Molecular damage in bi-isonicotinic acid adsorbed on rutile TiO2(1 1 0)

Here we present the characteristic signatures in X-ray absorption and photoemission spectroscopy for molecular damage in adsorbed monolayers of bi-isonicotinic acid on a rutile TiO₂(1 1 0) surface. Bi-isonicotinic acid is the anchor ligand through which many important inorganic complexes are bound to the surface of TiO₂ in dye-sensitized solar cells. The nature of the damage caused by excessive heating of the adsorbed monolayer is consistent with splitting the molecule into two adsorbed isonicotinic acid molecular fragments. The effect on the lowest unoccupied molecular orbitals (involved in electron transfer in the molecule) can be understood in terms of the adsorption geometry of the reaction products and their nearest neighbor interactions.     

Differentiation of Regioisomeric Aromatic Ketocarboxylic Acids by Positive Mode Atmospheric Pressure Chemical Ionization Collision-Activated Dissociation Tandem Mass Spectrometry in a Linear Quadrupole Ion Trap Mass Spectrometer

Positive-mode atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS ⁿ ) was tested for the differentiation of regioisomeric aromatic ketocarboxylic acids. Each analyte forms exclusively an abundant protonated molecule upon ionization via positive-mode APCI in a commercial linear quadrupole ion trap (LQIT) mass spectrometer. Energy-resolved collision-activated dissociation (CAD) experiments carried out on the protonated analytes revealed fragmentation patterns that varied based on the location of the functional groups. Unambiguous differentiation between the regioisomers was achieved in each case by observing different fragmentation patterns, different relative abundances of ion-molecule reaction products, or different relative abundances of fragment ions formed at different collision energies. The mechanisms of some of the reactions were examined by H/D exchange reactions and molecular orbital calculations.     

Microwave assisted synthesis of bridgehead alkenes

A new, concise method to synthesize triene precursors for the type 2 intramolecular Diels-Alder reaction has been developed. Microwave irradiation of the trienes provides a convenient method for the synthesis of bridgehead alkenes. Higher yields, shorter reaction times, and lower reaction temperatures provide a general and efficient route to this interesting class of molecules.     

The Synthesis of 1-Methyl-6,7,8,8a-tetrahydro-5H-indolizin-3-one by the Palladium-Catalyzed Cyclization of N-Bromoacetyl-2-vinylpiperidine

N-Bromoacetyl-2-vinylpiperidine underwent cyclization to give indolizidine derivative in the presence of a base and a catalytic amount of palladium trifluoroacetate.     

Reaction pathways and kinetic parameters of sonolytically induced oxidation of dimethyl methylphosphonate in air saturated aqueous solutions

The oxidation of dimethyl methylphosphonate (DMMP) was examined under ultrasonic conditions (640 kHz) in oxygen saturated aqueous solutions. Acetic acid, formic acid, methylphosphonic acid, phosphate, and oxalic acid have been identified as the major products produced during the sonolytic irradiation of DMMP. The initial rates of oxidation were determined as a function of initial DMMP concentration. The kinetic behavior of the system is consistent with the Langmuir-Hinshelwood model implying oxidative processes occur at or near the gas-liquid interface during cavitation. Mechanistic implications and conclusions are discussed based on the product distributions and kinetic parameters.     

Sound scattering by a potential vortex

The scattering of a monopole wavefield by the flow of a potential vortex is considered by using a scheme due to Lighthill. The problem is two-dimensional, the monopole being a line source adjacent to a parallel line vortex. The cases of large and small separation of vortex and source are examined in detail. The far field density is asymptotically estimated in both limits. A quadrupole type radiation field is calculated in each case.     

Dual function catalysts. Dehydrogenation and asymmetric intramolecular Diels-Alder cycloaddition of N-hydroxy formate esters and hydroxamic acids: evidence for a ruthenium-acylnitroso intermediate

The chiral ruthenium salen complex, 13b, functions as an efficient catalyst for the sequential oxidation and asymmetric Diels-Alder cycloaddition of hydroxamic acids and N-hydroxy formate esters. This result provides evidence for the formation of a ruthenium-nitroso formate (acyl nitroso) intermediate. The Diels-Alder precursors are prepared from simple building blocks, and the cycloadducts, bridged oxazinolactams, can serve as useful intermediates in organic synthesis.     

The interaction of 605 MeV 63Cu with 197Au

Binary coincident fragments from the ⁶³Cu + ¹⁹⁷Au reaction at a copper energy of 605 MeV have been studied. Fragment energies were measured and fragment masses determined by a kinematic method. Three types of event are defined by suitable adjacent limits in the mass versus total kinetic energy event space. The angular distributions of cross section, average total kinetic energy and average mass have been determined for each event region. Total cross sections determined in the present experiment are compared to those found at lower bombarding energies. Further information on the sequential fission process has been obtained from measurements of yields of radioactive isotopes resulting from bombardment ofthin and thick targets of Au by 605 MeV Cu ions.     

Dynamics of a monolayer of nitrogen physisorbed on graphite

The dynamics of a crystalline monolayer of molecular nitrogen physisorbed on the basal plane of graphite, which was assumed to be rigid, has been studied by means of lattice and molecular dynamics. The study focusses mainly on the registered solid in which the centres of mass adopt the √3 × √3 R30° structure, but some results are also reported for denser monlayers, including one where the centre-of-mass lattice is non-triangular. Harmonic dispersion curves are reported for two models of the N₂-N₂ interaction combined with Steele's representation of the molecule-surface interaction. The one-phonon density of states is given for one of the models. Molecular dynamics results for the same model at two temperatures, 5 and 17 K, are analysed in terms of the dynamical structure factor, and one-phonon approximation to it, and the out-of-plane motions are treated in a manner similar to the one-phonon approximation. In-plane and out-of-plane motions are largely decoupled in all cases studied, and the in-plane motions show evidence of marked anharmonicity. The out-of-plane motions appear to exhibit Fermi-Pasta-Ulam type recurrences, although this is not analysed in detail.