Kinetics and mechanism of diallyl sulfoxide pyrolysis; a combined theoretical and experimental study in the gas phaseIzadyar, M.; Gholami, M. R.
doi: 10.1039/c4ra11403epmid: N/A
A combined experimental and computational study was carried out on the gas phase pyrolysis reaction of diallylsulfoxide. Allyl alcohol and thioacrolein were detected as the major products during a unimolecular reaction. Experimental kinetic studies were carried out via a static system under the pressure of 21–55 torr and temperature of 435.2–475.1 K. Based on the experiments, the reaction is homogeneous and proceeds through a zwitterionic intermediate. Computational studies at the DFT (B3LYP) and QCISD(T) levels with 6-311++G(d,p) basis set indicated a two-step concerted pathway as the possible route. Comparison between the experimental and theoretical activation parameters for the most probable path confirmed a good agreement.
One-pot synthesis of 6,11-dihydro-5H-indolizino[8,7-b]indoles via sequential formation of β-enamino ester, Michael addition and Pictet–Spengler reactionsZhu, Dan; Sun, Jing; Yan, Chao-Guo
doi: 10.1039/c4ra10355fpmid: N/A
β-Enamino esters generated from addition of tryptamines to alkyl propiolates reacted with 3-phenacylideneoxindoles in the presence of anhydrous ZnCl2 to give functionalized 2-pyrrolo-3′-yloxindoles in satisfactory yields, which can be further converted to the corresponding 6,11-dihydro-5H-indolizino[8,7-b]indoles in good yields through a CF3SO3H catalyzed Pictet–Spengler cyclization process. Under similar conditions, when arylamines were used to replace tryptamine, the one-pot domino reaction afforded the functionalized 2-pyrrolo-3′-yloxindoles.
Multifunctional alkoxysilanes prepared by thiol–yne “click” chemistry: their luminescence properties and modification on a silicon surfaceZuo, Yujing; Wang, Dengxu; Zhang, Jie; Feng, Shengyu
doi: 10.1039/c4ra13620apmid: N/A
The photoinitiated radical-based thiol–yne click reaction provides a simple and efficient method for the formulation of diverse alkoxysilanes. Seven alkoxysilanes, namely, 1,2-bis[3-(trimethoxysilyl)propylthio]hexane (T1), 1,2-bis[3-(trimethoxysilyl)propylthio]-3-chloropropane (T2), 1,2-bis[3-(trimethoxysilyl)propylthio]-3-bromopropane (T3), trimethoxy[3-(styrylthio)propyl]silane (T4), 1,2-bis{3-[dimethoxy(methyl)silyl]propylthio}hexane (D1), 1,2-bis{3-[dimethoxy(methyl)silyl]propylthio}-3-chloropropane (D2), and 1,2-bis{3-[dimethoxy(methyl)silyl]propylthio}-3-bromopropane (D3), were synthesized by reacting alkynes with 3-mercaptopropylalkoxysilane in the presence of a photoinitiator. The thiol–yne reactions ran neatly in standard glassware under 100 W UV irradiation. The functionalized trialkoxysilanes were obtained in quantitative to near-quantitative yields with high purity. Results showed that the reaction of synthesized T4 only occurred in the first cycle, and vinyl sulfide adduct was formed with two configurations of Z and E. Moreover, the isomerization of T4 from Z to E configurations was induced under UV irradiation. T1 and D1 showed excellent photoluminescence properties. Molecular calculations were also performed to confirm the experimental results. Computational results revealed that all compounds exhibited relatively large HOMO–LUMO band gaps, making them promising candidates as host materials for emitters and hole–electron blocking materials in OLED displays. In addition, T1, T2, and T3 were selected to modify the surface properties of Si (1, 0, 0), which can then be used for further functionalization or the immobilization of polymers or biomolecules.
