Crossed beam reaction of phenyl and D5-phenyl radicals with propene and deuterated counterparts--competing atomic hydrogen and methyl loss pathways

We conducted the crossed molecular beams reactions of the phenyl and D5-phenyl radicals with propylene together with its partially deuterated reactants at collision energies of ~45 kJ mol(-1) under single collision conditions. The scattering dynamics were found to be indirect and were mainly dictated by an addition of the phenyl radical to the sterically accessible CH(2) unit of the propylene reactant. The resulting doublet radical isomerized to multiple C(9)H(11) intermediates, which were found to be long-lived, decomposing in competing methyl group loss and atomic hydrogen loss pathways with the methyl group loss leading to styrene (C(6)H(5)C(2)H(3)) and the atomic hydrogen loss forming C(9)H(10) isomers cis/trans 1-phenylpropene (CH(3)CHCHC(6)H(5)) and 3-phenylpropene (C(6)H(5)CH(2)C(2)H(3)). Fractions of the methyl versus hydrogen loss channels of 68 ± 16% : 32 ± 10% were derived experimentally, which agrees nicely with RRKM theory. As the collision energy rises to 200 kJmol(-1), the contribution of the methyl loss channel decreases sharply to typically 25%; the decreased importance of the methyl group loss channel was also demonstrated in previous crossed beam experiments conducted at elevated collision energies of 130-193 kJ mol(-1). The presented work highlights the interesting differences of the branching ratios with rising collision energies in the reaction dynamics of phenyl radicals with unsaturated hydrocarbons related to combustion processes. The facility of forming styrene, a common molecule found in combustion against the elusiveness of forming the cyclic indane molecule demonstrates the need to continue to explore the potential surfaces through the combinative single collision experiment and electronic structure calculations.     

Recent advances on the chemistry of transition metal complexes of 2-(arylazo)pyridines and its arylamino derivatives

Recent advancement on the redox properties of a selection of transition metal complexes of the azoaromatic ligands: bidentate L(1) [2-(arylazo)pyridine] and tridentate HL(2) [2-(aminoarylphenylazo)pyridine] are described and compared. Due to the presence of a low lying azo-centered π*-orbital, these azoaromatic ligands may exist in multiple valent states. The coordination chemistry of the L(1) ligands was thoroughly studied during the 1980s. These complexes undergo facile reduction in solution at low accessible potentials. One electron reduced azo-complexes, though known for a long time to occur in solution, have only recently been isolated in a crystalline state. New synthetic protocols for the synthesis of metal-bound azo-radical complexes have been developed. Low-valent metal complexes such as metal carbonyls have been found to be excellent starting materials for this purpose. In a few selected cases, syntheses of these complexes were also achieved from very high valent metal oxides using triphenylphosphine as both a reducing and oxo-abstracting agent. Issues related to the ambiguities of the electronic structures in the azo-metal complexes have been discussed considering bond parameters, redox and spectral properties. Unusual redox events such as RIET (Redox-Induced Electron Transfer) phenomena in a few systems have been elaborated and compared with the known example. Novel examples of N=N bond cleavage reactions via four-electron reduction and subsequent C-N bond formation in metal-bound coordinated ligands have been noted.     

Direct determination of tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate by HPLC and GC methods

The high performance liquid chromatography and gas chromatography methods were investigated for their applicability in determining micro-level concentrations of tri-n-butyl phosphate (TBP). A high performance liquid chromatograph (HPLC) equipped with refractive index detector was used in determining TBP up to 2 ppm concentration level in the aqueous nitric acid solutions. The gas chromatography incorporated with Thermionic Detector (NPD) and Flame Photometric Detector (FPD) were examined for their potential in analyzing TBP in organic phase up to sub-ppm level. The results indicated that HPLC-RI technique is well suited for direct analysis of aqueous phase. For organic phase analysis, gas chromatographic methods with the TID and FPD were suitable but performance of detectors deteriorated often due to fouling.     

