胺類與硝酸組合分子系統氫鍵之理論研究

Theoretical study of inter-molecule hydrogen bond Between Amines and Nitric acid

陳成(Cheng Cheng) ； 吳龍興(Lung-Shing Wu) ； 劉敏憲(Chuan-Wen Liu) ； 劉權文(Min-Hsien Liu)

《化學》 61卷3期 (2003/09) Pp. 455-462

https://doi.org/10.6623/chem.2003047

摘要

近來我們使用GAUSSIAN 98 程式所提供密度泛函數理論(Density Functional Theory)之B3LYP/6-311 ++G(3df,2pd)計算方法，對於由胺類與硝酸所組成之分子系統進行幾何優選結構、能量、頻率等理論計算研究工作。並比較分析甲基取代對於此型組合分子系統所形成之氫鍵鍵結強弱的影響。過去學理探討除了以分子構型之整體能量與分解後能量間能差高低，來判斷分子形成氫鍵之強弱外，更進一步為探討氫鍵微觀結構上細節問題，採用我們多年研發成功之半經驗「區域化鍵分佈分析法」計算鍵能、鍵次及庫倫吸引能等，以驗證胺類分子因氮原子上甲基取代基增加後與硝酸形成之分子間氫鍵確實增強且多半有一致結果。但由於立體效應(Steric effect)的影響，使得計算結果非逐次增加現象。用能差法判斷氫鍵部分之強弱不僅應以總體自治場(SCF)能量高位作評定，亦應考量零點能修正、熵差(ΔS)及氫鍵自由能差(ΔG)等值以便從宏觀立場判斷那一種氫鍵在不同溫度下易否分解等問題作探討。

關鍵字

B3LYP/6-311++G(3df,2pd) ； 幾何優選 ； 推電子取代基 ； 分子間氫鍵 ； 區域化鍵分佈分析法 ； 氫鏈自由能差

並列摘要

Recently we selected the GAUSSIAN 98 software and use density functional theory (DFT) B3LYP/6-3 11++G(3df,2pd) calculation, to study the inter-molecule hydrogen bond between amines (N(CH_3)_nH_(3-n)) and nitric acid(HNO_3)conformers with processing geometrical optimization, energy analyzed and vibration calculation. The strengths of hydrogen bonding are particularly compared and analyzed for the various cases of the substituted methyl groups on N. In addition to discussing the total and decomposition energy, difference method for hydrogen bonding energy determination, we applied our newly developed semi-empirical ＂localized bond analysis method＂ to calculated the hydrogen bond order, bond energy and coulomb attraction energy with this analysis, most of the results identify that hydrogen bonding strength increased whenever substituting more H with CH_3 group on nitrogen. There were several bonding energy and coulomb .attraction terms alter their order due steric binding effect of increasing number of methyl groups. In the case of determination of hydrogen bonding strength by energy difference method, it is better to including the zero point correction term, entropy difference (ΔS) and hydrogen bond free energy difference(ΔG)values. For various temperature and with the macroscopic consideration these variables are also very important for the determination of hydrogen bonding dissociation.

並列關鍵字

B3LYP/6-311++G(3df,2pd) ； geometrical optimization ； activation groups ； inter-molecule hydrogen bond ； localized bond analysis method ； hydrogen bond free energy difference