15892-23-6Relevant academic research and scientific papers
How to modulate catalytic properties in nanosystems: The case of iron-ruthenium nanoparticles
Kelsen, Vinciane,Meffre, Anca,Fazzini, Pier-Francesco,Lecante, Pierre,Chaudret, Bruno
, p. 1714 - 1720 (2014)
Ultrasmall FeRu bimetallic nanoparticles were prepared by co-decomposition of two organometallic precursors, {Fe[N(Si(CH3)3) 2]2}2 and (η4-1,5- cyclooctadiene)(η6-1,3,5-cyclooctatriene)ruthenium(0) (Ru(COD)(COT)), under dihydrogen at 150 °C in mesitylene. A series of FeRu nanoparticles of sizes of approximately 1.8 nm and incorporating different ratios of iron to ruthenium were synthesized by varying the quantity of the ruthenium complex introduced (Fe/Ru=1:1, 1:0.5, 1:0.2, and 1:0.1). FeRu nanoparticles were characterized by TEM, high-resolution TEM, and wide-angle X-ray scattering analyses. Their surface was studied by hydride titration and IR spectroscopy after CO adsorption and their magnetic properties were analyzed by using a superconducting quantum interference device (SQUID). The FeRu nanoparticles were used as catalysts in the hydrogenation of styrene and 2-butanone. The results indicate that the selectivity of the nanoparticle catalysts can be modulated according to their composition and therefore represent a case study on fine-tuning the reactivity of nanocatalysts and adjusting their selectivity in a given reaction. Singing a bimetallic tune: The selectivity of FeRu nanocatalysts in hydrogenation reactions can be tuned by adjusting the Ru content in bimetallic FeRu ultrasmall nanoparticles.
Controlling surface crowding on a Pd catalyst with thiolate self-assembled monolayers
Schoenbaum, Carolyn A.,Schwartz, Daniel K.,Medlin, J. Will
, p. 92 - 99 (2013)
The relationship between surface crowding and catalytic activity was investigated using thiolate self-assembled monolayers (SAMs) on Pd/Al 2O3 catalysts. The surface density of the thiolate modifier was controlled by varying the steric bulk of the organic substituent. A straight-chain alkanethiol 1-octadecanethiol (C18), with a nearest-neighbor spacing of ～4.7 A on Pd(1 1 1) surfaces, created a denser SAM coating than 1-adamantanethiol (AT) with a nearest-neighbor spacing of ～6.4 A. Diffuse reflectance infrared spectroscopy revealed that CO adsorbate molecules adsorbed only on threefold hollow and atop sites on C18-modified surfaces. On AT-modified surfaces, however, access to bridging and additional linear sites was also observed. Analysis of adsorption isotherms suggested that CO adsorption energies were comparable on AT-modified and C18-modified catalysts. Acetylene hydrogenation, which results in uncontrolled crowding due to carbonaceous "coke" formation on the catalyst, was found to be insensitive to modification by the thiols. For hydrogenation reactions less associated with uncontrolled coking, crowding - and therefore reactivity - could be controlled systematically using SAMs. In particular, ethylene hydrogenation was 17 times faster on AT-coated surfaces than on C18-coated surfaces, consistent with the additional accessibility to specific sites unavailable on C18-modified surfaces. The effect of modifier density on reactivity was found to be dramatically different for several mono- and bi-functional reactants in a manner consistent with previous literature reports, suggesting that controlled crowding with SAMs can be used to understand reaction structure sensitivity and active site requirements in catalysis.
