An experimental charge density study of aliphatic dicarboxylic acids

By employing reliable structural data on malonic, succinic, glutaric, adipic and pimelic acids, obtained by a single crystal X-ray crystallographic study of these systems (using a CCD detector), the total electron densities and the Laplacians at the critical points of various bonds including the dimeric hydrogen bonds have been obtained. The study shows interesting systematics in the charge densities and Laplacians in the series of dicarboxylic acids. Malonic and pimelic acids exhibit minimum charge density in the C–C, C–O and the O–H bonds while glutaric acid shows the maximum density. The CO and the C–H bonds exhibit the opposite trend. The C–O and the CO bonds in malonic and glutaric acids have unusual Laplacians. The estimated dipole moment in the solid state shows alternation, but there is no alternation in any of the structural parameters. The present study also indicates the role of interchain interactions.