A computational study on the mechanism and kinetics of the reaction between CH3CH2S and OHZhang, Tianlei; Wang, Rui; Zhou, Liting; Wang, Zhiyin; Xu, Qiong; Min, Suotian; Wang, Wenliang
doi: 10.1039/c4ra07780fpmid: N/A
The reaction mechanism of CH3CH2S with OH radicals is studied at the CBS-QB3 level of theory. Five substitution processes and eleven addition–elimination channels are identified for the title reaction. The calculated results indicate that addition–elimination channels CH3CHS + H2O, CH2CH2 + HSOH, CH3CHSO + H2 and CH3CH2SH + O are dominant. Other channels may be negligible due to the high barrier heights. Rate constants and branching ratios are estimated by means of the conventional transition state theory with zero curvature tunnelling over the temperature range of 200–3000 K. The calculation shows that the overall rate constant in the temperature of 200–3000 K is mainly dependent on the channels CH3CHS + H2O, CH2CH2 + HSOH and CH3CH2SH + O. The three-parameter expression for the total rate constant is fitted to be ktotal = 7.42 × 10−21T2.63 exp(−772.43/T) cm3 molecule−1 s−1 between 200–3000 K.
Treatment of acetamiprid insecticide from artificially contaminated water by colloidal manganese dioxide in the absence and presence of surfactantsQamruzzaman, ; Nasar, Abu
doi: 10.1039/c4ra09685apmid: N/A
Acetamiprid is one of the most important pesticides and is effective against a number of insects. The increasing use of insecticides in the agricultural field is associated with a significant risk to water resources and aquatic systems. Thus the degradation of such compounds, after fulfillment of their insecticidal role, is essential to eliminate or minimize the contamination of water. The degradative treatment of acetamiprid insecticide from artificially contaminated water by water soluble colloidal MnO2 in acidic medium (HClO4) has been studied spectrophotometrically in the absence and presence of surfactants. The experiments have been performed under the pseudo-first-order reaction conditions with respect to MnO2. The degradation kinetics has been observed to be first-order with respect to MnO2 while fractional-order in both acetamiprid and HClO4. The anionic surfactant, sodium dodecyl sulfate (SDS) has been observed to be ineffective. On the other hand the reaction in the presence of cationic surfactant, cetyltrimethyl ammonium bromide (CTAB) could not be followed as well because it possesses a positive charge opposite to that of colloidal MnO2 causing flocculation and therefore could not be studied further. However, the addition of non-ionic surfactant, polyethylene glycol tert-octylphenyl ether (TX-100) accelerates the reaction rate. The catalytic effect of TX-100 has been discussed in the light of the available mathematical model. The kinetic data have been exploited to generate the various activation parameters for the oxidative degradation of acetamiprid by colloidal MnO2 in the absence and presence of non-ionic surfactant, TX-100.
Exploring the catalytic activity of new water soluble dinuclear copper(ii) complexes towards the glycoside hydrolysisHaldar, Shobhraj; Patra, Ayan; Bera, Manindranath
doi: 10.1039/c4ra09800epmid: N/A
Two water soluble dinuclear copper(ii) complexes of a new dinucleating ligand, H3phpda [H3phpda = N,N′-bis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine-N,N′-dipropionic acid] have been synthesized and characterized for the investigation of catalytic hydrolysis of glycosides. In methanol, the reaction of stoichiometric amounts of Cu(OAc)2·H2O and the ligand H3phpda in the presence of NaOH, produced a new water soluble dinuclear copper(ii) complex, [Cu2(phpda)(μ-OAc)] (1). Similarly, the reaction of stoichiometric amounts of Cu(ClO4)2·6H2O and the ligand H3phpda in the presence of NaOH, in methanol, afforded a new water soluble dinuclear copper(ii) complex, [Cu2(phpda) (H2O)2](ClO4) (2). Characterizations of the complexes have been performed using various analytical techniques including DFT calculation. The DFT optimized structure of complex 1 shows that two copper(ii) centers are in a distorted square pyramidal geometry with Cu⋯Cu separation of 3.677 Å. On the other hand, the DFT optimized structure of complex 2 reveals that one copper(ii) center adopts a five-coordinate distorted square pyramidal geometry and the other copper(ii) center is in a distorted square planar geometry with Cu⋯Cu separation of 3.553 Å. Further, the mass spectroscopic analyses of complexes 1 and 2 reconfirm their dimeric nature, even in solution. Glycosidase-like activity of complexes 1 and 2 has been evaluated in aqueous solution at pH ∼ 10.5 by UV-vis spectrophotometric techniques using p-nitrophenyl-α-d-glucopyranoside and p-nitrophenyl-β-d-glucopyranoside as the model substrates. Both complexes are active in catalyzing the hydrolysis of glycosides. DFT calculation has been performed to find the Fukui functions at the metal centers in complexes 1 and 2 to predict the possible metal sites involved in the binding process with substrates during the catalytic hydrolysis reactions.