Measurement of the neutron capture cross-section of 238U using the neutron activation technique

The ²³⁸U(n, ??)²³⁹U reaction cross-section at average neutron energy of 3.7?±?0.3?MeV from the ⁷Li(p, n)⁷Be reaction has been determined using activation and off-line ??-ray spectrometric technique. The ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections at average neutron energy of 9.85?±?0.38?MeV from the same ⁷Li(p, n)⁷Be reaction have been also determined using the above technique. The experimentally determined ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections were compared with the evaluated data of ENDF/B-VII, JENDL-4.0, JEFF-3.1 and CENDL-3.1. The experimental values were found to be in general agreement with the evaluated value based on ENDF/B-VII, and JENDL-4.0 but not with the JEFF-3.1 and CENDL-3.1. The present data along with literature data in a wide range of neutron energies were interpreted in terms of competition between different reaction channels including fission. The ²³⁸U(n, ??)²³⁹U and ²³⁸U(n, 2n)²³⁷U reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were also found to be in agreement experimental data.     

Thermal effect on vibration of non-homogenous visco-elastic rectangular plate of linearly varying thickness

An analysis for vibration of non-homogenous visco-elastic rectangular plate of linearly varying thickness subjected to thermal gradient has been discussed in the present investigation. For visco-elastic, the basic elastic and viscous elements are combined. We have taken Kelvin model for visco-elasticity that is the combination of the elastic and viscous elements in parallel. Here the elastic element means the spring and the viscous element means the dashpot. The governing differential equation of motion has been solved by Galerkin’s technique. Deflection, time period and logarithmic decrement at different points for the first two modes of vibration are calculated for various values of thermal gradients, non homogeneity constant, taper constant and aspect ratio for non-homogenous visco-elastic rectangular plate which is clamped on two parallel edges and simply supported on remaining two edges. Comparison studies have been carried out with homogeneous visco-elastic rectangular plate to establish the accuracy and versatility.     

Theory of sheath in a collisional multi-component plasma

The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.     

Incomplete fusion reactions: Analysis of excitation functions and recoil range distributions in 16O + 51V

Incomplete fusion reactions were investigated by measuring the excitation functions of nine evaporation residues in ¹⁶O + ⁵¹V reaction in the beam energy 4-6 MeV/amu, using the well-known recoil catcher technique and gamma-ray spectrometry. The experimental data were compared with that obtained from Monte Carlo simulation calculations using the PACE2 code. The results indicate the presence of incomplete fusion process in the production of two alpha emission products. This was further confirmed by the measurement of recoil range distribution of these isotopes at 96 MeV beam energy. Calculations of the average angular momentum associated with these products revealed the peripheral nature of these ICF reactions. Received: 20 June 2001 / Accepted: 11 September 2001     

1:1 Hetero‐assembly of 2‐amino­pyrimidine and (+)‐camphoric acid

In the title cocrystal, 2‐aminopyrimidine–(+)‐camphoric acid (1/1), C₄H₅N₃·C₁₀H₁₆O₄, the 2‐amino­pyrimidine forms two eight‐membered hydrogen‐bonded rings with two different camphoric acid mol­ecules. This results in infinite wave‐like chains of mol­ecules in which neighbouring chains are connected by weak C—H?O contacts. The five‐membered ring in the acid mol­ecule adopts a half‐chair conformation.     

Antibacterial nano-biocomposite scaffolds of Chitosan,Carboxymethyl Cellulose and Zn & Fe integrated Hydroxyapatite (Chitosan-CMC-FZO@HAp) for bone tissue engineering

Cellulose - The polymeric scaffolds are one of the most studied systems for biomedical applications. Yet, their enzymatic degradation and non-antibacterial ability are the major challenges for the...     

Theory of Jovian Kilometric Radiation

This report presents a theoretical model of extraordinary mode radiation in presence of low frequency whistler mode. We show that the generation mechanism of extraordinary mode emission in the presence of whistler mode is based on the plasma maser theory. Application of theoretical results to Jovian Kilometric radiation is examined.