title: A cryosolution infrared and ab initio study of the van der Waals complexes of cyclopentene with hydrogen chloride and boron trifluoride.
abstract: The formation of weak molecular complexes of cyclopentene with HCl and BF3, dissolved in liquid argon is investigated using infrared spectroscopy. Evidence is found for the formation of 1:1 complexes in which the Lewis acid under study binds to the CC double bond. At higher concentrations of HCl, weak absorption bands due to 1:2 species are also observed. From spectra recorded at different temperatures between 92 and 127 K, the complexation enthalpies for CP.HCl and CP.BF3 are determined to be -9.5(3) and -16.1(9) kJ mol-1, while for CP.(HCl)2 a value of -17.0(6) kJ mol-1 is obtained. For the 1:1 and 1:2 complexes, structural and spectral information is obtained from ab initio calculations at the MP2/6-31+G(d) level. Using free energy perturbation Monte Carlo simulations to calculate the solvation enthalpies and statistical thermodynamics to account for zero-point vibrational and thermal contributions, the complexation energies for CP.HCl and CP.(HCl)2 are estimated from the experimental complexation enthalpies to be -17.4(14) and -34.0(20) kJ mol-1, while the value for CP.BF3 was derived to be -23.4(22) kJ mol-1. The experimental complexation energies are compared with the theoretical values derived from the MP2/6-31+G(d) potential energy surfaces and with single point energies calculated at the MP2/6-311++G(3df,2pd) level.
authors.affiliation: Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium.
authors.forename: W A
authors.initials: WA
authors.lastname: Herrebout
authors.forename: A
authors.initials: A
authors.lastname: Gatin
authors.forename: G P
authors.initials: GP
authors.lastname: Everaert
authors.forename: A I
authors.initials: AI
authors.lastname: Fishman
authors.forename: B J
authors.initials: BJ
authors.lastname: van der Veken
mesh_terms: D001128:Argon / Q000737:chemistry; D001880:Boranes / Q000737:chemistry*; D003080:Cold Temperature; D003517:Cyclopentanes / Q000737:chemistry*; D006358:Hot Temperature; D006851:Hydrochloric Acid / Q000737:chemistry*; D008968:Molecular Conformation; D009010:Monte Carlo Method; D013053:Spectrophotometry / Q000379:methods*; D013055:Spectrophotometry, Infrared; D013696:Temperature; D013816:Thermodynamics
chemical_list: D001880:Boranes; D003517:Cyclopentanes; D001128:Argon; C021274:boron trifluoride; D006851:Hydrochloric Acid