Structure determination of methyl nicotinate and methyl picolinate by gas electron diffraction combined with ab initio calculations

Hajime Kiyono, Ryosuke Tatsunami, Teruyo Kurai, Hiroshi Takeuchi, Toru Egawa, Shigehiro Konaka

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Abstract

The molecular structures of isomers, methyl nicotinate and methyl picolinate, have been studied by gas electron diffraction. The samples were heated to 341-343 K by using a high-temperature nozzle to get enough vapor pressure. HF/6-31G* ab initio calculations were carried out, and structural constraints were taken from their results. Vibrational amplitudes and shrinkage corrections were calculated from the harmonic force constants given by normal coordinate analyses. The principal structural parameters of the s-trans conformer of methyl nicotinate are as follows (angle brackets mean averaged values): 〈rg(N-C)〉 = 1.337(7) Å; 〈rg(C-C)ring〉 = 1.402(3) Å; rg(Cring-C(=O)) = 1.480(12) Å; rg(C=O) = 1.199(7) Å; 〈rg(C-O)〉 = 1.380(11) Å; ∠αCNC = 119.0(14)°; 〈∠αNCC) = 122.8(11)°; ∠α(N=)C-Cring-C(=O) = 118.3(12)°; ∠αCring-C=O = 121.5(12)°; ∠αCring-C-O = 115.6(10)°. Those of the s-trans conformer of methyl picolinate are as follows: 〈rg(N-C)〉 = 1.344(7) Å; 〈rg(C-C)ring〉 = 1.398(4) Å; rg(Cring-C(=O)) = 1.497(11) Å; rg(C=O) = 1.209(7) Å; 〈rg(C-O)〉 = 1.380(11) Å; ∠αCNC = 117.2(12)°; 〈∠αNCC〉 = 123.9(12)°; ∠αN-C-C(=O) = 115.1(10)°; ∠αCring-C=O = 121.0(12)°; ∠αCring-C-O = 115.1(12)°. The structural parameters of the two isomers and methyl isonicotinate have been compared and their similarity and differences have been discussed.

Original languageEnglish
Pages (from-to)1405-1411
Number of pages7
JournalJournal of Physical Chemistry A
Volume102
Issue number8
DOIs
Publication statusPublished - 1998 Feb 19

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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