Abstract  The reactions of trichloromethylium (CCl3+) with benzene and the lower alkyl aromatics (ArH) have been studied by high pressure mass spectrometry at pressures in the range 24 Torr and temperatures from 300 to 560K. The only two primary products are the adduct ArHCCl3+and ArCCl2+, which is formed by loss of HCl from the adduct. The relative yields of adduct increase with increasing number of methyl substituents on the aromatic ring (benzenemesitylene). The disappearance of CCl3+is kinetically second order with specific rate constants increasing from benzene to mesitylene, the latter reacting essentially at every ionmolecule collision. All rate constants are fairly large (>1010ccmolecule1s1) and show negative temperature coefficients. ArCCl2+is unreactive but ArHCCl3+reacts further by proton transfer to ArH.Oprant des pressions allant de 2 4 Torr et des tempratures allant de 300 560K et faisant appel la spectromtrie de masse haute pression, on a tudi les ractions de l'ion trichloromethylium (CCl3+) avec le benzne et les alkylbenznes lgers (ArH). Les deux seuls produits primaires sont l'adduit ArHCCl3+et le ArCCl2+qui se forme partir de l'adduit par la perte de HCl. Les rendements relatifs de l'adduit augmentent avec une augmentation du nombre de substituants mthyles sur le noyau aromatique (benznemsitylne). La disparition du CCl3+est cintiquement du deuxime ordre et les constantes spcifiques de vitesse augmentent lorsqu'on passe du benzne au msitylne; ce dernier ragit essentiellement chaque collision ionmolcule. Toutes les constantes de vitesse sont assez leves (>1010ccmolcule1s1) et elles prsentent toutes des coefficients de temprature qui sont ngatifs. Alors que le ArCCl2+n'est pas ractif, le ArHCCl3+est susceptible de donner d'autres ractions par transfert de proton vers les ArH. [Traduit par le journal]

Abstract  The reactions of CH3ClCH3+(I) and CH3ClCH2Cl+(II) with a range of bases have been studied in a high pressure ion source. Reactant ion monitoring has been used to obtain the relative reactivities. Transfer of CH3+from Iand CH2Cl+from IIare the only reactions observed with N- and O-containing bases. Following addition of CH2Cl+from II, the lower alkyl aromatics (ArH) yield either ArHCH2Cl+or the benzyl ions ArCH2+and ArCHCl+while CH3+transfer leads only to ArHCH3+. The reactivities of the alkyl aromatics increase with increasing exothermicity (benzenemesitylene) and there is an increasingly negative temperature coefficient of reactivity in the same order.On a tudi les ractions du CH3ClCH3+(I) et du CH3ClCH2Cl+(II) avec un certain nombre de bases dans une source d'ions haute pression. On a utilis la technique de l'enregistrement de l'ion qui ragit pour obtenir les ractivits relatives. Les seules ractions observes avec les bases contenant de l'azote ou de l'oxygne sont celles du transfert de CH3+ partir de Iet de CH2Cl+ partir du compos II. Aprs l'addition de CH2Cl+ partir du compos II, les drivs aromatiques alkyls infrieurs (ArH) conduisent soit au ArHCH2Cl+ou aux ions benzyliques ArCH2+et ArCHCl+; par ailleurs, le transfert de CH3+conduit uniquement l'ion ArHCH3+. La ractivit des composs aromatiques alkyls augmente avec l'exothermicit (benznemsitylne) et le coefficient de temprature volue vers des valeurs de plus en plus ngatives lorsqu'on procde dans le mme ordre. [Traduit par le journal]

Abstract  A modified phosphotriester method has been successfully applied for the chemical synthesis of ribooligonucleotides. The starting material is a fully protected ribomononucleoside containing a 3-phosphotriester group 5. The coupling reaction is performed using mesitylenesulfonyl tetrazole and purification of the product achieved using reversed phase column chromatography. The effectiveness of this method has been demonstrated by achieving an efficient and rapid synthesis of r-A7, r-A11, r5-AAACAUGAGGA-3, and r5-UUACCCAUGU-3 (R-17, translation control sequence).On a appliqu avec succs une mthode de phosphotriester modifi la synthse chimique des ribooligonuclotides. On utilise comme produit de dpart un ribonucloside entirement protg contenant un groupe phosphotriester en position 3(5). On a ralis le couplage en utilisant le msitylne sulfonyle ttrazole et on a purifi le produit par chromatographie sur colonne en phase inverse. On dmontre l'efficacit de cette mthode en ralisant une synthse rapide et efficace du r-A7, r-A11, r5-AAACAUGAGGA-3 et du r5-UUACCCAUGU-3 (R-17, unit de contrle de translation). [Traduit par le journal]

