Protonation of benzo-18-crown-6: Extraction and DFT study

0355840 - ÚMCH 2011 RIV DE eng J - Journal Article
Toman, Petr - Makrlík, E. - Vaňura, P. - Kašička, Václav
Protonation of benzo-18-crown-6: Extraction and DFT study.
Zeitschrift für Physikalische Chemie : International Journal of Research in Physical Chemistry & Chemical Physics. Roč. 225, č. 2 (2011), s. 265-270. ISSN 0942-9352
R&D Projects: GA ČR(CZ) GAP205/10/2280
Institutional research plan: CEZ:AV0Z40500505; CEZ:AV0Z40550506
Keywords : protonation * nitrobenzene * benzo-18-crown-6
Subject RIV: CD - Macromolecular Chemistry
Impact factor: 1.568, year: 2011

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H3O+(aq) + 1•Na+(nb) reversible arrow 1•H3O+(nb) + Na+(aq) taking place in the two-phase water-nitrobenzene system (1 = benzo-18-crown-6, aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex(H3O+, 1•Na+)=-0.8±0.1. Further, the stability constant of the 1•H3O+ complex in water-saturated nitrobenzene was calculated for a temperature of 25°C as log βnb(1•H3O+)=6.3±0.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the 1•H3O+ cationic complex species was derived. In this complex, the hydroxonium ion H3O+ is bound by three strong linear hydrogen bonds to one (Ar–O–CH2) ethereal oxygen and two (CH2–O–CH2) ethereal oxygen atoms of the parent crown ligand 1. The interaction energy was found to be -401.4kJ/mol, confirming the formation of the considered complex 1•H3O+.
Permanent Link: http://hdl.handle.net/11104/0194518