Molecular orbital studies of the nitromethane-ammonia complex. An unusually strong C-H⋯N hydrogen bond

L. Túri, J. J. Dannenberg

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45 Citations (Scopus)

Abstract

Ab initio molecular orbital calculations using various basis sets up to D95++(d,p) with full geometry optimization at the second order Møller-Plesset (MP2) level have been performed on several possible geometries of the 1:1 complex of nitromethane and ammonia. The complex is stabilized by 6.38 kcal/mol at MP2/D95++(d,p). After application of the counterpoise correction (CP) for the basis set superposition error (BSSE), the stabilization becomes 4.40 kcal/mol. Corrections for zero-point vibrational energy (ZPVE) and other vibrational corrections lower the stabilization by 1.38 to give a stabilization enthalpy of 3.02 kcal/mol. As the combination of CP and ZPVE is known to overcorrect, the interaction energy should be somewhat greater than this value. The preferred geometry involves a C-H⋯N and two N-H⋯O interactions. The CH⋯N interaction can be characterized as an H bond, while the N-H⋯O interactions seem more characteristic of electrostatic interactions. Rotation of the nitromethane to break the N-H⋯O interactions lowers the stabilization energy by only 0.99 kcal/mol before consideration of ZPVE (which would increase the relative stabilization of this rotated structure). Two other likely geometries, such as that optimizing the individual H bonds between the each of nitro oxygens and two of the ammonia H's, or that with a three center O⋯H⋯O bond between the nitro and the ammonia, are shown to be less stable. The former is predicted to be a transition state. Semiempirical calculations were performed for comparison. While the AM1 results agree with the ab initio calculations, the PM3 and SAM1 results do not.

Original languageEnglish
Pages (from-to)639-641
Number of pages3
JournalJournal of Physical Chemistry
Volume99
Issue number2
Publication statusPublished - 1995

Fingerprint

nitromethane
Molecular orbitals
Ammonia
ammonia
molecular orbitals
Hydrogen bonds
Stabilization
hydrogen bonds
stabilization
Geometry
interactions
geometry
Orbital calculations
energy
Coulomb interactions
Enthalpy
Oxygen
enthalpy
electrostatics
optimization

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

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title = "Molecular orbital studies of the nitromethane-ammonia complex. An unusually strong C-H⋯N hydrogen bond",
abstract = "Ab initio molecular orbital calculations using various basis sets up to D95++(d,p) with full geometry optimization at the second order M{\o}ller-Plesset (MP2) level have been performed on several possible geometries of the 1:1 complex of nitromethane and ammonia. The complex is stabilized by 6.38 kcal/mol at MP2/D95++(d,p). After application of the counterpoise correction (CP) for the basis set superposition error (BSSE), the stabilization becomes 4.40 kcal/mol. Corrections for zero-point vibrational energy (ZPVE) and other vibrational corrections lower the stabilization by 1.38 to give a stabilization enthalpy of 3.02 kcal/mol. As the combination of CP and ZPVE is known to overcorrect, the interaction energy should be somewhat greater than this value. The preferred geometry involves a C-H⋯N and two N-H⋯O interactions. The CH⋯N interaction can be characterized as an H bond, while the N-H⋯O interactions seem more characteristic of electrostatic interactions. Rotation of the nitromethane to break the N-H⋯O interactions lowers the stabilization energy by only 0.99 kcal/mol before consideration of ZPVE (which would increase the relative stabilization of this rotated structure). Two other likely geometries, such as that optimizing the individual H bonds between the each of nitro oxygens and two of the ammonia H's, or that with a three center O⋯H⋯O bond between the nitro and the ammonia, are shown to be less stable. The former is predicted to be a transition state. Semiempirical calculations were performed for comparison. While the AM1 results agree with the ab initio calculations, the PM3 and SAM1 results do not.",
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AU - Dannenberg, J. J.

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N2 - Ab initio molecular orbital calculations using various basis sets up to D95++(d,p) with full geometry optimization at the second order Møller-Plesset (MP2) level have been performed on several possible geometries of the 1:1 complex of nitromethane and ammonia. The complex is stabilized by 6.38 kcal/mol at MP2/D95++(d,p). After application of the counterpoise correction (CP) for the basis set superposition error (BSSE), the stabilization becomes 4.40 kcal/mol. Corrections for zero-point vibrational energy (ZPVE) and other vibrational corrections lower the stabilization by 1.38 to give a stabilization enthalpy of 3.02 kcal/mol. As the combination of CP and ZPVE is known to overcorrect, the interaction energy should be somewhat greater than this value. The preferred geometry involves a C-H⋯N and two N-H⋯O interactions. The CH⋯N interaction can be characterized as an H bond, while the N-H⋯O interactions seem more characteristic of electrostatic interactions. Rotation of the nitromethane to break the N-H⋯O interactions lowers the stabilization energy by only 0.99 kcal/mol before consideration of ZPVE (which would increase the relative stabilization of this rotated structure). Two other likely geometries, such as that optimizing the individual H bonds between the each of nitro oxygens and two of the ammonia H's, or that with a three center O⋯H⋯O bond between the nitro and the ammonia, are shown to be less stable. The former is predicted to be a transition state. Semiempirical calculations were performed for comparison. While the AM1 results agree with the ab initio calculations, the PM3 and SAM1 results do not.

AB - Ab initio molecular orbital calculations using various basis sets up to D95++(d,p) with full geometry optimization at the second order Møller-Plesset (MP2) level have been performed on several possible geometries of the 1:1 complex of nitromethane and ammonia. The complex is stabilized by 6.38 kcal/mol at MP2/D95++(d,p). After application of the counterpoise correction (CP) for the basis set superposition error (BSSE), the stabilization becomes 4.40 kcal/mol. Corrections for zero-point vibrational energy (ZPVE) and other vibrational corrections lower the stabilization by 1.38 to give a stabilization enthalpy of 3.02 kcal/mol. As the combination of CP and ZPVE is known to overcorrect, the interaction energy should be somewhat greater than this value. The preferred geometry involves a C-H⋯N and two N-H⋯O interactions. The CH⋯N interaction can be characterized as an H bond, while the N-H⋯O interactions seem more characteristic of electrostatic interactions. Rotation of the nitromethane to break the N-H⋯O interactions lowers the stabilization energy by only 0.99 kcal/mol before consideration of ZPVE (which would increase the relative stabilization of this rotated structure). Two other likely geometries, such as that optimizing the individual H bonds between the each of nitro oxygens and two of the ammonia H's, or that with a three center O⋯H⋯O bond between the nitro and the ammonia, are shown to be less stable. The former is predicted to be a transition state. Semiempirical calculations were performed for comparison. While the AM1 results agree with the ab initio calculations, the PM3 and SAM1 results do not.

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