GaN:Pr3+ nanostructures for red solid state light emissionRodrigues, J.; Ben Sedrine, N.; Felizardo, M.; Soares, M. J.; Alves, E.; Neves, A. J.; Fellmann, V.; Tourbot, G.; Auzelle, T.; Daudin, B.; Boćkowski, M.; Lorenz, K.; Monteiro, T.
doi: 10.1039/c4ra08571jpmid: N/A
The photoluminescence of praseodymium implanted and annealed GaN films, quantum wells, nanowires and quantum dots was studied. After implantation and annealing, Pr3+ intra-shell luminescence was achieved for all the analysed samples. In the trivalent charge state the ions' luminescence was found to be dominated by the red lines of the 3P0 → 3F2 transition. In the case of GaN films, an intense red emission is observed with the naked eye at room temperature. Photoluminescence excitation indicates that the preferential population mechanisms of this emission are achieved by using excitation above the GaN band gap. A correlation of the optically active ions' luminescence spectral shape and peak position in the different structures is established. For the GaN nanowires the 3P0 → 3F2 lines of the Pr3+ ions are in good agreement with those identified in GaN films. In the case of GaN quantum dots, the ions' emission was found to be similar to that observed in AlN layers. For AlN/GaN/AlN quantum wells a similar behaviour was identified with the sharp ionic luminescence lines superimposed as a broad band, likely generated by the overlap of multiple Pr-centres. The ionic luminescence stability was analysed and discussed for all the studied samples.
Laser-induced cross-linking GFP-AcmA′ bioprobe for screening Gram-positive bacteria on a biochipLin, Chuen-Fu; Lin, Che-Kuan; Liu, Yi-Jui; Chiang, Chung-Han; Pan, Ming-Jeng; Baldeck, Patrice P.; Lin, Chih-Lang
doi: 10.1039/c4ra12600apmid: N/A
A serviceable bioprobe is one of the important components for the development of microfluidic and lab-on-a-chip systems. In this paper, we report a novel bioprobe, fabricated by laser-induced cross-linking technology, for simple and direct screening of Gram-positive bacteria on a biochip. The AcmA′ protein is known to bind specifically to peptidoglycan (PG), which forms the thick outside layer of Gram-positive bacteria. Moreover, the AcmA′ protein has a much broader spectrum of bacterium types than do antibodies that are more specific to only one bacterium type, because the AcmA′ protein is a generic characteristic of Gram-positive bacteria. Green fluorescent protein (GFP) is generally used as a molecular marker. In this study, GFP was fused with the AcmA′ protein to act as an indicator to trace the AcmA′ binding activity on PG by green fluorescence. The GFP-AcmA′ protein was three-dimensionally structured by laser-induced cross-linking photochemistry technology to fabricate a bioprobe for capturing Gram-positive bacteria. Positive and negative tests on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and Streptococcus agalactiae were demonstrated, respectively. Screening is readily performed using optical microscopy observation. The experiments show that only Gram-positive bacteria were bound on the GFP-AcmA′ probes after minutes of incubation and phosphate buffered saline (PBS) rinsing. No binding was observed with the Gram-negative bacteria or with reference probes composed of neutral bovine serum albumin (BSA). Repeated experiments indicate that our bioprobes are reusable. Finally, a 3D wedge-shaped GFP-AcmA′ probe was demonstrated in a microfluidic channel. This study provides a novel platform for convenient Gram-positive bacteria screening that could potentially be used in lab-on-a-chip applications.