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Structures and energetic properties of 4‐halobenzamides
Author(s) -
Piontek Aleksandra,
Bisz Elwira,
Dziuk Błażej,
Szostak Roman,
Szostak Michal
Publication year - 2018
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229618013463
Subject(s) - amide , chemistry , morpholine , planarity testing , resonance (particle physics) , crystallography , halogen , ring (chemistry) , stereochemistry , molecular geometry , computational chemistry , molecule , medicinal chemistry , organic chemistry , physics , alkyl , particle physics
The amide bond represents one of the most fundamental functional groups in chemistry. The properties of amides are defined by amidic resonance (n N →π* C=O conjugation), which enforces planarity of the six atoms comprising the amide bond. Despite the importance of 4‐halo‐substituted benzamides in organic synthesis, molecular interactions and medicinal chemistry, the effect of 4‐halo‐substitution on the properties of the amide bond in N , N ‐disubstituted benzamides has not been studied. Herein, we report the crystal structures and energetic properties of a full series of 4‐halobenzamides. The structures of four 4‐halobenzamides (halo = iodo, bromo, chloro and fluoro) in the N ‐morpholinyl series have been determined, namely 4‐[(4‐halophenyl)carbonyl]morpholine, C 11 H 12 X NO 2 , for halo = iodo ( X = I), bromo ( X = Br), chloro ( X = Cl) and fluoro ( X = F). Computations have been used to determine the effect of halogen substitution on the structures and resonance energies. 4‐Iodo‐ N ‐morpholinylbenzamide crystallized with a significant distortion of the amide bond (τ + χ N = 33°). The present study supports the correlation between the Ar—C(O) axis twist angle and the twist angle of the amide N—C(O) bond. Comparison of resonance energies in synthetically valuable N ‐morpholinyl and N ‐piperidinyl amides demonstrates that the O atom of the morpholinyl ring has a negligible effect on amidic resonance in the series.