The nature of superacid electrophilic species in HF/SbF(5): a density functional theory study

Pierre M Esteves; Alejandro Ramírez-Solís; Claudio J A Mota

doi:10.1021/ja011151k

The nature of superacid electrophilic species in HF/SbF(5): a density functional theory study

J Am Chem Soc. 2002 Mar 20;124(11):2672-7. doi: 10.1021/ja011151k.

Authors

Pierre M Esteves¹, Alejandro Ramírez-Solís, Claudio J A Mota

Affiliation

¹ Instituto de Química, Departamento de Química Orgânica, Universidade Federal do Rio de Janeiro, Cidade Universitária CT Bloco A, 21949-900, Rio de Janeiro, Brazil.

PMID: 11890818
DOI: 10.1021/ja011151k

Abstract

A density functional theory study at the B3LYP/6-31++G** + RECP(Sb) level of the HF/SbF(5) superacid system was carried out. The geometries of possible electrophilic species, such as H(2)F(+).Sb(2)F(11)(-) and H(3)F(2)(+).Sb(2)F(11)(-), were calculated and correspond with available experimental results. Calculations of different equilibrium reactions involving HF and SbF(5) allowed the relative concentration of the most energetically favorable species present in 1:1 HF/SbF(5) solutions to be estimated. These species are H(+).Sb(2)F(11)(-), H(2)F(+).Sb(2)F(11)(-), H(3)F(2)(+).Sb(2)F(11)(-), and H(4)F(3)(+).Sb(2)F(11)(-), which correspond to 36.9, 16.8, 36.9, and 9.4%, respectively. Calculations of the acid strength of the electrophilic species were also performed and indicated that, for the same anion, the acid strength increases with the solvation degree. The entropic term also plays a significant role in proton-transfer reactions in superacid systems.