Hydrogenation Of Carbonyl Group Research Articles

Cyclometalated iridium complexes for transfer hydrogenation of carbonyl groups in water

Cyclometalated iridium complexes are shown to be excellent catalysts for transfer hydrogenation of carbonyl compounds in water using formate as a hydrogen source. A wide range of ketones and aldehydes have been reduced at 0.05% catalyst loading with no need for any organic solvents. Solution pH is found to play a critical role, with acidic conditions needed for fast transfer hydrogenation.

Preparation of mesoporous oxides and their support effects on Pt nanoparticle catalysts in catalytic hydrogenation of furfural

Mesoporous SiO2, Al2O3, TiO2, Nb2O5, and Ta2O5 were synthesized through a soft-templating approach by a self-assembled framework of Pluronic P123 and utilized for the preparation of 3-dimensional catalysts as supports. Colloidal Pt nanoparticles with an average diameter of 1.9nm were incorporated into the mesoporous oxides by sonication-induced capillary inclusion. The Pt nanoparticles supported on mesoporous oxides were evaluated in the hydrogenation reaction of furfural (70torr furfural and 700torr H2 with a balance of He) to study the effect of catalyst supports on selectivity. In the temperature ranges of 170–240°C, the major products of this reaction were furan, furfuryl alcohol, and 2-methyl furan through a main reaction pathway of either decarbonylation or carbonyl group hydrogenation. While Pt nanoparticles with the size ranges of 1.5–7.1 exhibited strong structure-dependent selectivity, various supports loaded with only 1.9nm Pt nanoparticles produced dominantly furan as a major product. Compared to the inert silica support, TiO2 and Nb2O5 facilitated an increase in the production of furfuryl alcohol via carbonyl group hydrogenation as a result of a charge transfer interaction between the Pt and the acidic surface of the oxides. The same trend was confirmed on 2-dimensional type catalysts, in which thin films of SiO2, Al2O3, TiO2, Nb2O5, and ZrO2 were prepared as supports. When furfural hydrogenation was conducted (1torr furfural, 100torr H2, and 659torr He) over Pt nanoparticle monolayers deposited on oxide substrates, only TiO2 was shown to increase the production of furfuryl alcohol, while other oxides produced furan.

Iron-catalysed reduction of carbonyls and olefins

The transition metal-catalysed reduction of olefins and carbonyl groups are amongst the most used reactions in synthetic chemistry. Recent developments using iron catalysts have shown that iron species are able to equal the activity of the traditionally used transition metals in these reductions. This review will focus on the iron-catalysed hydrosilylation, hydrogenation and transfer hydrogenation of carbonyl groups and the hydrogenation of olefins.

Preparation of 1-phenylethanol by selective hydrogenation of acetophenone over alumina-supported Co catalysts

Alumina-supported cobalt metal catalysts are studied in the preparation of 1-phenylethanol by the selective hydrogenation of acetophenone. X-ray diffraction was used to investigate the phase of the catalysts. Effects of reaction temperatures, Co loading, and catalysts preparation method on the activity of the hydrogenation of acetophenone and the selectivity of 1-phenylethanol were studied. The results show that the preparation method and Co loading influence the dispersion of the catalyst. The hydrogenation of carbonyl groups has priority to hydrogenation of phenyl groups over alumina-supported Co catalysts. The selectivity of 1-phenylethanol decreases when the reaction temperature is increased under the same conversion conditions. With the Co loading increasing, the reaction activity increases while the selectivity of 1-phenylethanol decreases. The selectivity of 1-phenylethanol reaches 98% when the conversion is up to 98.2% at 373 K over the catalyst prepared by impregnation.

