Acidities of closo-1-COOH-1,7-C2B10H11 and Amino Acids Based on Icosahedral Carbaboranes

详细信息    查看全文

• 作者：Juan Z. D谩valos ; Javier Gonz谩lez ; Roc铆o Ramos ; Drahom铆r Hnyk ; Josef Holub ; J. Arturo Santaballa ; Mois茅s Canle-L. ; Josep M. Oliva
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：April 17, 2014
• 年：2014
• 卷：118
• 期：15
• 页码：2788-2793
• 全文大小：310K
• 年卷期：v.118,no.15(April 17, 2014)
• ISSN：1520-5215

文摘

Carborane clusters are not found in Nature and are exclusively man-made. In this work we study, both experimentally and computationally, the gas-phase acidity (measured GA = 1325 kJ路mol^鈥?, computed GA = 1321 kJ路mol^鈥?) and liquid-phase acidity (measured pK_a = 2.00, computed pK_a = 1.88) of the carborane acid closo-1-COOH-1,7-C₂B₁₀H₁₁. The experimental gas-phase acidity was determined with electrospray tandem mass spectrometry (ESI/MS), by using the extended Cooks kinetic method (EKM). Given the similar spatial requirements of the title icosahedral cage and benzene and the known importance of aminoacids as a whole, such a study is extended, within an acid鈥揵ase context, to corresponding ortho, meta, and para amino acids derived from icosahedral carborane cages, 1-COOH-n-NH₂-1, n-R with {R = C₂B₁₀H₁₀, n = 2, 7, 12}, and from benzene {R = C₆H₄, n = 2, 3, 4}. A remarkable difference is found between the proportion of neutral versus zwitterion structures in water for glycine and the carborane derived amino acids.