Gas-phase molecular structure of nicotinamide studied by electron diffraction combined with MP2 calculations

Tsuguhide Takeshima, Hiroshi Takeuchi, Toru Egawa, Shigehiro Konaka

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Abstract

The molecular structure of nicotinamide has been determined at 467 K by gas electron diffraction combined with MP2/ 6-31G** calculations. In the analysis of diffraction data, the potential function for torsion of the pyridine ring was assumed to be V(φ) = V1(1 - cos φ)/2 + V2(1 - cos 2φ)/2 + V4(1 - cos 4φ)/2, where φ denotes the torsional angle around the Cring-C(=0) bond. The following potential parameters (V/kJ mol-1) and structural parameters of (E)-nicotinamide (rg/Å and ∠αo) have been obtained: V1 = 5-7+10, V2 = 11.5 (assumed), V4 = -9(4), 〈r(Cring-Cring)〉 = 1.403(4), 〈r(Nring-Cring)〉 = 1.328(6), r(Cring-C(=O)) = 1.498(8), r(C=O) = 1.216(5), r((O=)C-N) = 1.362(12), ∠CringNringCring = 117.5(2), 〈∠CringCringCring〉 = 118.0 (dependent parameter), 〈∠NringCringCring〉 = 124.3 (dependent parameter), ∠CringCO = 121.9(6), ∠Cring- C(=O)N = 115.0 (dependent parameter), ∠CcisCC(=O) = 120.5(17), where Ccis denotes the ring carbon atom at the cis position against the nitrogen atom of the NH2 group. Parenthesized numbers denote the estimated limits of error and the angle bracket denotes average values. These structural parameters are close to the corresponding parameters of pyridine and acetamide except for r(Nring-Cring) and ∠CringNringCring. The Nring-Cring and C=O bonds are shorter than the corresponding parameters in the crystal by 0.01 Å and the (O=)C-N bond is longer than that in the crystal by 0.03 Å. These differences are ascribed to the effect of intermolecular hydrogen bonding on the structure in the crystal.

Original languageEnglish (US)
Pages (from-to)197-205
Number of pages9
JournalJournal of Molecular Structure
Volume644
Issue number1-3
DOIs
StatePublished - Jan 1 2003

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Keywords

  • Ab initio calculations
  • Gas electron diffraction
  • Hydrogen bonding
  • Molecular structure
  • Nicotinamide

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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