Efficient method for the direct preparation of aryl carboxylates from carboxylic acids using tosyl chloride under solvent-free conditions

A simple, clean and efficient solvent-free procedure for the preparation of aryl carboxylates is described from the direct reaction of carboxylic acids and phenols, in the presence of 1-methylimidazole as base and tosyl chloride (TsCl) as coupling agent. This method can be easily applied for different substituted phenols and carboxylic acids. It can also be applied for the selective acylation when other functional group such as hydroxyl is present on phenol ring.     

Coated wire silver-ion selective electrode based on a N,N'-bis(2-thienylmethylene)-1,2-diaminobenzene.

A novel membrane coated platinum-wire electrode (MCPWE) based on N,N'-bis(2-thienylmethylene)-1,2-diaminobenzene (BTMD) for highly selective determination of Ag+ ion has been developed. The influences of membrane composition and pH on the potentiometric responses of electrode were investigated. The potentiometric responses are independent of the pH of the test solution in the range of 5.0 - 9.0. The electrode shows a linear response for Ag+ ion over the concentration range of 1.0 x 10(-60 to 1.0 x 10(-1) M with a lower detection limit of 6.0 x 10(-7) M. The electrode possesses a Nernstian slope of 59.7 mV decade(-1) and a fast response time of < or = 17 s and can be used for at least 2 months without any observable deviation. The proposed electrode displayed very good selectivity for Ag+ ion with respect to NH4+ and alkali, alkaline earth and some common transition metal ions. The practical utility of the electrode has been demonstrated by its use as the indicator electrode in the potentiometric titration of an AgNO3 solution with a NaI solution and in determination of the silver content of a developed radiological film.     

Mechanism for collision-induced transitions between Λ-doublets in 1Π molecules: Reduction to a single scattering potential

The theory is presented for rotational excitation of ¹Π molecules by collisions with rare gas atoms. It is shown that collision dynamics are described by the two electronic potential energy surfaces which correlate with the electronically degenerate Λ components (doublets) in the diatomic molecule. Because the ±Λ degeneracy can alternatively be described as being in the rotational rather than in the electronic degree of freedom, one can reformulate the collision dynamics in terms of a single effective electronic potential which then depends on Φ, the angle of rotation about the diatomic axis. The form of this Φ dependence is found to be identical to that postulated to explain experimental data for collisional transfer of laser-induced fluorescence.     

Resonance-enhanced multiphoton ionization of molecular hydrogen via the E,F1Σg+ state: Photoelectron energy and angular distributions

Photoelectron energy and angular distributions are measured for the 2+1 multiphoton ionization process H₂ X¹Σ_g⁺ (ν = 0,J) + 2hv → E,F¹Σ_g⁺(ν_E,J_E = J) + hν → H₂⁺X²Σ_g⁺ (ν⁺) + e^?, for ν_E = 0, 1, or 2 and for J_E = 0 or 1 of the inner well of the double-minimum E,F state. Although a strong preference is found for ν⁺ = ν_E, the detailed H₂⁺ vibrational distribution does not exhibit Franck-Condon behavior, and the photoelectron angular distributions vary markedly with both the J_E value of the intermediate state and the ν⁺ value of the ion.     

Determination of D0o(BaI) from the chemiluminescent reaction Ba + I2

A study is made of the visible chemiluminescence resulting from the reaction of an atomic beam of barium with I_Z under single-collision conditions (～ 10^?4 torr). The resulting spectrum consists of the BaI C²Π → X²Σ emission on top of an underlying “continuum”. The variation of the BaI emission intensity with Ba and I₂ flux is investigated, and it is concluded that the reaction is bimolecular. The total phenomenological cross section for barium atom removal is determined to be 86 A², which agrees well with the total reactive cross section calculated assuming an electron jump mechanism. The short wavelength cutoff is identified as the transition from the υ′ = 41 level of the BaI C²Π_{$\text{3}\text{2}$} state to the υ′ = 41 level of the BaI X²Σ state. A strict lower bound D^o₀(BaI) ? 102 ± 0.7 kcal/mole for the ground state dissociation energy of BaI is obtained from this short wavelength cutoff. The value D^o₀(BaI) = 102 ± 1 kcal/mole is recommended, where the error estimate includes the possible contribution from the final relative translational energy of the products.     

Photopolymerized sol-gel frits for packed columns in capillary electrochromatography

Porous sol-gel frits are fabricated in a capillary column by filling it with a solution of 3-(trimethoxysilyl)propyl methacrylate, hydrochloric acid, water, toluene (porogen), and a photoinitiator (Irgacure 1800) and exposing it to UV light at 365 nm for 5 min. The separation column (30 cm x 75 microm I.D.) contains between the inlet and outlet frits a 15-cm packed segment filled with 5-microm silica particles modified with the chiral compound (S)-N-3,5-dinitrobenzoyl-1-naphthylglycine. A detection window (1 mm long) is placed immediately after the outlet frit. To demonstrate the performance of this chiral separation column, mixtures of 16 different amino acids (three of which are not naturally occurring) derivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazole were separated by capillary chromatography. The enantiomeric separation of the column results in a resolution ranging from 1.21 to 8.29, and a plate height ranging from 8.7 to 39 microm.     

Relativistic Oscillators in a Noncommutative Space and in a Magnetic Field

In this work, we study the relativistic oscillators in a noncommutative space and in a magnetic field. It is shown that the effect of the magnetic field may compete withthat of the noncommutative space and that is able to vanish the effect of the noncommutative space.     

Ab initio calculation of the spin-rotation constant for 2Π diatomics: Test of the Van Vleck approximation

Ab initio calculations are carried out to determine γ^Π (true), the first-order contribution to the spin-rotation constant, γ^Π, for the X²Π ground states of OH, HF⁺, and HCl⁺ and their deuterated analogs. These calculations demonstrate that the contribution of this term to the experimentally determined value of γ^Π is small, as has been previously conjectured. Furthermore, it is found in the cases under study that the Van Vleck approximation to γ^Π (true) significantly overestimates its importance, and a more realistic approximation is presented.