The catalytic effects of various third molecules on reaction channels of weakly bound complex CO 2⋯HF systems in the vapor phase

Abstract

In this investigation, reaction channels of weakly bound complexes CO 2⋯HF, CO 2⋯HF⋯H 2O, CO 2⋯HF⋯NH 3, CO 2⋯HF⋯CH 3OH, CO 2⋯HF⋯NH 2CH 3, CO 2⋯HF⋯NH(CH 3) 2 and CO 2⋯HF⋯N(CH 3) 3 systems were studied at the B3LYP/6-311++G(3df,2pd) level. The conformers of syn-fluoroformic acid or syn-fluoroformic acid plus a third molecule (H 2O, NH 3, CH 3OH, NH 2CH 3, NH(CH 3) 2 or N(CH 3) 3) were found to be more stable than the conformers of the related anti-fluoroformic acid or anti-fluoroformic acid plus a third molecule (H 2O, NH 3, CH 3OH, NH 2CH 3, NH(CH 3) 2 or N(CH 3) 3). However, the weakly bound complexes were found to be more stable than either the related syn- and anti- type fluoroformic acid or the acid plus third molecule (H 2O, NH 3, CH 3OH, NH 2CH 3, NH(CH 3) 2 or N(CH 3) 3) conformers. They decomposed into CO 2+HF, CO 2+H 3OF, CO 2+NH 4F, CO 2+(CH 3)OH 2F, CO 2+NH 3(CH 3)F, CO 2+NH 2(CH 3) 2F, or CO 2+NH(CH 3) 3F combined molecular systems. The weakly bound complexes have seven reaction channels, each of which includes weakly bound complexes and their related systems. Moreover, each reaction channel includes two transition state structures. The transition state between the weakly bound complex and anti-fluoroformic acid type structure (T 13) is significantly higher than that of internal rotation (T 23) between the syn- and anti-FCO 2H (or FCO 2H⋯H 2O, FCO 2H⋯NH 3, FCO 2H⋯CH 3OH, FCO 2H⋯NH 2CH 3, FCO 2H⋯NH(CH 3) 2, or FCO 2H⋯N(CH 3) 3) structures. However, adding the third molecule H 2O, NH 3, CH 3OH, NH 2CH 3, NH(CH 3) 2 or N(CH 3) 3 can significantly reduce the activation energy of T 13. The catalytic strengths of the third molecules are predicted to follow the order H 2O<NH 3<CH 3OH<.NH 2CH 3<NH(CH 3) 2<N(CH 3) 3.