离子基碳－氧键断裂能量的研究（Ⅱ）──负离子基的键能

Studies on Enthalpies of Carbon Oxygen Bond Cleavage in Radical Ions(Ⅱ)──Bond Energies of Radical Anions

合成了３个系列芳香类含碳一氧键的化合物，用循环伏安法测定了相关的氧化还原电势，通过热力学循环首次估测了负离子基的碳—氧键的断裂能量（ΔＨ（ｃｌｅａｖ）［Ｃ－Ｏ］（·－））．结果表明：得到１个电子形成负离子基可以活化碳—氧键．这与具有相同结构的正离子基的情况是一致的，但其活化程度略小．相关分析表明：ΔＨ（ｃｌｅａｖ）［Ｃ－Ｏ］（·－）ｖｓ（ΔＥ（ｒｅｄ）［Ｃ－Ｏ］＋ΔｐＫａ［ＨＡ］）和ΔＨ（ｃｌｅｓｖ）［Ｃ－Ｏ］（·＋）ｖｓ．（ΔＢＤＥ－ΔＥ（ｏｘ）［Ｃ－Ｏ］）均呈线性．讨论了负离子基和正离子基及其母体化合物中键的特征，并与文献中有关的键能数据进行了比较。

Three series of fossil model compounds were synthesized and their oxidation and reduction potentials were determined by CV using BAS-100B electrochemical analyzer.Thermodynamic cycles have been developed to determine the enthalpies of the carbon─oxygen bond cleavage of the derived radical ions.It was found that the carbon─oxygen bond is similarly activated in a thermodynamic sense by introducing an electron to the system as what was observed previously in a structurally similar radical cation, except smaller in amplitude. The carbon─oxygen bond cleavages of radical ions are all exothermic or slightly endothermic, implying a low barrier for rupture of the sessile bond,This is important to fossil fuel industry for improving traditional coal gasification routine and selecting new fragmentation path.Correlation analysis shows that plots of △Hcleav[C─O]+vs.( △BDE─△Eox[C─O]) and △Hcleav[C─O]-vs.( △Ered[C─O]+△pKa[HA]) are linear.Bond properties in relation to their structural features for both radical ions and their parent molecules are discussed and are compared with the relevant bond energy data in literature.