Synthesis of 1-oxadecalins from anisole promoted by tungsten

The complex TpW(NO)(PMe3)(eta(2)-anisole) is combined with acrolein or methyl vinyl ketone and various nucleophiles to generate novel chromen complexes. These complexes may be further elaborated by protonation and nucleophilic addition to generate chroman analogues with increased saturation and stereocenters. Treatment with various oxidants effects the decomplexation of the chromen.     

Time-resolved velocity map imaging of methyl elimination from photoexcited anisole

To date, H-atom elimination from heteroaromatic molecules following UV excitation has been extensively studied, with the focus on key biological molecules such as chromophores of DNA bases and amino acids. Extending these studies to look at elimination of other non-hydride photoproducts is essential in creating a more complete picture of the photochemistry of these biomolecules in the gas-phase. To this effect, CH(3) elimination in anisole has been studied using time-resolved velocity map imaging (TR-VMI) for the first time, providing both time and energy information on the dynamics following photoexcitation at 200 nm. The extra dimension of energy afforded by these measurements has enabled us to address the role of πσ* states in the excited state dynamics of anisole as compared to the hydride counterpart (phenol), providing strong evidence to suggest that only CH(3) fragments eliminated with high kinetic energy are due to direct dissociation involving a (1)πσ* state. These measurements also suggest that indirect mechanisms such as statistical unimolecular decay could be contributing to the dynamics at much longer times.     

The vibrational spectrum of anisole

The infrared and Raman spectra of C₆H₅OCD₃, C₆D₅OCH₃ and C₆D₅OCD₃ have been recorded in the liquid state. Vibrational assignments have been made and values for most of the fundamental vibrations have been obtained and correlated with those of C₆H₅OCH₃. Studies of the ultraviolet absorption spectrum have provided gas-phase data on a number of totally symmetric modes.     

On the mechanism of spray formation from liquid jets

A fundamental physical mechanism whereby sprays are formed from liquid jets is formulated. It is shown that a combination of axial disturbances cannot produce the necessary conditions for non-axial evolution of drops. These conditions are satisfied by a non-axial sequence of superimposed disturbances, propagating one on top of the other. The resulting model is used to describe the evolution of liquid jets into sprays. It is postulated that every consecutive superimposed disturbance, which is characterized by a self-instability parameter, travels tangent to the surface that supports its propagation. Model outputs show that starting from the first superimposed disturbance, highly complex profiles of the jet surface are generated. Fourier analysis of the derived superimposed disturbance functions is performed in conjunction with the basic building blocks of classic instability theory. This is achieved by assigning to each term a self-instability factor. The sum of these building blocks results in intricate profiles of the jet. In these profiles, multiplicity of radial position of the jet interface as a function of axial distance provides the necessary conditions for evolution of non-axial drops. The model accuracy, which depends on the disturbance rank, is sufficient to disclose the mechanism that turns the jet into a spray. The observed jump in the level of error is commensurate with the sudden increase in flow complexity that follows an increase in the disturbance rank. Finally, model outputs are used to study the effect of instability parameters on the evolution patterns of the jet and the non-axial discharge of drops.     

On the question of allene formation from tricyclic cyclopropylidenes

The carbenoid or carbene derived from $\text{8}$ undergoes dimerization or trapping with DPIBF. The allene mechanism previously proposed was made doubtful by the finding that stereoisomeric carbenes

and

give stereoisomeric products without crossover.     

The composition of catalysts prepared from tri-n-propylaluminum,anisole, and titanium tetrachloride

Catalysts were prepared from titanium tetrachloride and tri-n-propylaluminum or tri-n-propylaluminum anisole at [Al]/[Ti] molar ratios of 0.20–1.10. They were aged and filtered, and the solid and liquid portions were analyzed for aluminum, titanium, chlorine, and certain organic constituents. The analyses indicate that the solid of the nonetherate catalyst is predominantly TiCl₃, some AlCl₃ or aluminum alkyl chlorides being included. Only at [Al]/[Ti] = 1.10 was any alkyl group found in the solid. The same general results were found for the etherate catalyst, but the solid had a somewhat lower [Cl]/[Ti] ratio, indicating greater reduction or alkylation, or both, of the titanium species than in the nonetherate catalyst. The solid also contained some anisole at the higher [Al]/[Ti] ratios. The results lend general support to proposed reactions for the catalyst formation. The main differences in the etherate catalysts relative to the non-etherate system, particularly at the higher [Al]/[Ti] ratios, are the apparently greater reduction or alkylation of the titanium in the solids, the presence of anisole in the liquid and solid portions, and the presence of phenol in the liquid portion. The phenol presumably comes from cleavage of the anisole during the catalyst formation. Not all of the anisole has been accounted for in a materials balance, nor has all of the chlorine in the etherate catalysts. No propyl or isopropyl chloride was found in the catalysts; there is no significant amount of polypropylene in any of the catalyst solids. Hence the fate of the alkyl groups remains undetermined at present.     

On the possibility of dioxirane formation from criegee peroxide adducts

The possibility of dioxirane formation from thermal and cesium fluoride induced decomposition of α-t-butyldimethylsilyloxyalkyl peroxypenzoates has been examined.     

On the formation of multilayers in adsorption from binary liquid mixtures

Summary A new excess isotherm is derived for multilayer adsorption from binary liquid mixtures on solid surfaces. This is done by applying the Myers and Sircar's theoretical procedure, and assuming that the adsorption of single components is described by the BET isotherm equation, as modified by Brunauer, Skalny and Bodor. The derived excess equation is next generalized for the case of patchwise heterogeneous solid surfaces. The illustrative calculations presented here include both model investigations and an investigation of two real adsorption systems. It is drawn as a general conclusion that the heterogeneity effects in adsorption from solutions play a greater role than previously supposed.