Effect of Particle Structure and Surface Chemistry on PMMA Adsorption to Silica Nanoparticles

The interphase layer of polymers adsorbed to silica surfaces can be affected by the surface silanol density as well as the relative size of the polymer compared with the size of the adsorbing substrate. Here, the nonequilibrium adsorption of PMMA onto individual colloidal Stober silica (SiO(2)) particles, where R(particle) (100 nm) > R(PMMA) (approximately 6.5 nm) was compared with the adsorption onto fumed silica, where R(particle) (7 nm) approximately R(PMMA) (6.5 nm) < R(aggregate) (approximately 1000 nm), as a function of both silanol density [SiOH] and hydrophobility. In the former case, TEM images showed that the PMMA adsorbed onto individual nanoparticles, so that the number of PMMA chains/bead could be calculated, whereas in the latter case bridging of PMMA between aggregates occurred. The anchoring point densities were comparable to the silanol densities, suggesting that PMMA adsorbed as trains rather than loops. For hydrophilic SiO(2), T(g) increased with [SiOH], as more carbonyl groups hydrogen bonded to the silanols, and was independent of particle morphology. For methylated silica, (CH(3))(3)SiO(2), the adsorption isotherms were identical for colloidal and fumed silica, but T(g) was depressed for the former, and comparable to the bulk value for the latter. The increased T(g) of PMMA adsorbed onto fumed (CH(3))(3)SiO(2) was attributed to the larger loops formed by the bridging PMMA chains between the silica aggregates.

Infrared spectroscopy of liquid water– N, N-dimethylformamide mixtures

The real and imaginary molar polarisability spectra ( α′ m (ν̃) and α″ m (ν̃), respectively) of mixtures of water and N, N-dimethylformamide (DMF) over the full composition range (0 ≤ x DMF ≤ 1) at 25 °C were determined between 4000 and 700 cm − 1 by using a calibrated single reflection attenuated total reflection (ATR) technique. The composition dependent mole fractions of OH groups hydrogen bonded to water or DMF, together with the fractions of carbonyl groups hydrogen bonded to water or free were obtained from the integral intensities C OH, and C CO of the ν(OH) and ν(CO) bands, respectively. As for the acetonitrile-water system (studied by other groups), a continuous composition dependence of the mole fraction of OH oscillators in different bonding situations was found with practically the same segmentation of the full composition range ( x I = 0.2–0.3, x II = 0.7–0.8). From these observations, the existence of relatively large, stable water or DMF aggregates is proposed for x DMF between x I and x II with hydrogen bonding between water and DMF occuring only at the interfaces between the aggregates.

Orientational Motions of Vibrational Chromophores in Molecules at the Air/Water Interface with Time-Resolved Sum Frequency Generation

The first time-resolved experiments in which interfacial molecules are pumped to excited electronic states and probed by vibrational sum frequency generation (SFG) are reported. This method was used to measure the out-of-plane rotation dynamics, i.e. time dependent changes in the polar angle, of a vibrational chromophore of an interfacial molecule. The chromophore is the carbonyl group, the rotation observed is that of the -C=O bond axis, with respect to the interfacial normal, and the interfacial molecule is coumarin 314 (C314) at the air/water interface. The orientational relaxation time was found to be 220+/-20 ps, which is much faster than the orientational relaxation time of the permanent dipole moment axis of C314 at the same interface, as obtained from pump-second harmonic probe experiments. Possible effects on the rotation of the -C=O bond axis due to the carbonyl group hydrogen bonding with interfacial water are discussed. From the measured equilibrium orientation of the permanent dipole moment axis and the carbonyl axis, and knowledge of their relative orientation in the molecule, the absolute orientation of C314 at the air/water interface is obtained.

Carbon‐Carbon Double Bond versus Carbonyl Group Hydrogenation: Controlling the Intramolecular Selectivity with Polyaniline‐Supported Platinum Catalysts

