2188-31-0Relevant academic research and scientific papers
Photocatalytic Oxidation of Ethanol: Isotopic Labeling and Transient Reaction
Muggli, Darrin S.,Larson, Sheldon A.,Falconer, John L.
, p. 15886 - 15889 (1996)
Transient reaction techniques were combined with isotope labeling to study the reaction steps for the room-temperature, photocatalytic oxidation (PCO) of ethanol on TiO2.Carbon-13 labeled ethanol (CH3(13)CH2OH) was adsorbed on the catalyst and photocatalytically oxidized in the absence of gas-phase ethanol.The amounts of species remaining on the surface after PCO were determined by temperature-programmed oxidation.During PCO, only CO2 and H2O formed for low coverages of ethanol, whereas acetaldehyde also desorbed for saturation coverage.Acetaldehyde forms rapidly from ethanol oxidation during PCO.At both low and high ethanol coverages, the α-carbon is preferentially oxidized and thus (13)CO2 forms faster than (12)CO2 at short illumination times.At longer times, the rates of (13)CO2 and (12)CO2 formation are nearly identical.The difference in behavior between (13)CO2 and (12)CO2 formation suggests two parallel reactions of ethanol, which may be due to two adsorption sites on TiO2.
Ring current effects in the active site of medium-chain Acyl-CoA dehydrogenase revealed by NMR spectroscopy
Wu, Jiaquan,Bell, Alasdair F.,Jaye, Andrew A.,Tonge, Peter J.
, p. 8424 - 8432 (2005)
Medium-chain acyl-CoA dehydrogenase (MCAD) catalyzes the flavin-dependent oxidation of fatty acyl-CoAs to the corresponding frans-2-enoyl-CoAs. The interaction of hexadienoyl-CoA (HO-CoA), a product analogue, with recombinant pig MCAD (pMCAD) has been studied using 13C NMR and 1H-13C HSQC spectroscopy. Upon binding to oxidized pMCAD, the chemical shifts of the C1, C2, and C3 HD carbons are shifted upfield by 12.8, 2.1, and 13.8 ppm, respectively. In addition, the 1H chemical shift of the C3-H is also shifted upfield by 1.31 ppm while the chemical shift of the C4 HD-CoA carbon is unchanged upon binding. These changes in chemical shift are unexpected given the results of previous Raman studies which revealed that the C3=C2-C1=O HD enone fragment is polarized upon binding to MCAD such that the electron density at the C3 and C1 carbons is reduced, not increased (Pellet et al. Biochemistry 2000, 39, 13982-13992). To investigate the apparent discrepancy between the NMR and Raman data for HD-CoA bound to MCAD, 13C NMR spectra have been obtained for HD-CoA bound to enoyl-CoA hydratase, an enzyme system that has also previously been studied using Raman spectroscopy. Significantly, binding to enoyl-CoA hydratase causes the chemical shifts of the C1 and C3 HD carbons to move downfield by 4.8 and 5.6 ppm, respectively, while the C2 resonance moves upfield by 2.2 ppm, in close agreement with the alterations in electron density at these carbons predicted from Raman spectroscopy (Bell, A. F.; Wu, J.; Feng, Y.; Tonge, P. J. Biochemistry 2001, 40, 1725-33). The large increase in shielding experienced by the C1 and C3 HD carbons in the HD-CoA/MCAD complex is proposed to arise from the ring current field from the isoalloxazine portion of the flavin cofactor. The flavin ring current, which is only present when the enzyme is placed in an external magnetic field, also explains the differences in 13C NMR chemical shifts for acetoacetyl-CoA when bound as an enolate to MCAD and enoyl-CoA hydratase and is used to rationalize the observation that the line widths of the C1 and C3 resonances are narrower when the ligands are bound to MCAD than when they are free in the protein solution.
A straightforward implementation of in situ solution electrochemical 13C NMR spectroscopy for studying reactions on commercial electrocatalysts: Ethanol oxidation
Huang,Sorte,Sun,Tong
, p. 8086 - 8088 (2015/05/20)
Identifying and quantifying electrocatalytic-reaction-generated solution species, be they reaction intermediates or products, are highly desirable in terms of understanding the associated reaction mechanisms. We report herein a straightforward implementation of in situ solution electrochemical 13C NMR spectroscopy for the first time that enables in situ studies of reactions on commercial fuel-cell electrocatalysts (Pt and PtRu blacks). Using ethanol oxidation reaction (EOR) as a working example, we discovered that (1) the complete oxidation of ethanol to CO2 only took place dominantly at the very beginning of a potentiostatic chronoamperometric (CA) measurement and (2) the PtRu had a much higher activity in catalysing oxygen insertion reaction that leads to acetic acid.
Partial oxidation of ethane to oxygenates using Fe- and Cu-containing ZSM-5
Forde, Michael M.,Armstrong, Robert D.,Hammond, Ceri,He, Qian,Jenkins, Robert L.,Kondrat, Simon A.,Dimitratos, Nikolaos,Lopez-Sanchez, Jose Antonio,Taylor, Stuart H.,Willock, David,Kiely, Christopher J.,Hutchings, Graham John
supporting information, p. 11087 - 11099 (2013/08/23)
Iron and copper containing ZSM-5 catalysts are effective for the partial oxidation of ethane with hydrogen peroxide giving combined oxygenate selectivities and productivities of up to 95.2% and 65 mol kgcat -1 h-1, respectively. High conversion of ethane (ca. 56%) to acetic acid (ca. 70% selectivity) can be observed. Detailed studies of this catalytic system reveal a complex reaction network in which the oxidation of ethane gives a range of C2 oxygenates, with sequential C-C bond cleavage generating C1 products. We demonstrate that ethene is also formed and can be subsequently oxidized. Ethanol can be directly produced from ethane, and does not originate from the decomposition of its corresponding alkylperoxy species, ethyl hydroperoxide. In contrast to our previously proposed mechanism for methane oxidation over similar zeolite catalysts, the mechanism of ethane oxidation involves carbon-based radicals, which lead to the high conversions we observe.
Molecular Structure of s-cis- and s-trans-Acrolein Determined by Microwave Spectroscopy
Blom, C. E.,Grassi, G.,Bauder, A
, p. 7427 - 7431 (2007/10/02)
The rotational spectra of highly enriched single D-, 13C-, and 18O-substituted species of acrolein have been measured and analyzed over 12-58 GHz.The complete substitution structure has been determined for the less abundant s-cis conformer from the ground-state rotational constants.In addition newly assigned μb-type transitions for all isotopic species of the more abundant s-trans-acrolein have improved the structure of this conformer.Careful measurements of the Stark effect have resulted in an accurate determination of the electric dipole moment of the s-trans conformer.A comparison of the molecular structures of the two conformers has revealed significant differences in the central C-C bonds.
