, Volume 43, Issue 1, pp 51-57
Date: 17 Nov 2012

Unusual C–H···π Interactions in the Structure of 3,4,5-Trimethoxy-N-p-tolylbenzamide

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Abstract

3,4,5-trimethoxy-N-p-tolylbenzamide, C17H19NO4, (1), is a benzanilide derivative derived from p-toluidine and 3,4,5-trimethoxybenzoyl chloride. The structure was identified from spectroscopic and elemental analysis data and unambiguously confirmed by the single crystal X-ray diffraction studies in space group P21, with a = 5.1065(7) Å; b = 13.9148(18) Å; c = 11.2054(14) Å; β = 103.118(7)°; Z = 2. In the X-ray structure packing is predictably influenced by strong N–H···O hydrogen bonds, augmented by C–H···O contacts generating R 1 2 (6) ring motifs and forming chains of molecules along the b axis. Chains are also linked in a head-to-tail fashion by an additional weak Ar–C–H···O contact involving the tolyl methyl group. A particularly unusual feature of the packing in this structure however, is the extensive contribution of C–H···π interactions, involving two hydrogen atoms from each of the methyl groups of the 3- and 5-methoxy substituents. These link the chains into a three-dimensional network. A CSD investigation of intermolecular interactions involving both phenyl-bound and methoxy methyl groups is also presented.

Graphical Abstract

The structure of 3,4,5-trimethoxy-N-p-tolylbenzamide is notable for the occurrence of C–H···π interactions involving two hydrogen atoms from each of the 3- and 5-methoxy groups.