These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: A structural systematic study of four isomers of difluoro-N-(3-pyridyl)benzamide.
    Author: McMahon J, Gallagher JF, Anderson FP, Lough AJ.
    Journal: Acta Crystallogr C; 2009 Jul; 65(Pt 7):o345-51. PubMed ID: 19578270.
    Abstract:
    The four isomers 2,4-, (I), 2,5-, (II), 3,4-, (III), and 3,5-difluoro-N-(3-pyridyl)benzamide, (IV), all with formula C(12)H(8)F(2)N(2)O, display molecular similarity, with interplanar angles between the C(6)/C(5)N rings ranging from 2.94 (11) degrees in (IV) to 4.48 (18) degrees in (I), although the amide group is twisted from either plane by 18.0 (2)-27.3 (3) degrees. Compounds (I) and (II) are isostructural but are not isomorphous. Intermolecular N-H...O=C interactions form one-dimensional C(4) chains along [010]. The only other significant interaction is C-H...F. The pyridyl (py) N atom does not participate in hydrogen bonding; the closest H...N(py) contact is 2.71 A in (I) and 2.69 A in (II). Packing of pairs of one-dimensional chains in a herring-bone fashion occurs via pi-stacking interactions. Compounds (III) and (IV) are essentially isomorphous (their a and b unit-cell lengths differ by 9%, due mainly to 3,4-F(2) and 3,5-F(2) substitution patterns in the arene ring) and are quasi-isostructural. In (III), benzene rotational disorder is present, with the meta F atom occupying both 3- and 5-F positions with site occupancies of 0.809 (4) and 0.191 (4), respectively. The N-H...N(py) intermolecular interactions dominate as C(5) chains in tandem with C-H...N(py) interactions. C-H...O=C interactions form R(2)(2)(8) rings about inversion centres, and there are pi-pi stacks about inversion centres, all combining to form a three-dimensional network. By contrast, (IV) has no strong hydrogen bonds; the N-H...N(py) interaction is 0.3 A longer than in (III). The carbonyl O atom participates only in weak interactions and is surrounded in a square-pyramidal contact geometry with two intramolecular and three intermolecular C-H...O=C interactions. Compounds (III) and (IV) are interesting examples of two isomers with similar unit-cell parameters and gross packing but which display quite different intermolecular interactions at the primary level due to subtle packing differences at the atom/group/ring level arising from differences in the peripheral ring-substitution patterns.
    [Abstract] [Full Text] [Related] [New Search]