Electronic spectra of organic molecules and their interpretation—V

Burawoy, A.; Critchley, J. P.

doi:10.1016/0040-4020(59)80025-9

Cited by 84 publications

(24 citation statements)

References 21 publications

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“…Other intermetallic catalysts were prepared in a similar way at 773, 873, or 1073 K of reduction temperature using a specific amount of the second metal precursor: Ga(NO 3 1), 1073 K. We carried out the reduction treatment at high temperature with SiO 2 support itself to investigate the effect of sintering of the support. N 2 adsorption experiments before and after the treatment (at 1073 and 873 K) revealed that only a slight sintering occurred at 1073 K (S BET : 673 → 622 m 2 ·g −1 ), whereas no sintering was observed at 873 K (S BET : 673 → 686 m 2 ·g −1 ).…”

Section: Methodsmentioning

confidence: 99%

Chemoselective Hydrogenation of Nitrostyrene to Aminostyrene over Pd- and Rh-Based Intermetallic Compounds

2014

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A noble catalytic system based on intermetallic compounds was developed for the chemoselective hydrogenation of p-nitrostyrene (NS) to p-aminostyrene (AS). The main concept of the catalyst design was to construct polar active sites consisting of two types of metals with different electronegativities. We prepared a series of Pd-and Rh-based intermetallics and investigated their catalytic properties in detail in the catalytic transfer hydrogenation of nitrobenzene and NS in the presence of 4-methyl-1-cyclohexene (MC) or methanol as a hydrogen donor. FT-IR studies of adsorbed CO confirmed that the number of Pd ensembles exposed on a surface was greatly decreased by the formation of an intermetallic phase; hence, the particle surface consisted of two metal elements being coadjacent at the atomic level. The product distribution achieved with Pd catalysts was dependent on the electronegativity of the second metal element: more electronegative metals gave higher AS selectivity and lower pethylnitrobenzene selectivity. Rh catalysts selectively gave AS, and their AS yields increased as the electronegativity of the second metal increased. The results revealed that an increase in the electronegativity of the second metal element provided polar sites and enhanced the activation of methanol as a hydrogen donor, which accelerated the hydrogenation of the nitro group of NS and, hence, improved the yield of AS. The high selectivity of Rh catalysts was due to the absence of MC activation ability, which caused the hydrogenation of the vinyl group of NS. Pd 13 Pb 9 exhibited the highest chemoselectivity toward AS (92%) among the investigated Pd catalysts. Moreover, RhPb 2 exhibited not only high AS selectivity (93%) but also the highest NS conversion (94%) among the investigated catalysts. RhPb 2 also exhibited high selectivity toward AS (91%), even when H 2 was used as a hydrogen source. Thus, intermetallics that contain Pb, which was the most electronegative metal used in this study, afforded good catalytic performance and were observed to be good catalysts for the chemoselective hydrogenation of NS.

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Section: Methodsmentioning

confidence: 99%

Chemoselective Hydrogenation of Nitrostyrene to Aminostyrene over Pd- and Rh-Based Intermetallic Compounds

2014

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“…The current industrial processes involve the use of stoichiometric amounts of reducing agents such as sodium hydrosulfide, iron, tin or zinc in ammonium hydroxide [3][4][5][6], catalysts based on PbPt/CaCO 3 with iron salts in solution [7], or Pt/C catalysts modified by H 3 PO 2 with soluble vanadium compounds as additives [1]. The discovery that gold nanoparticles supported on TiO 2 or Fe 2 O 3 catalyze the selective reduction of a nitro group in substituted nitroaromatics under mild reaction conditions [8] opened a way to substitute these environmentally non sustainable processes by others based on the use of easily recyclable solid catalysts and H 2 as reactant.…”

Section: Introductionmentioning

confidence: 99%

Tuning the Behavior of Au and Pt Catalysts for the Chemoselective Hydrogenation of Nitroaromatic Compounds

2011

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Efficient catalysts for the synthesis of functionalized anilines from the corresponding substituted nitroaromatics should combine an excellent chemoselectivity with a high hydrogenation activity. Attempts to increase the activity of the Au/TiO 2 catalyst and to improve the selectivity of traditional Pt catalysts, based on a previous understanding of the mode of action of supported gold and platinum nanoparticles, are reviewed and discussed.

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“…Selectivities up to 90% were obtained over gold for the selective hydrogenation of , -unsaturated carbonyl compounds to the corresponding unsaturated alcohols, which are important intermediates in the production of fine chemicals and pharmaceuticals (17,41,45-46,). Substituted aromatic amines, also important industrial intermediates, were selectively prepared from the corresponding nitro compounds with supported gold catalysts (47), whereas other catalytic systems exhibited major drawbacks such as by-product formation (55)(56)(57)(58)(59) and limited reusability (60). Hydrogenation reactions over gold have in common that the hydrogen molecule must be dissociated before it reacts.…”

Section: Introductionmentioning

confidence: 99%