Structure/activity relationships applied to the hydrogenation of α,β-unsaturated carbonyls: The hydrogenation of 3-butyne-2-one over alumina-supported palladium catalysts
Morisse, Clément G.A.,McInroy, Alastair R.,Anderson, Craig,Mitchell, Christopher J.,Parker, Stewart F.,Lennon, David
, p. 110 - 118 (2017)
The gas phase hydrogenation of 3-butyne-2-one, an alkynic ketone, over two alumina-supported palladium catalysts is investigated using infrared spectroscopy in a batch reactor at 373?K. The mean particle size of the palladium crystallites of the two catalysts are comparable (2.4?±?0.1?nm). One catalyst (Pd(NO3)2/Al2O3) is prepared from a palladium(II) nitrate precursor, whereas the other catalyst (PdCl2/Al2O3) is prepared using palladium(II) chloride as the Pd precursor compound. A three-stage sequential process is observed with the Pd(NO3)2/Al2O3catalyst facilitating complete reduction all the way through to 2-butanol. However, hydrogenation stops at 2-butanone with the PdCl2/Al2O3catalyst. The inability of the PdCl2/Al2O3catalyst to reduce 2-butanone is attributed to the inaccessibility of edge sites on this catalyst, which are blocked by chlorine retention originating from the catalyst's preparative process. The reaction profiles observed for the hydrogenation of this alkynic ketone are consistent with the site-selective chemistry recently reported for the hydrogenation of crotonaldehyde, an alkenic aldehyde, over the same two catalysts. Thus, it is suggested that a previously postulated structure/activity relationship may be generic for the hydrogenation of α,β-unsaturated carbonyl compounds over supported Pd catalysts.
SELECTIVE REDUCTION OF RACEMIC 1,2-BUTYLENE OXIDE WITH (-)-DIISOPINOCAMPHEYLBORANE IN THE PRESENCE OF LITHIUM CHLORIDE
Yoon, Nung Min,Cha, Jin Soon
, p. 5181 - 5184 (1982)
Two equivalents of 1,2-butylene oxide was reduced with one equivalent of (-)-diisopinocampheylborane lithium chloride (1:0.1) system at 0 deg C and -20 deg C to give optically active R-2-butanol, 22.0percent e.e. and 22.6percent e.e., respectively.
Decomposition of Pyridinyltriazenes in Aqueous Buffer: A Kinetic and Mechanistic Investigation
Farnsworth, David W.,Wink, David A.,Roscher, Nina M.,Michejda, Christopher J.,Smith, Richard H.
, p. 5942 - 5950 (1994)
1-(X)-pyridinyl)-3-butyltriazenes (X-PBT), where X = 2,3, or 4, were prepared as prototypes of new chemotherapeutic agents.The acid-catalyzed decomposition of the 1-(X-pyridinyl)-3-butyltriazenes leads to the formation of the corresponding aminopyridines and butyl alcohols. pH-rate profiles, determined over a pH range of 3.5-12.00, show sigmoidal curves with slopes asymptotically approaching 0 at the extremes.The transitions have slopes where rate is inversely proportional to pH, indicating regions of acid catalysis.The solvent kinetic isotope effect, kH2O/kD2O, for each reaction is a from 8.95 to 10.4 and concentrations from 0.03 to 0.15 M, indicates negligible variation in the rate constants.These data strongly support the conclusion that the decomposition is specific acid catalyzed (A1) for each X-PBT isomer.This implies that the reactions involve fast, reversible protonation followed by the rate-determining heterolysis of the protonated species to the n-butyldiazonium ion and X-aminopyridine.Near neutral pH, the half-lives of the 2- and 4-isomers are ca. 100-fold shorter than that of the 3-isomer.This difference can be explained by protonation of the pyridinyl N, which leads to the direct dissociation only for the 2- and 4-isomers.Experimental pKa''s were obtained for each isomer: 2-PBT, 5.19 +/- 0.19; 3-PBT, 4.89 +/- 0.12; 4-PBT, 7.77 +/- 0.16.These values are lower than, but follow the same order as, the pKa values for the analogous isomers of aminopyridine.
The effect of cavitating ultrasound on the heterogeneous aqueous hydrogenation of 3-buten-2-ol on Pd-black
Disselkamp, Robert S.,Chin, Ya-Hueis,Peden
, p. 552 - 555 (2004)
The effect of ultrasound at 20 kHz on the heterogeneous aqueous hydrogenation of 3-buten-2-ol employing a Pd-black catalyst has been studied isothermally at 295 K, forming 2-butanone and 2-butanol products. Our work here shows that adding 1-pentanol as an inert dopant had the effect of inducing cavitation in the ultrasound-treated reaction where it otherwise would not occur. The selectivity showed a 700% increase toward 2-butanol formation and the activity enhanced a factor of 10.8 compared to the noncavitating high-power ultrasound experiment. This study demonstrates that "inert dopants" may have use as synthetic tools in sonocatalysis.
