Speciation of Substituted Benzoic Acids in Solution: Evaluation of Spectroscopic and Computational Methods for the Identification of Associates and Their Role in Crystallization

Self-association of four benzoic acid derivatives 2-chloro-4-nitrobenzoic acid, 2-methyl-4-nitrobenzoic acid, 3-hydroxybenzoic acid, and 2,6-dimethoxybenzoic acid in solution was investigated using spectroscopic measurements (Fourier transform infrared and 1H and 13C NMR spectroscopy) and molecular simulation methods. Based on the formation of hydrogen bonds, solvents can be divided into two groups: apolar solvents or solvents with a low hydrogen bond acceptor propensity, in which the benzoic acid derivatives form hydrogen-bonded dimers, and solvents with hydrogen bond acceptor propensity β > 0.3, interacting with the carboxylic group of benzoic acid, thus screening its interaction in the formation of self-associates. The formation propensity and structure of self-associates stabilized by weak interactions, such as π···π stacking and CH3···π interactions, however, are determined by the substituents in the benzene ring. Despite all the studied compounds being polymorphic, in none of the cases, an unequivocal structural link between self-associates present in the solution and the crystal form was observed

Investigating dietary life histories and mobility of children buried in St Gertrude Church Cemetery, Riga, Latvia (15th– 17th centuries AD)

Carbon and nitrogen isotope profiles were obtained from incremental dentine analysis of 19 non‐adults from a cemetery in Riga, Latvia. The research compared the life histories and diet between people buried in two mass graves and the general cemetery. The δ13C profiles of several children from the mass graves were similar but did not resemble the patterns seen in children from the general cemetery, suggesting that they probably represented a different population group. The rise in δ15N values towards the end of the life of four individuals from one mass grave suggests they were victims of an historically documented famine

The Effect of pH on Polymorph Formation of the Pharmaceutically Active Compound Tianeptine

The anti-depressant pharmaceutical tianeptine has been investigated to determine the dynamics of polymorph formation under various pH conditions. By varying the pH two crystalline polymorphs were isolated. The molecular and crystal structures have been determined to identify the two polymorphs. One polymorph is an amino carboxylic acid and the other polymorph is a zwitterion. In the solid state the tianeptine moieties are bonded through hydrogen bonds. The zwitterion was found to be less stable and transformed to the acid form. During this investigation an amorphous form was identified