Abstract  

The catalytic activity of Pt/-Al_2O_3 membrane reactors, prepared using mesitylene solvated platinum atoms as source of active Pt particles, has been compared with that of analogously obtained Pt/-Al_2O_3 powders in the liquid phase hydrogenation of p-chloronitrobenzene. A largely different behaviour has been observed, the membrane reactor acting as a H_2 richer system.

Abstract  NiPt/HY zeolite catalysts with different Ni contents were prepared and applied to the disproportionation of toluene and 1,2,4-trimethylbenzene in the temperature range 250400 C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. ESCA studies show the complete reduction of Ni species up to 0.3 wt.% Ni addition over 0.1 wt.% Pt/H-Y and further addition leads to the occurrence of unreduced nickel species as NiAl2O4. A TEM study shows the formation of bimetallic (NiPt) particles of nanoscale size and the average particle size is found to increase with increasing Ni loading. Acidity measurements by NH3-TPD and pyridine-adsorbed FTIR spectroscopy show the increasing occupation of acid sites by increasing nickel loading. The catalytic activity of NiPt/HY zeolite and Pt/HY catalysts was compared and it was found that addition of Ni up to 0.3 wt.% increases conversion of toluene and 1,2,4-trimethylbenzene, disproportionation selectivity and sustainability of the catalysts. Further addition of Ni leads to a decrease in conversion and disproportionation selectivity and increasing dealkylated products, which may be due to the presence of unreduced Ni species and pore blockage by large-sized bimetallic particles formed. [ABSTRACT FROM AUTHOR] Copyright of Catalysis Letters is the property of Springer Science & Business Media B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  The effect of the size of gold particles deposited on CeO2 and TiO2 supports on their catalytic behavior in the aerobic oxidation of benzyl alcohol in different solvents (mesitylene, toluene, and supercritical carbon dioxide) has been investigated. The size of supported gold particles deposited via a colloidal route was in the range 1.3-11.3 nm, as determined by means of EXAFS and HAADF-STEM measurements. The catalytic performance of the supported gold catalysts in the different solvents revealed a significant effect of the gold particle size. Optimal activity was observed for catalysts with medium particle size (ca. 6.9 nm) whereas smaller and bigger particles showed inferior activity. Identical trends for the activity-particle size relationship were found using Au/CeO2 and Au/TiO2 for the reaction at atmospheric pressure in conventional solvents (mesitylene, toluene) as well as under supercritical conditions (scCO(2)). Selectivity to benzaldehyde was only weakly affected by the gold particle size and mainly depended on reaction conditions. In supercritical CO2 (scCO(2)) selectivity was higher than in the conventional solvents under atmospheric pressure. All catalysts tested with particle sizes ranging from 1.3 to 11.3 nm showed excellent selectivity of 99% or higher under supercritical conditions.

Abstract  Benzene and substituted derivatives (toluene, ortho-xylene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, anisole), when applied in large excess, react with 1,4 diols (pentan-1,4-diol, hexan-2,5-diol, and 2,5-dimethylhexan-2,5-diol) or an oxolane (2,2,5,5-tetramethyltetrahydrofuran) in the presence of the Bronsted superacid trifluoromethanesulfonic acid (triflic acid, TFSA) to afford substituted tetralins in excellent yields with high selectivity. Reacting benzene with a small excess of alkylating agents yields octahydroanthracenes. The transformation of naphthalene with oxolane leads to a partially saturated octamethyloctahydrotetracene under similar conditions. Product formation is interpreted by intermolecular Friedel-Crafts alkylation followed by cyclialkylative ring closure.

Abstract  Mesitylene solvated platinum atoms have been conveniently used for the deposition of active Pt particles on gamma-Al2O3 SUPports. The so prepared catalysts have been compared with traditionally obtained Pt/gamma-Al2O3 catalysts in the dehydrogenation of methylcyclohexane to toluene, at 200 and 250-degrees-C, showing, at low Pt loadings, a much greater specific activity.

