胺類分子與甲酸分子間氫鍵之理論研究

我等採Gaussian 98 軟體，選用B3LYP/6-311 + G(2d, p)密度泛函數法對胺類一系列分子與甲酸之順型(syn form)及反型(anti form)之氫鍵結合之理論計算研究。計算結果發現甲酸之順型結構較反型結構與胺類分子形成之氫鍵較強，過去學理探討總以分子構形之總體能量高低，來判定分子形成氫鍵之強弱，為了更進一步探討氫鍵微觀結構上細節問題，我們採我等多年研發成功之半經驗「區域化鍵分佈分析法」計算鍵能、鍵次及庫侖吸引能，以驗証胺類分子因氮原子上甲基取代基增加後與甲酸形成之分子間氫鍵確實增強且多半有一致結果。惟取代基之位向受立體障礙之影響，使得鍵能及庫侖吸引能之計算結果非逐次增加現象。用能差法評斷氫鍵部份之強弱不僅應以總體自洽場(SCF)能量之能差高低作評定，亦應考量零點能修正、熵差(△S)及自由能差(△G)等值以便從宏觀立場判斷那一種氫鍵在不同溫度下易於分解等問題作探討。

關鍵字

分子間氫鍵；幾何優選；區域化鍵分佈分析法；鍵能；鍵次；庫侖吸引能；氫鍵解離

並列摘要

We selected B3LYP/6-311+G(2d,p), DFT type method in Gaussian 98 to study the hydrogen bonding formation problem between amines and formic acid with syn form or anti form. The calculated results show that hydrogen bonding effect in syn form structures are stronger than the related effect in anti form structures. In addition to using the total energy difference method for hydrogen bonding energy determination, we applied our newly developed semi-emperical ＂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 CH3 group on nitrogen. There are several bond energy and coulomb attraction terms alter there order due steric bindrance 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 (AS) and Gibbs energy difference 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

intermolecule hydrogen bonding ； geometical ； localized bond analysis method ； bond order ； bond energy ； coulomb attraction energy ； hydrogen bonding dissociation

國際替代計量

胺類分子與甲酸分子間氫鍵之理論研究

全文下載

主題瀏覽