A Convenient Method to Obtain 4,5-Dihydro-1H-Methylpyrazoles by A Ring Transformation Reaction

A convenient method for the synthesis of alkyl[aryl]-substituted 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-methylpyrazole (2) from a new ring transformation reaction of alkyl[aryl]-substituted-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-pyrazolethiocarboxyamide (1) with methylhydrazine in THF, and the thermal dehydration of 2, are reported.     

INFRARED SPECTRA OF BROMOFORM AT HIGH PRESSURES

Infrared spectra in the wavenumber ranges 100–1800 and 2700–4800 cm^?1 are reported for bromoform samples in diamond anvil cells at ambient temperature and at pressures up to 10 GPa. The freezing pressure is estimated to be 0.13 ± 0.02 GPa. The spectra appear to evolve smoothly and no major discontinuities are detected. The dependence on pressure of eleven peak wavenumbers (five fundamentals and six combinations) is presented. All modes show small percentage increases in wavenumber over this pressure range, except for the degenerate bend, ν₆, which exhibits a 20% increase, suggesting that the equilibrium Br-C-Br angles may be slightly changing with increasing pressure.     

SHOCK COMPRESSION BEHAVIOR OF BROMOFORM

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Adsorption and photochemistry of multilayer bromoform on ice

The adsorption and photochemistry of bromoform multilayers on and in amorphous solid water (ASW) are studied using reflection absorption infrared spectroscopy (RAIRS), temperature-programmed desorption (TPD), and time-of-flight (TOF) techniques. Regardless of the initial exposure, bromoform resides on top of the ASW layer. No migration of bromoform molecules into the ASW film is observed for adsorption on top of the water layer. UV irradiation at a wavelength of 266 nm results in significant desorption of photochemical fragments, reaction of photochemical products on the surface and light-induced molecular reorganization of the remaining CHBr₃, which is apparent from a comparison of pre- and post-irradiation TPD experiments. The ice-mediated C-C (C₂H₂Br₂) and C-O (CHBrO) photoproducts desorb from both the ASW surface and the Pt surface. The photoproduct C₂H₂Br₄ is formed exclusively from multilayers of CHBr₃ and desorbs only from the Pt surface.     

Local structure and orientational ordering in liquid bromoform

The neutron diffraction data of liquid bromoform (CHBr₃) at 25°C was analysed using the Empirical Potential Structure Refinement technique in combination with H/D isotopic substitution. Compared to liquid chloroform (CHCl₃), CHBr₃ displays more spatially defined intermolecular contacts. A preference for polar stacking with collinear alignment of dipole moments is observed for the most closely approaching CHBr₃ molecules, although to a lesser extent than in chloroform. Consistent with this, and in line with dielectric spectroscopy, the Kirkwood correlation factor from the structural model of CHBr₃ is smaller than that of CHCl₃. The net antiparallel alignment of dipole moments in CHBr₃, as suggested by dielectric spectroscopy, must be due to weak but persistent long-range orientation correlations in CHBr₃, which counteract the local polar stacking.