Abstract  The production of various xylenes from toluene, heavy aromatics such as 1,2,4trimethylbenzene (1,2,4TMB) and their mixture was investigated over HZSM5 (HZ), Hmordenite (HM) and a dual zeolitic catalyst comprising ZSM5 and mordenite (HZM). The experiments were conducted in a risersimulator reactor under different operating conditions to study the effect of temperature, reaction time and feed composition on conversion and product yields. At 400C, the conversion of toluene over the three catalysts yielded mainly benzene and xylenes with maximum conversion at 25% and a xylene yield of 12.5 wt% over the HM catalyst. The transformation of 1,2,4TMB doubled the conversion level and xylene yield and suppressed benzene formation. However, a considerable portion of the 1,2,4TMB feed was isomerized into 1,2,3TMB and 1,3,5TMB accompanied by the formation of tetramethylbenzenes (TeMBs). The conversion of an equimolar mixture of toluene and 1,2,4TMB over the three catalysts resulted in higher toluene conversion and double xylene yield in comparison with 1,2,4TMB alone. The advantage of using a dual zeolitic catalyst was observed at an equimolar feed of toluene and 1,2,4TMB, exhibiting maximum toluene conversion, higher xylene yield and the formation of lower levels of undesirable products.

Abstract  The conductance and stretching length of the single C-60 molecule bridging two Au electrodes (C-60 molecular junction) were studied in air, mesitylene and 0.1 M HClO4 solution. In air, the C-60 molecular junction did not show any well-defined conductance value. In either mesitylene or HClO4 solution, the systems showed a conductance value of 0.01G(0). The stretching length of the single C-60 molecular junction was determined to be 0.01 nm. The values of the conductance and stretching length in solution were smaller than those obtained in ultra high vacuum, indicating the weak C-60-Au interaction in solution. Considering the particular shape of the C-60 molecule and the junction formation process in the present system, a sliding model was proposed to interpret the observation. (C) 2009 Published by Elsevier B. V.

Abstract  Novel [3+3]-additions and water (methanol)-incorporated additions were observed in the photoreactions of N-methyl-1,8-naphthalimide with methylbenzenes, such as xylenes, mesitylene, and durene, in acetonitrile. A mechanism for the reactions is proposed on the basis of the fluorescence quenching examinations, calculations of de associated with the electron transfer, and deuteration studies.

Abstract  The self-assembling of fluorescent guest molecules, with the nanoporous host crystalline phase of syndiotactic polystyrene (s-PS) films, reduces chromophore diffusivity. Moreover, the chromophore fluorescence can be largely perturbed by formation of suitable polymer co-crystals. In particular, by excitation at the absorbance maximum (265 nm), s-PS/1,3,5-trimethylbenzene clathrate co-crystals present a broad fluorescence band nearly centered at 300 nm, while the corresponding intercalate co-crystals present a red-shifted fluorescence band with maxima at 330, 340, and 355 nm. This red shifted fluorescence is possibly due to absorption of the primary fluorescence by ground state complexes, formed in the intercalate co-crystal. The enhanced and red-shifted fluorescence could be relevant for optical and optoelectronic applications. [ABSTRACT FROM AUTHOR] Copyright of Chemistry of Materials is the property of American Chemical Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  A novel soft chemical synthesis of Ni1-xAlxnanoparticles (0.09 x 0.50) by cohydrogenolysis of Ni(cod)2(1) with (AlCp)4(2) or with (Me3N)AlH3(3) in nonaqueous solution is presented (cod 1,5-cyclooctadiene, Cp 1,2,3,4,5-cyclopentadienyl). The treatment of equimolar amounts of 1and 2in mesitylene solution under 3 bar of H2at 150 C gave a brown-black colloidal solution of intermetallic -NiAl particles, characterized by transmission electron microscopy/energy dispersive X-ray analysis (TEM/EDX) and powder X-ray diffraction (XRD). The solution was stable under 3 bar of H2at 150 C for up to 8 h. The -NiAl colloids were treated postsynthesis with 17O-enriched 1-adamantanecarboxylic acid (ACA) as a surface capping group, giving nearly monodisperse -NiAl colloids that were stable under argon at room temperature for weeks. The coordination of ACA at the -NiAl surface was studied by 17O NMR and IR spectroscopy. A series of -Ni1-xAlxsamples with a variety of compositions (x0.50, 0.33, 0.25, 0.17, 0.09) were prepared analogously, and the samples were characterized by means of elemental analysis (ICP), XRD, and TEM/EDX. Air oxidation of -Ni1-xAlxnanoparticles leads to coreshell particles of the type (Al2O3)2Ni1-xAlx-(0.09 x 0.50; x> ). XRD, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) analyses showed that the Ni core is protected against oxidation down to an Al content of about 10 atom %. [ABSTRACT FROM AUTHOR] Copyright of Chemistry of Materials is the property of American Chemical Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract  

