Proton exchange in acid-base complexes induced by reaction coordinates with heavy atom motions

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• 作者：Saman Alavi^a ; ^{saman.alavi@nrc-cnrc.gc.ca} ; Mahdi Taghikhani^b
• 关键词：Proton exchange reactions ; Acid&ndash ; base complexes ; Atmospheric acid&ndash ; base complexes ; Acid&ndash ; water complexes ; Electronic structure calculations
• 刊名：Chemical Physics
• 出版年：2012
• 期刊代码：18_03010104
• 类别：ch
• 出版时间：19 June, 2012
• 卷：402
• 期：Complete
• 页码：105-112
• 文件大小：613 K

摘要

We extend previous work on nitric acid-ammonia and nitric acid-alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid-strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are <400 cm^鈭?. This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm^鈭?. Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.