LOCAL ORDERS IN SIMPLE AND ASSOCIATED LIQUIDS

AS STUDIED BY X-RAY SCATTERING

S. Trabelsi, S. Nasr*

Laboratoire de Physico-Chimie des Matériaux, Faculté des Sciences, 5000 Monastir, Tunisie

* Corresponding author. E-mail address: salah_nasr1@yahoo.fr

Received : 30 November 2002 ; revised version accepted : 22 October 2003

Abstract

The structures of acetamide (AM) (CH3CONH2) and N, N-dimethylacetamide (DMA) (CH3CON(CH3)2) are respectively determined at 346 K and 298 K, by means of X-ray diffraction using a ?-2? diffractometer. Experimental data are analyzed to yield the structure factors SM (q) and the distinct pair correlation functions gL(r). Intramolecular parameters within a (DMA) molecule are determined. The pair correlation function of liquid (DMA) shows that the intermolecular arrangement is practically fully disordered and no evidence for the cluster formation of molecules has been found. Whereas, the hydrogen bond network in the liquid (AM) leads to some structural units similar to the ones existing in the two crystalline forms. The comparison between the distinct structure factors DM(q) and the pair correlation functions g( r ) of the two liquids shows the role of the hydrogen bonding in the associated liquids.

Keywords: N, N-dimethylacetamide; Acetamide; Hydrogen bond; Local arrangement; X-ray scattering.

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