Title:Distinguishment of Weak Interactions of Hydrogen Atoms Bound to Carbon
Atoms: X-Ray Crystal Structural and Hirshfeld Surface Analyses of 2-
Hydroxy-7-methoxy-3-(2,4,6-trimethylbenzoyl)naphthalene with the 2-
Methoxylated Homologue
Volume: 19
Issue: 9
Author(s): Kikuko Iida, Toyokazu Muto, Miyuki Kobayashi, Hiroaki Iitsuka, Kun Li, Noriyuki Yonezawa*Akiko Okamoto*
Affiliation:
- Department of Organic and Polymer Materials Chemistry, Tokyo University of Agriculture and Technology, 2-24-16,
Nakamachi, Koganei, Tokyo 184-8588, Japan
- Japan Association for Working Environment Measurement, 6th floor,
Mita Roudou Kijun Kyoukai Bldg, 4-4-5, Shiba, Minato-ku, Tokyo 108-0014, Japan
- Department of Organic and Polymer Materials Chemistry, Tokyo University of Agriculture and Technology, 2-24-16,
Nakamachi, Koganei, Tokyo 184-8588, Japan
Keywords:
Non-coplanarly accumulated aromatic rings, weak interactions, Hirshfeld surface analysis, classical hydrogen bonds, nonclassical hydrogen bonds, H…H interactions.
Abstract: X-ray crystal and Hirshfeld surface analyses of 2-hydroxy-7-methoxy-3-(2,4,6-
trimethylbenzoyl)naphthalene and its 2-methoxylated homologue show quantitatively and visually
distinct molecular contacts in crystals and minute differences in the weak intermolecular interactions.
The title compound has a helical tubular packing, where molecules are piled in a two-folded
head-to-tail fashion. The homologue has a tight zigzag molecular string lined up behind each other
via nonclassical intermolecular hydrogen bonds between the carbonyl oxygen atom and the hydrogen
atom of the naphthalene ring. The dnorm index obtained from the Hirshfeld surface analysis
quantitatively demonstrates stronger molecular contacts in the homologue, an ethereal compound,
than in the title compound, an alcohol, which is consistent with the higher melting temperature of
the former than the latter. Stabilization through the significantly weak intermolecular nonclassical
hydrogen bonding interactions in the homologue surpasses the stability imparted by the intramolecular
C=O…H–O classical hydrogen bonds in the title compound. The classical hydrogen bond
places the six-membered ring in the concave of the title molecule. The hydroxy group opposingly
disturbs the molecular aggregation of the title compound, as demonstrated by the distorted H…H
interactions covering the molecular surface, owing to the rigid molecular conformation. The position
of effective interactions predominate over the strength of the classical/nonclassical hydrogen
bonds in the two compounds.