Structural Elucidation of Enantiopure and Racemic 2-Bromo-3-Methylbutyric Acid

Seidel, Rüdiger W. and Nöthling, Nils and Goddard, Richard and Lehmann, Christian W. (2020) Structural Elucidation of Enantiopure and Racemic 2-Bromo-3-Methylbutyric Acid. Chemistry, 2 (3). pp. 691-699. ISSN 2624-8549

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Halogenated carboxylic acids have been important compounds in chemical synthesis and indispensable research tools in biochemical studies for decades. Nevertheless, the number of structurally characterized simple α-brominated monocarboxylic acids is still limited. We herein report the crystallization and structural elucidation of (R)- and rac-2-bromo-3-methylbutyric acid (2-bromo-3-methylbutanoic acid, 1) to shed light on intermolecular interactions, in particular hydrogen bonding motifs, packing modes and preferred conformations in the solid-state. The crystal structures of (R)- and rac-1 are revealed by X-ray crystallography. Both compounds crystallize in the triclinic crystal system with Z = 2; (R)-1 exhibits two crystallographically distinct molecules. In the crystal, (R)-1 forms homochiral O–H···O hydrogen-bonded carboxylic acid dimers with approximate non-crystallographic C2 symmetry. In contrast, rac-1 features centrosymmetric heterochiral dimers with the same carboxy syn···syn homosynthon. The crystal packing of centrosymmetric rac-1 is denser than that of its enantiopure counterpart (R)-1. The molecules in both crystal structures adopt a virtually identical staggered conformation, despite different crystal environments, which indicates a preferred molecular structure of 1. Intermolecular interactions apart from classical O–H···O hydrogen bonds do not appear to have a crucial bearing on the solid-state structures of (R)- and rac-

Item Type: Article
Subjects: Q Science > QD Chemistry
Depositing User: APLOS Library
Date Deposited: 11 Jul 2022 06:48
Last Modified: 11 Jul 2022 06:48

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