2-(2-Methyl-benzo-yl)benzoic acid: catemeric hydrogen bonding in a γ-keto acid.

The crystal structure of the title compound, C15H12O3, displays catemeric aggregation involving O-H⋯O hydrogen bonds progressing from the carboxyl group of one mol-ecule to the ketone O atom of another glide-related neighbor. The mol-ecule is twisted, with the toluene 80.61 (3)° out of plane with respect to the phenyl group of the benzoic acid.

3-Acetyl-benzoic acid.

In the crystal structure of the title compound, C(9)H(8)O(3), essentially planar mol-ecules [the carboxyl group makes a dihedral angle of 4.53 (7)° with the plane of the ring, while the acid group forms a dihedral angle of 3.45 (8)° to the ring] aggregate by centrosymmetric hydrogen-bond pairing of ordered carboxyl groups.

Improvements in complex mixture analysis by NMR: DQF-COSY iDOSY.

Diffusion-ordered NMR spectroscopy (DOSY NMR) is a highly useful tool for the study of complex mixtures via NMR. Often, spectral overlap limits the ability of obtaining cleanly separated subspectra of the components due to inherently instable multiexponential fits or data inversion procedures. Three-dimensional DOSY variants offer the advantage of separating individual peaks in an additional dimension, such that robust monoexponential fits to cross-peaks may be used to determine the diffusion coefficients with higher accuracy.

trans-4-Acetylcyclohexanecarboxylic acid and (+/-)-trans-2-acetylcyclohexanecarboxylic acid: hydrogen-bonding patterns in two isomeric keto acids.

Both title compounds, C(9)H(14)O(3), display carboxyl-dimer hydrogen-bonding patterns. The 4-acetyl isomer adopts a chiral conformation with negligible disordering of the methyl and carboxyl groups and forms centrosymmetric dimers across the b and c edges of the chosen cell [O.O = 2.

(+)-3,11-Dioxoandrost-4-ene-17 beta-carboxylic acid: catemeric hydrogen bonding in a steroidal keto acid.

The title keto acid, C(20)H(26)O(4), forms carboxyl-to-ketone hydrogen-bonding catemers [O...

1'-Acetylferrocene-1-carboxylic acid: an instance of hydrogen bonding in the rare dimeric acid-to-ketone mode.

The title compound, [Fe(C(6)H(5)O(2))(C(7)H(7)O)], adopts a conformation involving partial staggering of its rings and aggregates in the solid as acid-to-ketone hydrogen-bonding dimers [O.O = 2.720(4)A and O-H.