ABSTRACT
Surface discharge plasma reactors (SDRs) have been shown to be effective in removing a wide range of pollutants. In this study, the effectiveness of a SDR for the removal of propane and propene from an atmospheric pressure air stream was investigated. For an input energy of 100 J L-1, the conversions were found to be 16% and 68% for propane and propene, respectively. The total carbon recovery was found to increase with increasing specific input energy (SIE) for both hydrocarbons. FTIR analysis showed that CO and CO2 are the major end-products, and GC-MS identified formic acid as a significant byproduct. The effect of initial propane concentration was also investigated. The reaction chemistry involved in the oxidative plasma conversion of propane and propene is discussed.
ABSTRACT
The dynamic fliplike motion in the (R)-thalidomide dimer has been reported for the first time. The vibrational circular dichroism (VCD) spectrum of (R)-thalidomide in DMSO-d6 indicates the characteristic nu(CO) bands with opposite signs and reflects the structural property of the equatorial configuration of the phthalimide ring. On the other hand, the VCD spectrum of (R)-thalidomide in CDCl3 exhibits a different pattern of nu(CO) bands and suggests the fliplike motion in dimer forms. This novel insight for the dimer forms would be helpful for the understanding of the structure-activity relationship for thalidomide.
Subject(s)
Thalidomide/chemistry , Circular Dichroism , Dimerization , Models, Molecular , Molecular Conformation , VibrationABSTRACT
The odd-even effect of chiral alkyl alcohols, (S)-CH(3)CHOHC(n)()H(2)(n)()(+1) (n = 2-8), in solution state has been observed spectroscopically for the first time. The vibrational circular dichroism (VCD) bands at 1148 cm(-)(1) exhibit a clear odd-even effect. The observed VCD bands of (R)-(-)-2-hexanol correspond well to those predicted (population weighted). Density functional theory calculations indicate that the most prevalent conformations in solution are the all-trans forms. The odd-even effect of the VCD bands is ascribed to the alternating terminal methyl motions in the alkyl chains relative to fixed motions near the chiral center in the trans conformations. The conformational sensitivity of VCD for the chiral alcohols in the solution state may be useful for the design of liquid crystals and ligands in the future.
ABSTRACT
Gas-solid heterogeneous photocatalytic oxidation of aromatic compounds in air was carried out at room temperature with a fixed bed flow reactor. The deposition of Rh on TiO2 catalyst improved the catalyst durability in benzene photooxidation. The Rh deposition reduced the amounts of carbonaceous materials on the catalyst surface that were the cause of catalyst deactivation. The highest reaction rate was obtained at the Rh loading of 0.5-1.0 wt %. The Rh/TiO2 catalyst was gradually deactivated in prolonged benzene photooxidation, due to the increasing amount of carbonaceous materials on the catalyst surface. XPS studies showed that the gradual deactivation was related to the changes in the oxidation state of the surface Rh metals. The catalysts were regenerated by the treatment of hydrogen reduction after the photoirradiation in humidified air, indicating that Rh(0) was essential for the improvement of the catalyst durability. The catalyst was also regenerated by the heat treatment in N2 flow instead of the hydrogen reduction. Rh deposition was also effective for the improvement of catalyst durability in toluene photooxidation.
Subject(s)
Coloring Agents/chemistry , Hydrocarbons, Aromatic/chemistry , Rhodium/chemistry , Titanium/chemistry , Air Pollution/prevention & control , Catalysis , Oxidation-Reduction , Photochemistry , Temperature , VolatilizationABSTRACT
The determination of the absolute configuration of chiral molecules is an important aspect of molecular stereochemistry. Vibrational circular dichroism (VCD) is the extension of electronic CD into the infrared region where fundamental vibrational transitions occur. VCD has a number of advantages over all previous methods of absolute configuration assignment. The absolute configuration and predominant solution-state conformation in CDCl(3) of the chiral lactone, 5-formyl-cis,cis-1,3,5-trimethyl-3-hydroxymethylcyclohexane-1-carboxylic acid lactone, 1, obtained by the comparison of measured and calculated VCD spectra, are reported. It is found that (-)-1 corresponds to the absolute configuration (1S,3S,5R)-1.
ABSTRACT
The novel synthetic method for dioxa-azawurtzitanes to selectively cap amino groups in amino acids or peptides is described. Mixing the CH(3)CN solution of cis,cis-1,3,5-triformyl-1,3,5-trimethylcyclohexane (2) with the aqueous solution of the equimolar amounts of glycine and NaHCO(3) yields glycine-containing dioxa-azawurtzitane 7-Na. Dioxa-azawurtzitane 7-Na almost quantitatively isomerizes to lactone-imine 9-Na through the hydride-transfer rearrangement in CH(3)CN/H(2)O. Lactone-imine 9-Na also isomerizes to lactam-aldehyde 12-Na in DMSO.
Subject(s)
Aza Compounds/chemical synthesis , Cyclohexanes/chemical synthesis , Glycine , Tricarboxylic Acids/chemical synthesis , Amino Acids/chemistry , Aza Compounds/chemistry , Bridged-Ring Compounds/chemical synthesis , Bridged-Ring Compounds/chemistry , Catalysis , Chemistry, Organic/methods , Cyclohexanes/chemistry , Dioxanes/chemical synthesis , Dioxanes/chemistry , Glycine/analogs & derivatives , Glycine/chemical synthesis , Glycine/chemistry , Hydrogen/chemistry , Imines/chemistry , Lactones/chemistry , Magnetic Resonance Spectroscopy , Molecular Structure , Peptides/chemistry , Stereoisomerism , Tricarboxylic Acids/chemistryABSTRACT
Nonthermal plasma chemical decomposition of bromomethane (CH3Br) was investigated with a coaxial type packed-bed plasma reactor. It has been demonstrated that plasma chemical processing is an effective approach to decompose CH3Br in a wide concentration range. It has been shown that CH3Br decomposition reactivity depends on reactor operating factors such as background gas, O2 concentration, and humidification. Higher decomposition efficiencies can be obtained in dry N2. However, organic byproducts such as BrCN are concurrently produced under deaerated conditions. Water suppresses CH3Br decomposition and also affects the yields of COx (CO and CO2) and organic byproducts due to the involvement of some active species generated from water. The presence of O2 retards CH3Br decomposition by quenching high-energy electrons, while it suppresses organic byproducts and improves COx yield. The reacted carbons in CH3Br are recovered as COx almost quantitatively in air. Higher CO2 selectivities cannot be achieved by increasing O2 concentration. NOx formation, which is accompanied by CH3Br decomposition, can be effectively suppressed by decreasing O2 concentration down to 2%. Furthermore, reaction mechanisms are discussed by comparing the reactivities of CH3Br and its congeners.
