New cross section functions for hot 18F atom collisions with H2, HD and D2

New analytic reaction cross-section functions are reported for hot ¹⁸F atoms reacting with H₂, HD and D₂. A realistic model is proposed for the total non-reactive cross section in these systems throughout the center-of-mass collision energy range 0–100 eV.     

4,4-Dimethoxybutan-2-one in the synthesis of 4-nitrosopyrazoles

Russian Journal of Organic Chemistry -     

Adsorption and reaction of nitric oxide and oxygen on Rh(111)

Adsorption of NO and O₂ on Rh(111) has been studied by TPD and XPS. Both gases adsorb molecularly at 120 K. At low coverages (θ_NO < 0.3) NO dissociates completely upon heating to form N₂ and O₂ which have peak desorption temperatures at 710 and 1310 K., respectively. At higher NO coverages NO desorbs at 455 K and a new N₂ state obeying first order kinetics appears at 470 K. At saturation, 55% of the adsorbed NO decomposes. Preadsorbed oxygen inhibits NO decomposition and produces new N₂ and NO desorption states, both at 400 K. The saturation coverage of NO on Rh(111) is approximately 0.67 of the surface atom density. Oxygen on Rh(111) has two strongly bound states with peak temperatures of 840 and 1125 K with a saturation coverage ratio of 1:2. Desorption parameters for the 1125 peak vary strongly with coverage and, assuming second-order kinetics, yield an activation energy of $\text{85 ± 5}\text{kcal}\text{mol}$ and a pre-exponential factor of 2.0 cm² s^?1 in the limit of zero coverage. A molecular state desorbing at 150 K and the 840 K state fill concurrently. The saturation coverage of atomic oxygen on Rh(111) is approximately 0.83 times the surface atom density. The behavior of NO on Rh and Pt low index planes is compared.     

Vibrational spectra of high- and low-density amorphous ice,ice Ic,and ice Ih by neutron scattering

Abstract

The vibrational spectra of high- and low-density amorphous ice made ice Ic and Ice Ih have been obtained at 15 K using inelastic incoherent neutron scattering     

The rise of energy accumulated in metal nanopowders

The influence of nanopowder irradiation by fast (4-MeV) electrons on the energy stored in nanopowders is studied. It is found that the irradiation of the nanopowders increases the amount of accumulated energy by 2.5 times as a maximum compared with the thermal effect of nonirradiated nanopowder oxidation.     

F-to-HF reactions. VIII. Nonthermal complications for the CHF3/C3F6/C2F6 moderated nuclear recoil system

Results are reported from moderated nuclear recoil ¹⁸F experiments with the 273 K CHF₃/C₃F₆/C₂F₆ system. Although the measurement sensitivity is only about ±12%, there is no evidence to support the occurrence of nonthermal F-to-HF reactions at 95 mol % C₂F₆ moderator concentration.     

Effect of the conditions of anodizing on the morphology of nanotitania

The effect the current density, treatment time, surface pretreatment, and electrolyte composition have on the morphology of titania obtained via electrochemical treatment in such ionic liquids (ILs) as 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][NTf₂] and 1-butyl-3-methylimidazolium chloride [BMIM]Cl is studied. The anodic formation of titania nanostructures in the form of nanotubes or nanorods is found to occur in times of up to 100 s. The role of water in the formation of these titania nanostructures is shown. Pretreatment has no effect on the morphology of the formed oxide. The formation of products that are poorly soluble in ILs (e.g., hydrated oxides) results in the emergence of a layer partially covering the open parts of nanotubes, preventing their further growth.     

Analysis of the compounds in the synthesis mixtures of hydroxy acids by a gradient programmed RP-HPLC with UV/vis and RI detectors

Summary A gradient programmed reversed phase high-performance liquid chromatographic (RP-HPLC) method is described for the quantitative determination of some aldehydes, hydroxy aldehydes, unsaturated aldehydes, hydroxy carboxylic acids, carboxylic acids, alcohols and polyols using an ultraviolet and a refractive index detector in series. The sample matrices are synthesis mixtures of hydroxy carboxylic acids. The structures of the hydroxy aldehyde intermediates are determined by¹³C NMR and the influence of sample preparation on analysis results is discussed. The limits of detection and the precision of the method are evaluated.     

Preparation, characterization and application of a stationary chromatographic phase from a new (+)-tartaric acid derivative

The preparation, characterization and application of a new stationary phase derived from 1,4-cyclohexanedione and diethyl (+)-tartrate are described. A suitable TADDOL for immobilization has been synthesized and grafted to a γ-mercaptopropylsilylated silica gel. The resulting modified stationary phase has been characterized and its ability to separate enantiomers has been studied. While the free TADDOL in solution was able to resolve a range of enantiomers, the resolving properties were lost on immobilization. Solid state ¹³C CPMAS NMR of the new stationary phase was used to explain the lack of stereoselective recognition.