(±)-3-Oxocyclopentanecarboxylic acid: the smallest keto acid known to aggregate by catemeric hydrogen bonding

Abstract

The title compound, C6H8O3, is the smallest keto acid yet found to aggregate in the solid as acid-to-ketone hydrogen-bonded catemers. Four translational chains pass through the cell in the a direction [O...O = 2.6915 (14) A and O-H...O = 166 degrees]. Two intermolecular C-H...O close contacts exist, involving both carbonyl functions.

6-Chloronicotinic acid

“…2). This pattern can be designated as an acid-topyridine catemer motif, similar to the acid-to-keto catemer reported for other compounds with the carboxylic acid functional group present (Malak et al, 2006). Since the pyridine N atom acts as the hydrogen-bond acceptor, the other hydrogenbond acceptor of the molecule, C O of the carboxylic acid group, is not involved in any hydrogen bonding.…”

Three closely related dibenzazepine carboxylic acids: hydrogen-bonded aggregation in one, two and three dimensions

“…Thus, -keto acids form C (7) chains (e.g. Thompson et al, 2004;Malak et al, 2006), -keto acids form C(8) chains (e.g. Davison, Kikolski et al, 2004) and "-keto acids form C (9) chains (e.g.…”

(±)-2-Oxocyclopentaneacetic acid: catemeric hydrogen bonding in a γ-keto acid

“…The conformational flexibility associated with cyclopentane rings is a solution characteristic; in the crystal, the requirements disfavoring hydrogen eclipsing and favoring pseudo-equatorial substituents leaves a system like (I) with few actual conformational options. As a result (I) joins a number of nominally flexible cyclic molecules we have found that behave much more like rigid systems and adopt catemeric H-bonding modes (Barcon et al, 2002;Malak et al, 2006;Lalancette & Thompson, 2003).…”

“…An issue of interest is the minimum requirements for catemer formation. However, the very smallest molecules offer several experimental problems (volatility, low crystallinity, little structural variability), so that few C 3 -C 6 keto-acids have been previously reported (Harata et al, 1977;Malak et al, 2006;Efthimiopoulos et al, 2009). We now report the crystal structure of the title C 7 γ-keto acid (I), among the smallest found to aggregate in the solid as a catemer.…”

“…For background to catemers and hydrogen bonds, see: Barcon et al (1998Barcon et al ( , 2002; Coté et al (1996); DeVita Dufort et al (2007); Efthimiopoulos et al (2009); Harata et al (1977); Lalancette & Thompson (2003); Lalancette et al (2006); Malak et al (2006); Newman et al (2002); Steiner (1997); Stork et al (1963).…”