The crystal structure of glutaric and pimelic acid. Alternation of properties in the series of dicarboxylic acids

Abstract

Glutaric acid and pimelic acid have analogous crystal structures. T h e CH, chains are stretched along the c-axis. the plane af the zigzag is nearly parallel to (100). Packing of the COOH groups is practically identical to that in adipic acid. This packing enforces a torsion in the molecules of the odd acids as a result of their axial symmetry. This torsion may well be the cause of the higher energy content of the +d dicarboxylic acids; an estimate of the torsion energy is made and is shown to be of the right order of magnitude.

Identification and Molecular Understanding of the Odd–Even Effect of Dicarboxylic Acids Aqueous Solubility

“…It was observed that the crystal structures were closely related to the chain length. Since then, several researchers began to study the crystalline nature of diacids: Macgillavry et al 29 explained 30 performed similar investigations on diacids, but without comparison between odd and even structures. In 1999, Boese et al 31 made a breakthrough to solve this problem by proposing a parallelogram-trapezoid model.…”

De-Pake-ing transform analysis of fully deuterated malonic acid

“…To the contrary, efficient packing requires that the carboxyl groups be twisted in the solid-state, leading to nonequivalent carboxyl rings on either side of the molecule [13]. Such an organization is observed in the crystal [12], but it is also expected in a powder to limited extent.…”

“…In the case of malonic acid, one might be tempted to assume that some averaging from the complicated motion associated with the acidic deuterons [13][14][15] would account for the reduced intensity of their de-Pake-ing signal and thus incorrectly report their QCCs. Instead, a proper interpretation requires consideration of the entire pattern, not just the main or most intense features.…”

Average increase in chain length of crystalline long chain compounds per carbon atom

“…The value of md9o can also be obtained from the c vs. n plot for monoclinic crystals. The only requirement is that the long chains be parallel or almost parallel to the c axis, as is known to be the case for the following monoclinic crystals: the C form of the n-alkanoic acids (26); the/3 form of the dicarboxylic acids (42), and the quarter-hydrates of the sodium-l-alkanesulfonates (53). If the chains are not exactly parallel to the c axis (or normal to the 001 planes), the resulting error in the value of dgo obtained from the linear equation for the c vs. n plot will be negligible for small angular differences.…”