AbstractThe use of polyaniline (PANI) as catalyst support for heterogeneous catalysts and their application in chemical catalysis is hitherto rather poorly known. We report the successful synthesis of highly dispersed PANI‐supported platinum catalysts (particle sizes between 1.7 and 3.7 nm as revealed by transmission electron microscopy, TEM) choosing two different approaches, namely (i) deposition‐precipitation of H2PtCl6 onto polyaniline, suspended in basic medium (DP method) and, (ii) immobilization of a preformed nanoscale platinum colloid on polyaniline (sol‐method). The PANI‐supported platinum catalysts were applied in the selective hydrogenation of the α,β‐unsaturated aldehyde citral. In order to benchmark their catalytic performance, citral hydrogenation was also carried out by using platinum supported on the classical support materials silica (SiO2), alumina (Al2O3), active carbon and graphite. The relations of the structural characteristics and surface state of the catalysts with respect to their hydrogenation properties have been probed by EXAFS and XPS. It is found that the DP method yields chemically prepared PtO2 on polyaniline and, thus, produces a highly dispersed and immobilized Adams catalyst (in the β‐PtO2 form) which is able to efficiently hydrogenate the conjugated CC bond of citral (selectivity to citronellal=87%), whereas reduction of the CO group occurs with polyaniline‐supported platinum (selectivity to geraniol/nerol=78%) prepared via the sol‐method. The complete reversal of the selectivity between the preferred hydrogenation of the conjugated CC or CO group is not only particularly useful for the selective hydrogenation of α,β‐unsaturated aldehydes but also unveils the great potential of conducting polymer‐supported precious metals in the field of hitherto barely investigated chemical catalysis.

Synthesis, characterization and catalytic application of Ru II–ethylenediamine complex—mesoporous silica as heterogeneous catalyst system in chemo-selective hydrogenation of α,β-unsaturated carbonyl compounds

An efficient heterogeneous catalyst system for chemo-selective hydrogenation of α,β-unsaturated aldehydes was synthesized, involving anchoring of a Ru II–phosphine complex on the inner surfaces of organo-functionalized (propylamine and propylethylenediamine) mesoporous MCM-41 and MCM-48 materials. Powder XRD, SEM and TEM experiments reveal highly ordered hexagonal and cubic patterns of the organically modified MCM-41 and MCM-48 materials, respectively, even after incorporation of Ru complexes. Moreover, the integrity of the Ru complex was retained after anchoring into the mesoporous hosts, which was supported by FTIR, 31P CP MAS NMR and XPS analyses. This heterogeneous catalyst shows promising activity and chemo-selectivity towards hydrogenation of carbonyl groups in α,β-unsaturated aldehydes. The effects of reaction temperature, reaction time and hydrogen pressure on the activity and selectivity were studied in detail. The anchored solid catalysts can be recycled effectively and reused several times without any loss in activity and selectivity. Although, the initial activity of the same Ru complex when grafted onto the organically modified surfaces of fumed silica is comparable to corresponding MCM-41/MCM-48 catalysts, the activity and chemo-selectivity significantly decrease during recycle of the catalyst due to leaching.

Structured but not over-structured: Woven active carbon fibre matt catalyst

Catalytic hydrogenation of citral was studied on a Pt on active carbon cloth (ACC) catalyst, with a Pd in ionic liquid on ACC and a commercial Pt on active carbon powder catalysts. The metal was supported on active carbon either by direct impregnation or utilizing the ionic liquid as the intermediate phase on the carbon. The influence on selectivity and activity, of the most important variables, such as temperature and pressure, was investigated in a batch reactor. Four consecutive experiments were carried out with each catalyst. The aim with the reuse of catalysts in the batch reactor was to elucidate eventual catalyst deactivation. The decrease in activity was very notable in the case of traditional impregnated catalysts, whereas the novel SSIL-TM (structured supported ionic liquid-transition metal) or Pd in ionic liquid on active carbon essentially maintained its activity in four consecutive batches. The catalysts were characterized with scanning electron microscopy, N 2 physisorption, and inductively coupled plasma analysis combined with mass spectroscopy. With the Pt on active carbon fibre catalyst, 80–100% selectivity of carbonyl group hydrogenation was achieved at 15% conversion, whereas the Pd in ionic liquid on ACC catalyst displayed an impressive metal efficiency (citral-to-Pd ratio of 156, mol:mol), selectivity (45%) and activity (92% conversion at 140 min) as well as tolerance towards catalyst deactivation. Supported ionic liquids provide a new reaction environment for catalytic transformations.

