On Comparing Crystal Growth Rates: Para Substituted Carboxylic Acids

Abstract

In this contribution the single crystal growth rates of four para substituted benzoic acids measured in toluene and isopropyl alcohol solutions are reported. Major objectives of the work have been to consider how such data might be correctly compared and how such comparisons may be related to underlying packing arrangements in the respective crystal structures. Morphological determinations formed an important part of the overall study. Consideration has been given to various practical issues arising from the varying solubility of the materials and growth rate dispersion among the measured crystal seeds. This provides suggestions as how best to measure growth rates for this purpose. The ultimate aims of such work have been to explore connections between growth and nucleation kinetics as well as to consider what such a data set might predict about the kinetics of other related molecules.

Mixed halobenzenes also prefer face⋯face approaches of aromatic rings, revealing a new inversion symthon

“…However, pairing with other inversion interactions gives aromatic stacks with a translation repeat of ∼7–8 Å between every second molecule. This feature occurs in OPAYUA, ISAWIK, REWFUV, UCEPAU and UCENOG01, and has also been discussed elsewhere 22 for p -toluic acid (PTOLIC01).…”

“…Similar investigations of the crystal structures of selected aromatic molecules that do not contain halogens will clarify the broader relevance of these symthons, and test the general methods deployed here to identify and characterise symthons. In a recent study 22 of para-substituted benzene carboxylic acids, the concept of symthons was extended to include close approaches to the centroids of carboxylic acid dimers. The pair of inversion interactions in p -toluic acid (PTOLIC01) are both symthon III, avoiding close contact between methyl groups.…”