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On structural and spectroscopic differences between quinoline‐2‐carboxamides and their N ‐oxides in the solution and solid state
Author(s) -
Kamiński Radosław,
Schilf Wojciech,
Cmoch Piotr,
Dziembowska Teresa,
Woźniak Krzysztof
Publication year - 2009
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1533
Subject(s) - chemistry , quinoline , intramolecular force , hydrogen bond , intermolecular force , amide , molecule , chemical shift , carboxamide , crystallography , proton , medicinal chemistry , stereochemistry , organic chemistry , physics , quantum mechanics
Intramolecular hydrogen bonding in the primarily and secondarily substituted quinoline‐2‐carboxamides and their N ‐oxides has been studied in the solution by multinuclear NMR spectroscopy. Hydrogen bonding patterns and supramolecular arrangement in the solid state have been determined by single crystal X‐ray analysis. In quinoline‐2‐carboxamides weak, nonlinear intramolecular NH…N hydrogen bond is present, but in the solid state the intermolecular hydrogen bonds and packing forces are the factors that decide on the properties of 3D structures. In quinoline‐2‐carboxamide N ‐oxides the most important structural features are the intramolecular hydrogen bonds. Details of different weak interactions and resulting 3D arrangement of molecules are discussed. In the solution, two separate 1 H signals are observed for the primary quinoline‐2‐carboxamides in the range from ca . 5.8 to 8.1 ppm. The chemical shifts of the NH group's proton for studied R′‐quinoline‐2‐R‐carboxamides are in the range from 8.1 to 8.4 ppm. For the N ‐oxide of 4‐R′‐quinoline‐2‐carboxamides (R′ = H, Me, OPh, Cl and Br), the values of the proton chemical shifts of the NH group in the range from 10.78 to 11.38 ppm (for primary amides) indicating that this group forms hydrogen bonds with the oxygen of the N ‐oxide group. This bond is stronger than the NH…N bond in quinoline‐2‐carboxamides. For the secondary amide N ‐oxides, the δ (NH) values are increasing from 11.25 to 11.77 ppm in the sequence of substituents 4‐Br < 4‐Cl < 4‐H < 4‐Me < 4‐OPh. For 4‐substituted compounds these values depend also on the substituent effect. Copyright © 2009 John Wiley & Sons, Ltd.