Novel woven active carbon fiber catalyst in the hydrogenation of citral

Catalytic hydrogenation of citral was performed in a batch reactor under elevated pressures. The reaction was studied with a Pt on active carbon fiber catalyst and a commercial Pt on active carbon powder catalyst. Platinum was supported on active carbon by impregnation. The influence on selectivity and activity, of the most important variables, such as temperature and pressure, was investigated in the batch reactor. Four consecutive experiments were carried out with each catalyst. The aim with the reuse of catalysts in the batch reactor was to elucidate eventual catalyst deactivation. The decrease in activity was fairly notable. The catalysts were characterized with scanning electron microscopy, N 2-physisorption, and inductively coupled plasma analysis combined with mass spectroscopy. With the Pt on active carbon fiber catalyst, 80–100% selectivity of carbonyl group hydrogenation was achieved at 15% conversion.

Hydrogenation of Carbonyl Groups

AbstractFor Abstract see ChemInform Abstract in Full Text.

Mesoporous silica-supported Ni [sbnd]B amorphous alloy catalysts for selective hydrogenation of 2-ethylanthraquinone

The effects of pore structure on the reaction rates and selectivities in the liquid-phase hydrogenation of 2-ethylanthraquinone over Ni B amorphous alloy catalysts prepared by the reductant-impregnation method were studied using regular (HMS, MCM-41, and SBA-15) and commercial mesoporous silicas as supports. The composition, particle size, and location of the Ni B particles were profoundly influenced by the pore structure of the supports. It is found that the location of the Ni B particles depended on the pore size of the supports, whereas the uniformity of particle size was related to the interaction between the Ni B particles and the supports. The hydrogenation rate was much faster on Ni B catalysts with pore diameters exceeding 5 nm than on the narrow-pore catalysts, whereas the selectivity to 2-ethyldihydroanthraquinone, the carbonyl group hydrogenation product, was higher on Ni B catalysts supported on regular mesoporous silicas. The best activity and selectivity were achieved when using SBA-15 as the support, which is attributable to the formation of more uniform active sites due to the unique pore structure of SBA-15.

Reduction of chloroacetone over silica-supported noble metal catalysts

The reduction of chloroacetone over silica-supported noble metal catalysts yielded the hydrodechlorinated (acetone), the hydrogenated (1-chloro-2-propanol), and the hydrodechlorinated–hydrogenated (2-propanol) products at different selectivities depending on the catalyst used. Pd/SiO2 catalyzed the single-step hydrodechlorination preferentially to give acetone selectively. Pt/SiO2 promoted the hydrogenation into 1-chloro-2-propanol concurrently and the consecutive hydrogenation of acetone into 2-propanol as well. Over Rh/SiO2, acetone was transformed to 1-chloro-2-propanol through the addition of hydrogen chloride. The hydrodechlorination activity of noble metals followed the order of Pd > Pt ⪢ Rh > Ru.The high selectivity of Pd/SiO2 toward acetone was not influenced by Pd dispersion. The selectivity of Pt/SiO2 changed largely with Pt dispersion and the hydrogenation of carbonyl group was promoted preferentially over the catalysts with low Pt dispersion.

Structure of a complex of the potent and specific inhibitor BW284C51 with Torpedo californica acetylcholinesterase.

The X-ray crystal structure of Torpedo californica acetylcholinesterase (TcAChE) complexed with BW284C51 [CO[-CH(2)CH(2)-pC(6)H(4)-N(CH(3))(2)(CH(2)-CH=CH(2))](2)] is described and compared with the complexes of two other active-site gorge-spanning inhibitors, decamethonium and E2020. The inhibitor was soaked into TcAChE crystals in the trigonal space group P3(1)21, yielding a complex which diffracted to 2.85 A resolution. The structure was refined to an R factor of 19.0% and an R(free) of 23.4%; the final model contains the protein, inhibitor, 132 water molecules and three carbohydrate moieties. BW284C51 binds similarly to decamethonium and E2020, with its two phenyl and quaternary amino end-groups complexed to Trp84 in the catalytic site and to Trp279 in the peripheral binding site, and its central carbonyl group hydrogen bonded very weakly to Tyr121. Possible reasons for decamethonium's weaker binding are considered. The relative strength of binding of bisquaternary inhibitors to acetylcholinesterase and the effect of several mutations of the enzyme are discussed in the context of the respective X-ray structures of their complexes with the enzyme.