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Zusammenfassung Eine neue Excessisotherme wurde für vielschichtige Adsorption aus Zweikomponentlösungen an festen Oberflächen abgeleitet. Das wurde mit Anwendung der theoretischen Methode von Myers und Sircar durchgeführt, wobei angenommen wurde, daß die Adsorption der einzelnen Komponenten durch die BET-Gleichung in der Modifizierung von Brunauer, Skalny und Bodor ausgedrückt wird. Die abgeleitete Excessgleichung wurde dann für heterogene feste Oberflächen generalisiert. Die Berechnungen berücksichtigen beide Untersuchungsmodelle und die Untersuchungen der zwei realen Adsorptionssysteme. Es wurde festgestellt, daß der Einfluß der Heterogenität in Adsorption von Lösungen eine größere Rolle spielt, als es vorher angenommen wurde.

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With 9 figures and 1 table     

KBr催化剂上DMC与苯酚甲基化合成苯甲醚的反应机理研究

结合原位FT-IR,热力学分析及反应规律研究了KBr催化剂上碳酸二甲酯（DMC）氧位甲基化苯酚合成苯甲醚的反应机理。FT-IR显示KBr催化剂高于100℃活化苯酚生成酚盐,但至200℃也不活化DMC。共吸附的FT-IR及反应数据均显示苯甲醚高于150℃时生成。反应中检测到少量羰基甲氧基化产物苯基甲基碳酸酯（MPC）先于苯甲醚而生成,结合热力学计算及MPC分解转化的实验结果分析,生成MPC的反应是与生成苯甲醚的甲基化反应并行的可逆副反应。甲基化反应的机理为苯酚先被去质子化而形成酚盐,高于150℃时,酚盐的酚氧负离子亲核进攻DMC的甲基碳而生成苯甲醚。     

On the mechanism of peripentacene formation from pentacene: computational studies of a prototype for graphene formation from smaller acenes

The formation of peripentacene during the high-temperature vacuum sublimation of pentacene (P) in the presence of trace amounts of 6,13-dihydropentacene (DHP) has been studied computationally with density functional theory. Computational and kinetic analyses indicate that competing mechanisms involving a series of H atom transfers initiated by hydrogen transfer from DHP to P can account for the formation of peripentacene. The overall reaction is predicted to proceed with a free energy barrier of 36.1 kcal/mol and to be autocatalytic. Kinetic modeling supports the proposed mechanism.     

On the importance of purity for the formation of self-assembled monolayers from thiocyanates

Assembly of dodecyl thiocyanate (C12SCN) from ethanol solution onto Au(111)/mica substrates was investigated by scanning tunneling microscopy (STM), near edge X-ray absorption fine structure spectroscopy (NEXAFS), X-ray photoelectron spectroscopy (XPS), and infrared reflection-absorption spectroscopy (IRRAS). Contrary to previous reports, thiolate monolayers formed by cleavage of the S-CN bond can be obtained whose quality is at least as good as that of self-assembled monolayers (SAMs) formed directly from the thiol analogue of C12SCN, dodecanethiol (C12SH). However, the achievable quality is strikingly dependent on the purity of the thiocyanate with even low levels of contamination impeding the formation of structurally well-defined monolayers.     

On the mechanism of dioxygen formation from a di-mu-oxo-bridged manganese dinuclear complex

Density functional theory (DFT) calculations, using the Becke-Perdew gradient-corrected functional with a triple-zeta-plus-polarization basis set, have been used to characterize the [(H(2)O)(H(3)N)(3)Mn(mu-O)(2)Mn(NH(3))(3)(OH(2))](q)(+) (q = 2-5) complexes. This structure has been proposed as a possible model for the oxygen-releasing site of the photosystem II (PSII) reaction center. We have performed full optimizations to locate stationary points in various spin states for each of the +2 to +5 charge states. Our calculations indicate that O(2) release from the vacuum-phase +5 charge state complex is barrier inhibited, in contrast to the results of a recent DFT study. We report several new di-mu-oxo-bridged stationary points with spin multiplicities of S = (1)/(2), (3)/(2), and (5)/(2) and effective metal oxidation states of Mn(IV)Mn(V) for the +5 charge state. Finally, calculations employing the 'conductorlike screening model' (COSMO), to address the inclusion of solvent effects, indicate that dissociative O(2) release from the +5 charge state model complex is inhibited by a major barrier and is therefore apparently highly disfavored.     

Spectroscopic properties of anisole in mixed polar solvents

Absorption and emission spectra, fluorescence quantum yields and lifetimes were studied for anisole in binary ethanol-water mixtures. The spectroscopic and photophysical properties show an exceptional behaviour in the aqueous solution. In water a strong nonradiative process, originating from the fluorescent state decreases the emission yield and lifetime. The results are discussed in terms of short range interactions between the solute and solvent.     

On the formation and properties of a high-temperature resin from a bisphthalonitrile

When 4,4'-bis (3,4-dicyanophenoxy) biphenyl is heated with small amounts of aromatic amine or amidine salts, a highly crosslinked polytriazine is obtained. This polymer has been shown to be the same as that reported when bisphthalonitriles are heated with amines. Salts promote this reaction more readily and the glass transition temperature of the polymer after post-cure at 315°C is generally 30°C higher than when free bases are used. The fracture properties and elasticity of the salt-cured polymer have been measured at temperatures up to 250°C. As a model system, the self reaction of phthalonitrile promoted by amines and their salts has been studied. In both cases, poly[4-(2-cyanophenyl)-1,3,5-triazine-2,6-diyl-1,2-phenylene] is produced, and more efficiently using the salts. A reaction mechanism for this polymerization has been proposed. © 1994 John Wiley & Sons, Inc.