Theoretical study of substituent effects on the geometry and strain enthalpy in [2,2]paracyclophanes
Department of Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, Bratislava, SK-81237 Slovakia
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Abstract: The substituent effect on the geometry and strain enthalpy of [2,2]paracyclophane is theoretically investigated by density functional theory. Gas-phase calculations were performed for twenty distinct electron donating and electron withdrawing substituents. The largest out-of-plane distortion of phenyl rings is exhibited by —SCN and —CF3 groups. On the other hand, —OH, —CH3 and —F groups show the minimal deformation. The strain enthalpy for unsubstituted [2,2]paracyclophane associated with repulsive forces between phenyl units reached up to 118.5 kJ mol–1. Any substitution causes increase of the strain enthalpy value proportionally to the absolute values of Hammett para-substituent constants. Two separate linear dependences with similar slopes were obtained for monosubstituted as well as double symmetrically substituted derivatives.
Keywords: Paracyclophane, B3LYP-D3 study, intermolecular forces, aromaticity, strain enthalpy, Hammett constants
Full paper in Portable Document Format: acs_0233.pdf
Acta Chimica Slovaca, Vol. 9, No. 1, 2016, pp. 6—13, DOI: 10.1515/acs-2016-0002