title: Acidities of closo-1-COOH-1,7-C2B10H11 and amino acids based on icosahedral carbaboranes.
abstract: 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·mol(-1), computed GA = 1321 kJ·mol(-1)) and liquid-phase acidity (measured pKa = 2.00, computed pKa = 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-base 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.
authors.affiliation: Instituto de Química-Física "Rocasolano" , Consejo Superior de Investigaciones Científicas, Serrano 119, ES-28006 Madrid, Spain.
authors.forename: Juan Z
authors.initials: JZ
authors.lastname: Dávalos
authors.forename: Javier
authors.initials: J
authors.lastname: González
authors.forename: Rocío
authors.initials: R
authors.lastname: Ramos
authors.forename: Drahomír
authors.initials: D
authors.lastname: Hnyk
authors.forename: Josef
authors.initials: J
authors.lastname: Holub
authors.forename: J Arturo
authors.initials: JA
authors.lastname: Santaballa
authors.forename: Moisés
authors.initials: M
authors.lastname: Canle-L
authors.forename: Josep M
authors.initials: JM
authors.lastname: Oliva
mesh_terms: D001554:Benzene / Q000737:chemistry; D001880:Boranes / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015394:Molecular Structure; D013816:Thermodynamics
chemical_list: D001880:Boranes; D005740:Gases; D001554:Benzene; D005998:Glycine