Trimeric perfluoro-ortho-phenylene mercury (1) dissolves in substituted benzenes including toluene, ortho-xylene, meta-xylene, para-xylene and is sparingly soluble in mesitylene. The ¹⁹⁹Hg NMR resonance of 1 in toluene, ortho-xylene, meta-xylene, and para-xylene appears at 1051.8, 1053.5, 1051.4 and 1059.1 ppm, respectively. These resonances are slightly upfield from the resonance observed for 1 in CH₂Cl₂ ( 1045.2 ppm) and possibly indicates the solvation of the mercury centres by molecules of arenes. Slow evaporation of solutions of 1 in toluene, ortho-xylene, meta-xylene, para-xylene and mesitylene affords 1toluene (2), 1ortho-xylene (3), 1meta-xylene (4), 1para-xylene (5) and 1mesitylene (6), respectively, as crystalline complexes. These adducts have been characterized by elemental analysis and X-ray crystallography. Thermogravimetric analyses indicate that 25 begin to lose the coordinated arene at a temperature below 50 C; however, in the case of 6 loss begins around 91 C. The structures of 2, 4 and 5 reveals the existence of binary stacks in which the aromatic core of the benzenes approaches the mercury centres of 1. In the case of 3 and 6, the aromatic molecule appears preferentially bound to one of the two proximal molecules of 1. Hence, 3 and 6 are best described as discrete 1 1 complexes. In 26, the resulting HgC_aromatic distances are in the range 3.23.5 and are within the sum of the van der Waals radii. They reflect the presence of secondary polyhapto -interactions occurring between the electron-rich aromatic molecules and the acidic mercury centres.

Abstract  This review summarizes our original organometallic route to stars, dendrimers, metallostars and metallodendrimers and the redox functions of these macromolecules in catalysis and anionic recognition. The synthesis of metal-sandwich stars and dendritic cores was achieved using the CpM+ induced polyallylation and polybenzylation of polymethylbenzenes (M = Fe or Ru) and pentamethylcyclopentadienyl ligands (M = Co or Rh). Subsequent functionalization of the polyallyl dendritic cores yielded polyols which are precursors of polyiodo, polymesylates, polynitriles, polyamines and polybenzaldehaldehyde cores. The synthesis of dendrimers up to 144-nitrile and 243-allyl was subsequently achieved starting from mesitylene. Functionalization of the polybenzyl. dendritic cores was achieved by regiospecific Friedel-Crafts reactions (acetylation, chlorocarbonylation) in the para position. Various metallodendrimers were synthesized with amidoferrocene, amidocobaltocenium and FeCp*(eta(6)-N-alkylaniline)(+) termini in which the redox centers show a reversible behavior and are all independent as observed by cyclic voltammetry. The 9-, 18- and 24-amidometallocene dendrimers were used for the recognition of the oxo anions H2PO4- and HSO4- by cyclic voltammetry,whereas a 24-iron-alkylaniline dendrimer was efficient to recognize Cl- and Br- anions by H-1 NMR with sharp dendritic effects. Differences between the responses to the different anions were large and the largest effects were found for the 18-Fc dendrimer (dendritic effect). A water-soluble star-shaped hexa-iron redox catalyst was as efficient as the mononuclear species for the cathodic reduction of NO3- and NO2- in water. In conclusion, metallostars are suitable for catalysis, and metallodendrimers present optimal topologies for molecular recognition. These specific functions related to the topologies cannot be interchanged between the metallostars and the metallodendrimers with optimized efficiency in the present examples.