Article

A Theoretical Study of Intermolecular Interaction and Hydrogen Bond for Furan with HCl and CH<SUB>4- n </SUB>Cl<SUB> n </SUB> ( n = 0-3)

Internet Electronic Journal of Molecular Design 01/2003;
Source: DOAJ

ABSTRACT Furan has both the oxygen lone pair electrons and an aromatic π-electron. The study of the interaction between furan as a proton acceptor and a proton donor is important to understand the properties of furan and the related hydrogen bond. The geometries, intermolecular energies and vibrational properties of the furan-HCl and furan-CH4- n Cl n ( n = 0-3) complexes have been performed using the second order Moller-Plesset perturbation theory. The NBO analysis of the optimized geometries has also been performed. The optimized geometries of furan-HCl and furan-CH4- n Cl n ( n = 0-3) show both the C(Cl)-H...O and C(Cl)-H...π interactions. In all of the optimized geometries of furan-CH4- n Cl n ( n = 0-3), C-H bond lengths are shorten and vibrational frequencies are blue-shifted, while for the furan-HCl complex, C-H bond length is lengthened and vibrational frequencies are red-shifted. The NBO analysis shows that, for the furan-CH4- n Cl n ( n = 0-3) complexes, the charge transfer from the lone pairs of the O atom to both σ*(CH) antibonding MO and lone pairs of Cl atom, which is the important feature for blue-shifted hydrogen bond. Both lone pairs and π electrons of furan can be acted as a proton acceptor interacting with a proton donor. Cl-H...O(π) is a conventional hydrogen bond , while C-H...O(π) is a blue-shifted hydrogen bond.

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    ABSTRACT: The structures and binding energies of a series of C−H···X hydrogen-bonded complexes involving acetylene, ethylene, and ethane as proton donors and the first- and second-row hydrides CH4, NH3, OH2, FH, PH3, SH2, and ClH as proton acceptors have been determined. Geometries were optimized with both the MP2 and the B3-LYP methods in conjuction with the 6-311+G(3df,2p) basis set. In general, we note good agreement between MP2 and B3-LYP hydrogen-bonded structures. However, for some very weakly bound complexes larger differences exist, particularly in the r(H···X) distance, and in these instances the MP2 results are determined (from comparative CCSD(T) calculations) to be more reliable. The CCSD(T)/6-311+G(3df,2p) binding energies (De), which include corrections for basis set superposition errors, are very similar for the MP2 and B3-LYP geometries, reflecting the relative insensitivity of De to geometry for weakly bound complexes. The C−H···X hydrogen-bond strength (D0) shows a considerable dependence on the acidity of the C−H donor group and on the nature of the proton-accepting group. The strongest hydrogen bonds are formed between acetylene and either NH3 (9.2 kJ mol-1) or OH2 (7.7 kJ mol-1). These values decrease significantly for the corresponding complexes between acetylene and FH, CH4 or the second-row hydrides. The binding energies for the complexes between ethylene and either NH3 or OH2 (2.1 and 1.5 kJ mol-1, respectively) are much smaller than those of the corresponding acetylene complexes. The complexes between ethylene and PH3, SH2 or ClH, as well as the complexes between ethane and NH3 or H2O, are more weakly bound again and have binding energies less than 1.0 kJ mol-1.
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