Livius Cotarca

Principal component analysis of data on the catalytic oxidation of toluene

Abstract The simultaneous production of benzoic acid and benzaldehyde by liquid phase oxidation of toluene in the presence of Co(acetate) 2 catalyst was investigated. Principal component analysis (PCA) was applied to evaluate the data. The analysis identified two main groupings according to which the most significant technological parameters could be identified. Furthermore, the conversion related to the maximal concentration of benzaldehyde correlates with the principal component responsible for the greatest variance. Results of the PCA indicated that, with increasing conversion, the reaction route leading to byproducts is gaining importance compared to that yielding benzoic acid. Simultaneously, it became possible to trace the experimental errors and to evaluate the robustness of the method.

Preparation and Mechanism of Solvolysis ofN-Hydroxy-α-oxobenzeneethanimidoyl Chloride, a 2-(Hydroxyimino)-1-phenylethan-1-one Derivative: Molecular Structure ofα-Oxo-oximes (=α-(Hydroxyimino) Ketones)

Acid-catalyzed methanolysis of N-hydroxy-α-oxobenzeneethanimidoyl chloride (1), a 2-(hydroxyimino)-1-phenylethan-1-one derivative obtained in one step from acetophenone, leads to a constant ratio of methyl α-oxobenzeneacetate (2) and methyl α-(hydroxyimino)benzeneacetate (3). 13C(α) Labelled [13C]-1 affords 13C(α) labelled [13C]-3, thus discarding the hypothesis of its formation via 1,2-arene migration. The reported sequence opens a novel approach to phenylglyoxylic and mandelic acid esters (=α-oxobenzeneacetic and α-hydroxybenzeneacetic acid esters), from acetophenone. The molecular structures of 1 and 3 were determined by X-ray structure analysis and compared with previously reported crystallographic data of α-oxo-oximes (=α-(hydroxyimino) ketones) 4 and 6u2009–u20098. The unique stereoelectronic characteristics of the α-oxo-oxime moiety are discussed. All α-oxo-oximes share the following structural characteristics: (E)-configuration of the oxime C=N−OH bond (i.e. OH and C=O trans), the s-trans conformation of the oxo and imino moieties about the C(α)-C(=NOH) single bond, and intermolecular H-bonding. They differ from the isostructural β-diketone enols by the absence of resonance-assisted intramolecular H-bonding.

Long-distance control in stereoselective reduction of 3-[3-(4′-bromo[1,1′-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one: Relative configuration of prevailing diastereomer and absolute configuration of its enantiomers

Depending on the reducing agent and reaction conditions, diastereoselective reduction of 3-[3-(4′-bromo[1,1′-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one (2) proceeds with different stereoselectivity; a surprisingly high, approximately 90% d.e. of 4A is achieved with NaBH4 in MeOH at low temperature. Resulting diastereomeric racemates 4A and 4B are separated and their respective syn and anti configurations are assigned on the bases of mechanic considerations, supported by the 1H-NMR spectra and conformational analysis based on MM2 calculations. The syn diastereomer 7A, 4-OMe derivative of 4A, was partially resolved by acylation at C(3)-OH with S-(−)-camphanic acid to camphanyl ester 12 of (−)-7A, leaving (+)-enantiomer 7A. The assignment of absolute 1R,3S-configuration to (−)-7A is based on comparison of its CD spectrum with those of the model compounds S-14 and R-15, which represent partial chromophores 4-hydroxy-2H-1-benzopyran-2-one (4-hydroxycoumarin) A, and 4′-bromo-1,1′-biphenyl B; their exciton coupling in (−)-7A is suggested. Chirality 9:512–522, 1997.

Oxidative decarboxylation of cyclohexane monocarboxylic acid III. Initiated oxidation

A mechanism is suggested for the oxidative decarboxylation of cyclohexane monocarboxylic acid initiated by decomposition of H2O2. The process is a non-branching chain reaction. Cyclohexanone and cyclohexanol form in termination reactions.