南京大学结构化学双语课件CH6LEC2.ppt

Bound of the Energy Levels Theorem PROOF： 更复杂的体系 Alternant Hydrocarbons（交替烃） Properties of alternant Hydrocarbons Proof 交替烃的非键轨道 1. Charge Densities Charge Densities Charge Densities Charge Densities 2. Bond Orders Bond Orders Bond Orders Bond Order vs. Bond Length 3. Free Valence Free Valence 6.3 Charge Densities and Bond Orders Free Valence 4. Molecular Graph 1. Aromaticity, anti-aromaticity and 4n+2 rule 2. Resonance Energy, a Criteria of Aromaticity 参考结构 Resonance Energy of Some Typical Molecules 3. The Eight-parameter Scheme The Eight-parameter scheme The Eight-parameter scheme The Eight-parameter scheme The Eight-parameter scheme The Eight-parameter scheme 4. Five-parameter Scheme Charge Densities Charge Densities 上述权重值是通过对大量非芳香性分子的Ep进行最小二乘拟合得到的。 2.1716 (20) 2.1033 (21) 0.4358 (10) 2.0000 (22’) 0.4362 (11) 2.0699 (22) 0.4660 (12) 2.0000 (23) Bond Energy(b) Bond Type Bond Energy(b) Bond Type 并对每一种参考结构对于能量的贡献赋予一定的权重。 Total reference energy of the molecule can be calculated by counting the reference structure energies of each structure type. ER= 3E22+3E12= 3*(2.0699+0.4660) =7.61 RE = 8-7.61 = 0.39 (b) 分子共振能的计算与 Kekulé 结构的画法有关, 分子有多种Kekulé 结构时，RE 是各种 Kekulé结构共振能的平均值. ER= 4E22+E20 +2E12+ 4E11 = 13.128 ER= 3E22+2E21 +3E12+ 2E11 + E10 =13.1225 ER= 3E22+2E21 +3E12+ 2E11 + E10 =13.1225 ER = (13.128+2*13.1135)/3= 13.124 Ep = 13.68 RE = 13.68-13.124 = 0.56 (b) Define: REPE = RE/N Resonance Energies per Electron For Benzene REPE = 0.39/6 =0.065 For Naphthalene REPE = 0.55/10 = 0.055 3.62* 2.46* 4.51 3.36 3.68 2.00 RE(b) -0.004 haptalene -0.018 pentalene 0.027 biphenylene 0.020 anthracene 0.056 naphthalene 0.065 benzene REPE(H-S) Molecule J-T-H five-parameter Scheme Yuansheng Jiang (江元生） Au-Chin Tang （唐敖庆） Roald Hoffmann * 6.2 More about Energy Levels and Molecular Orbitals The BOUND and SUM of energy levels （能级的 “和” 与 “界”） Alternant Hydrocarbons （交替烃） The p energy levels of the conjugated hydr