Se…Z (Z=N, O, F) non-bonded attractive interactions have been investigated. It is concluded that in all these cases the interactions are not electrostatic, but largely the donor-acceptor type orbital interaction. In a related project, we have detected and characterized new type of weak atomic interactions in proteins, such as C-S…O, S-S…O and C=O…S.These interactions are mainly the donor-acceptor type with strong bonding directionality.3. Reinvestigation of the Problems in Basic Organic ChemistryIt is generally accepted that halobenzenes are deactivated because of e-withdrawing nature of halogens, in spite of the fact that fluorobenzene is more reactive than benzene in electrophilic substittution. Quantitative analysis of orbital interactions of the π-systems in halobenzenes, it is concluded that the reactivity of mono-substittuted benzenes are dependent on the energy level of the lowest occupied π-orbital (π1) and not of the frontier orbitals (π2 or π3). Halobenzenes (Cl, Br, I) are therefore deactivated because of their e-donating property. The problems of cis-effect and gaucheeffect have also been investigated by natural bond orbital (NBO) analysis. Less