Epoxidation of alkenes using HOF·MeCN by a continuous flow process

Continuous flow methodology is described which allows the in situ generation of the highly effective oxidising agent HOF·MeCN from fluorine and wet acetonitrile and immediate reaction with alkenes to afford epoxides in high yield. The HOF·MeCN continuous flow oxidising system provides an environmentally benign process that is suitable for large scale synthesis and is atom efficient, because the only by-product is hydrogen fluoride which, in principle, could be recycled to produce fluorine by electrolysis.     

Determination of chemical oxygen demand in fresh waters using flow injection with on-line UV-photocatalytic oxidation and spectrophotometric detection

A flow injection manifold incorporating UV-photocatalytic oxidation for the determination of chemical oxygen demand (COD) in freshwater is reported. The method utilises the UV-photocatalytic oxidation of organic compounds instead of conventional heating (used in the standard method), with acidified potassium permanganate as the oxidant. Sodium oxalate, d-glucose and potassium hydrogen phthalate were used as COD standards. A 100 microL sample solution was injected into a 0.3 mol L(-1) H2SO4 carrier stream containing 0.1 mol L(-1) (NH4)2SO4, merged with a permanganate solution (8 x 10(-4) mol L(-1)) and passed through a 250 cm FEP (fluoroethylene polymer) photo-reaction coil wound around a 15 W UV lamp. The sample throughput was 30 h(-1), with an LOD (blank plus 3sigma) of 0.5 mg COD L(-1) and a linear range of 0.5-50 mg COD L(-1) (D-glucose, r2 = 0.9966). The method had good precision with relative standard deviations of 2.7% at 5 mg COD L(-1) and 1.2% at 20 mg COD L(-1) (n = 12) for glucose. Results for a COD certified reference material (QC Demand Quality Control Standard) were in good agreement with the certified COD value. Recovery from Tamar River water samples for all three COD standards was 83.0-111.0% and the COD values determined were in good agreement with those of a permanganate index reference method.     

Functional tetrahydroquinoxalines from perfluoroaromatic precursors

A short series of bromo- and nitro-polyfluorobenzene derivatives gave the corresponding tetrahydroquinoxaline systems upon reaction with N,N′-dimethylethylene diamine. This annelation strategy gives useful quantities of functionalised tetrahydroquinoxaline systems which may be interesting scaffolds for the drug discovery arena.     

Application and limitations on thermal and spectroscopic methods for shelf-life prediction

In medical products, shelf-life after thermoplastic processing and sterilization is important, and ionizing radiation has become a preferred sterilization mode for medical devices. We have employed successfully thermal analytical methods to predict shelf-life for many polyolefin materials. However, as the material of construction becoming more sophisticated: multiphase alloys and blends, multi-layer constructions etc., issues existed that require clarification as to what extent these methodologies are applicable. We have employed thermal analytical methods in conjunction with spectroscopic and morphological methods to study the applicability and limitation of these techniques. Results were combined with real life and simulated aging experiments and presented in this article.     

TDDFT studies of electronic structure and first hyperpolarizability of terta-nuclear cubane-like transition metal clusters

The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo; X=S, O, Cl, Se, Br) makes contribution to the optical nonlinearity. It is possible to enhance the hyperpolarizability by substituting the ligands of the clusters.     

On the Intermittency in Nuclear Fragmentations

A simple Monte Carlo simulation and even a partition method can be used to reproduce quite well the power law behavior between the factorial moment and the charge interval of fragment charge distributions from the multifragmentation of ¹⁹⁷Au nucleus bombarding emulsion at～1 GeV/nucleon. This indicates that the above power law seems not to be a unique precursor of the intermittent behavior in nuclear multifragmentations.     

NUCLEAR CHARGE DISPERSION OF FRAGMENTS IN HIGH ENERGY PROTON-NUCLEUS COLLISION

The charge dispersion of fragments in high energy p+Cu,Kr and Xe reactions are calculated by statistical model and Monte Carlo technique.The corresponding data are reproduced quite well.It is shown that the charge dispersions are all nearly gaussian.The mass dependence of the most probable fragment charge reflects the rest target memory effect.     

EQUATION OF STATE OF HOT NUCLEI BEFORE BREAK-UP

Following the method developed by the authors,recently,the equation of state of hot nuclei(²³⁸U in concrete) before break-up was investigated numerically.The isotherms are drawn in the plan of the general pressure P versus volume V_RT. They are similar to those of Van der Waals gas.The critical temperature of phase transition should correspond to the isotherm with one turning point only.It turns out that the data of mass yield distribution can be reproduced by many pairs of parameters T and V_RT (freeze-out temperature and freeze-out volume) varying in certain range.For each isotherm (each T),the data are always best reproduced by the value of V_RT located at the maximum general pressure within two phases coexistence region.     

Λ Production and Λ/p Ratio in Relativistic Heavy Ion Collisions

The Λ multiplicity and Λ/p ratio are studied by hadron transportation-string fragmentation model in relativistic heavy ion collisions. Firstly, the dependence of Λ multiplicity and Λ/p ratio on the system size and the collision centrality is studied. It shows that the Λ and p multiplicities go up as the increase of system size and the increase of collision centrality. However, their ratio keeps almost a constant. The effect of Λ annihilation cross section to Λ multiplicity and Λ/p ratio is also studied. It is found that this effect is weak: Λ multiplicity and Λ/p ratio have a little amount of increase by the decrease of Λ annihilation cross section. Even the cross section is down to zero, Λ/p ratio is only 1.2 in 200A GeV AuAu head on collision. The Λ/p ratio is obtained to be 0.28 in pp collision, lying in the range of experimental data:0.2—0.3. It is also obtained that the ratio in AA collisions is 3—5 times of that in pp collision.     

Variations in the strength of the infrared forbidden 2328.2 cm-1 fundamental of solid N2 in binary mixtures.

We present the 2335-2325 cm-1 infrared spectra and band positions, profiles and strengths (A values) of solid nitrogen and binary mixtures of N2 with other molecules at 12 K. The data demonstrate that the strength of the infrared forbidden N2 fundamental near 2328 cm-1 is moderately enhanced in the presence of NH3, strongly enhanced in the presence of H2O and very strongly enhanced (by over a factor of 1000) in the presence of CO2, but is not significantly affected by CO, CH4, or O2. The mechanisms for the enhancements in N2-NH3 and N2-H2O mixtures are fundamentally different from those proposed for N2-CO2 mixtures. In the first case, interactions involving hydrogen-bonding are likely the cause. In the latter, a resonant exchange between the N2 stretching fundamental and the 18O = 12C asymmetric stretch of 18O12C16O is indicated. The implications of these results for several astrophysical issues are briefly discussed.