Antibiotic activity of valinomycin Molecular dynamics simulations involving the water/membrane interface

Molecular dynamics (MD) simulations, covering 550 ps of equilibration and 100 ps of production, of the adsorption of the antibiotic valinomycin (VM) and the dissociation reaction of its potassium complex at the two interfaces of a hydrophobic membrane bounded by water, are reported. The simulation addresses questions pertaining to the structure and behaviour of this important antibiotic in the interfacial region and represent the first study of ion decomplexation at an atomistically detailed interface. The system involves a total of 18866 atomic sites, including four VM molecules and four complexes. The simulation shows uncomplexed VM to be a surfactant. Owing to the flexibility of the VM ring the uncomplexed molecule readily adopts novel conformations at the interface with non-polar groups embedded in the membrane and the carbonyl groups hydrogen bonded with water. These conformations are quite distinct from those seen in the solid state or in bulk solution. The observed flattening of the molecule against the interface is in excellent accord with experimental measurements of molecular shape at the water/air interface and on the surface of lipid bilayers. Although complex formation with K + ions is not observed on the timescale of the simulation, the decomplexation reaction occurs spontaneously on a timescale of 20–30 ps and shows noticeable orientation effects. At the interface, the K + is selectively released through the Lac face of the bracelet-like complex, in contrast to release through the HyV face in aqueous or methanol solution. At the interface, the release mechanism consists of the gradual replacement of ester carbonyl groups by water molecules in the first coordination sphere of K + . The evidence from the simulation suggests that the rate-determining step for decomplexation is the orientational ordering of the complex at the interface and not the formation of intermediate water adducts.

ChemInform Abstract: Stereo‐ and Chemoselective Transfer Hydrogenation of Carbonyl Groups with RuCl2(PPh3)3 and BINAP‐Ru as Catalysts and Et3NH+H2PO‐ 2×1, 5 H2O as a Hydrogen Donor.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stereo- and chemoselective transfer hydrogenation of carbonyl groups with RuCl 2(PPh 3) 3 and BINAP-Ru as catalysts and Et 3NH +H 2PO 2−·1,5H 2O as a hydrogen donor

Using Et 3NH +H 2PO 2 −.1.5 H 2O as a hydrogen donor, the RuCl 2(Ph 3P) 3, RuCl 2(PPh 3) 3 C and BINAP-Ru proved highly active catalysts for transfer hydrogenation of ketones under milder conditions than other hydrogen donors. 2-Methyl-, 2-chloro-, 2-(ethoxy-carbonyl)cyclohexanones and -cyclopentanones were reduced to the less stable axial alcohols in excellent diastereoisomeric excess (de: 90–100%), and the carbonyl group of α,β-unsaturated ketones was selectively reduced, in contrast with other hydrogen donors the CC bond was reduced.

Effect of daptomycin on the barotropic behavior of dioleoylphosphatidylglycerol: an infrared spectroscopic investigation

According to our infrared spectra, the pressure-induced liquid-crystal to gel transition of dioleoylphosphatidylglycerol (DOPG) involves a conformational change making the glycerol C sn−1 − C sn−2 bond more parallel to the bilayer surface and resulting in increased carbonyl groups hydrogen bonding. This conformational change allows a more compact packing of the cis unsaturated acyl chains. The lipopeptide daptomycin, at lipid/daptomycin molar ratios of 4:1, impedes the DOPG conformational change and induces an increase of transition pressure from 5.5 (pure lipid) to 6.8 kbar and a higher disorder in the gel state. The analogue (LY298862) of daptomycin containing a myristoyl instead of a decanoyl chain shifts the phase transition to 7.8 kbar at the same molar ratio and reduces more efficiently the lipid conformational change. The lipopeptide hydrocarbon chain length is thus a critical parameter in the modulation of the physical effects of this type of compounds, often used as antibiotics.

Catalytic Hydrogenation of Acetophenone Over Ruthenium Catalysts

Catalytic hydrogenation of acetophenone in ethanol was studied by using 5 wt.% Ru supported on active carbon, alumina, and titania. Parameters of kinetic equations (reaction rate constants and adsorption coefficients) were evaluated and the influence of the support on the reaction course was discussed. An enhanced selectivity of Ru/TiO2 towards carbonyl group hydrogenation with respect to the hydrogenation of the aromatic ring was confirmed.