Anodic oxidation of isoalkylethers in aqueous electrolytes
Beck, Fritz,Wermeckes, Bernd,Janssen, Wolfgang
, p. 725 - 736 (1991)
Three isoalkylethers, di-sec-butylether (DSBE), di-i-propylether (DIPE) and t-butylmethylether (TBME) were oxidized in 1 M H2SO4 (mostly as emulsions) at Pt anodes. Solubility was improved by cosolvents, e.g. CH3CN. The standard current density was 750 A m-2. Methylethylketone MEK was the main product, obtained with c.e. of 50 % (yield 70 %), for the cleavage of DSBE. Acetone was found with 68 % c.e. and 66 % yield for the decomposition of DIPE. Acetic acid was the main side product in both cases. TBME was anodically cleaved into t-butanol with 83 % c.e. In case of DSBE, the reaction has some industrial interest, for it transforms a useless side product of butene hydration to a valuable product MEK.
Hydrolytic Stability of Alkyl 1H-Benzotriazolecarboxylates
Jacobi, Sylvia,Hoffmann, Hermann
, p. 89 - 92 (1989)
Hydrolysis of 1H-benzotriazolecarboxylates was studied in 0.1 M NaOH, phosphate buffer pH 7.4 and using a microsomal esterase preparation.Results obtained for the alkaline hydrolysis qualitatively resembled those of enzymatic hydrolysis.In phosphate buffer pH 7.4 the esters were sufficiently stable concerning their use as potential substrates for in vitro biotransformation studies.
The Mechanism of Hydrogenolysis and Isomerization of Oxacycloalkanes on Metals. Part 8. New Results on the Mechanism of Hydrogenolysis of Oxiranes on Platinum and Palladium
Notheisz, Ferenc,Zsigmond, Agnes G.,Bartok, Mihaly,Schmith, Gerard V.
, p. 2359 - 2364 (1987)
The transformations of methyloxirane and cis- and trans-2,3-dimethyloxirane have been studied on Pt/C and Pd/C catalysts at 373 K in the hydrogen pressure range 2-70 kPa in a circulation reactor.The reactions of the dimethyloxirane isomers proceed by similar mechanisms, the rate-determining step in both cases presumably being cleavage of the C-O bond.The mechanism for methyloxirane differs from that for the dimethyloxiranes.One mechanism involves edgewise adsorption of the oxirane (probably via two non-bonding electron pairs), while the other involves flat-lying adsorption.The change in regioselectivity with increase in hydrogen pressures caused by supression of the adsorption of oxygen via two electron pairs.
Enzymatic Oxidation of Butane to 2-Butanol in a Bubble Column
Perz, Frederic,Bormann, Sebastian,Ulber, Roland,Alcalde, Miguel,Bubenheim, Paul,Hollmann, Frank,Holtmann, Dirk,Liese, Andreas
, p. 3666 - 3669 (2020)
Unspecific peroxygenases have recently gained significant interest due to their ability to catalyse the hydroxylation of non-activated C?H bonds using only hydrogen peroxide as a co-substrate. However, the development of preparative processes has so far mostly concentrated on benzylic hydroxylations using liquid substrates. Herein, we demonstrate the application of a peroxygenase for the hydroxylation of the inert, gaseous substrate butane to 2-butanol in a bubble column reactor. The influence of hydrogen peroxide feed rate and enzyme loading on product formation, overoxidation to butanone and catalytic efficiency is investigated at 200 mL scale. The process is scaled up to 2 L and coupled with continuous extraction. This setup allowed the production of 115 mmol 2-butanol and 70 mmol butanone with an overall total turnover number (TTN) of over 15.000, thereby demonstrating the applicability of peroxygenases for preparative hydroxylation of such inert, gaseous substrates at mild reaction conditions.
