中文摘要：

采用密度泛函方法研究了十二胺在气相、苯、乙酸、乙醇及水中的分子构型、电荷分布以及前线轨道。首先采用B3LYP／6．31G（d，p）及B3LYP／6-311＋＋G（d，p）进行优化，采用自洽反应理论（SCRF）的极化连续介质模型（PCM）进行不同溶剂条件下的优化并进行自然键轨道（NBO）分析。结果表明，对比气相条件下，十二胺分子的几何构型发生了微弱变化，这种变化随着溶剂介电常数的增加长程稳定性增强，溶剂化效应使前线轨道中HOMO趋于比LUMO更稳定，NBO分析表明溶剂化能主要来源于LP（1）N38→π＊C32-C33。随着溶剂介电常数的增加，十二胺分子采用B3LYP／6—31＋G（d，p）的△EHOMO-ELUMO由气相-0．23773a．u至水相中-0．25120a．u，溶剂化能-13．36kcal／mol，采用B3LYP／6—311＋＋G（d，p）的△EHOMO-ELUMO由气相-0．22755a,u至水相中-0．24004a-u，溶剂化能-13．02kcal／mol，溶剂化能趋于稳定，表明十二胺分子的溶剂化效应采用B3LYP／6．31＋G（d，p）构型趋于稳定。采用B3LYP／6—31＋G（d，p）对十二胺与水分子氢键超分子结构进行了研究，利用分子静电势（MEP）进行氢键及反应活性位分析，结果表明氢键作用是引起十二胺分子结构和性质变化的主要原因。研究结果对十二胺捕收剂在溶剂条件下对矿物的浮选机理认识具有一定的理论意义。

英文摘要：

Density functional theoretical calculations were performed to study the molecular geometries, electronic distribution of orbits and frontier orbits of dodecylamine in vacuum state, in solvents of benzene, aceticacid, ethanol and water. The molecular structure of dodecylamine in vacuum state was first optimized at B3 LYP/6-31＋G（d,p） and B3 LYP/6-311＋＋G（d,p） levels, respectively. The molecular structure of dodecylamine in different solvents was fully optimized and analyzed with NBO using self-consistent reaction field （SCRF） at B3 LYP/6-31＋G（d,p） and B3 LYP/613114＋G（d,p） levels, respectively. Results show that the long distance stability increases with the increase of the dielectric constants of solvents, the stability of HOMO is larger than that of LUMO. By B3 LYP/6-31 G＋（d,p） method, which mainly comes from its LP（1） N3s→π＊C32-C33 by NBO analysis. The gap of EHOMO-ELUMO increases from -0.23773 a.u in vacuum state to -0.22755 a.u in water, the solvation energy is -13.36 kcal/mol in water. By B3 LYP/6-311 G＋＋（d,p） method, the gap of EHOMO-ELUMO increases from -0.22755 a.u in vacuum state to -0.24004 a.u in water, the solvation energy is -13.02 kcal/mol in water. It is observed that the solvation energies is stable, meaning the geometry of dodecylamine is stable at B3 LYP/6-31 G＋（d,p） level in case of solvent effects. The super-molecular structure of dodecylamine and water connected by hydrogen bonding was constructed at B3 LYP/6-31 G＋（d,p） level, molecular electrostatic potential （MEP） was used to study the hydrogen bonding and reaction activity sites. Results show that the hydrogen bonding interaction may induce a large variation of the structure and properties of dodecylamine. The feasibility of using the theoretical analysis involving solvent effects to check the flotation mechanism of dodecylamine collector is discussed.