PubMed · 14042500
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
E GRANDJEAN. PYRIDINE.. https://doi.org/10.1080/00028896309343242
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
A new proposal of vibrational assignment for pyridine is reported. Infrared spectra for the liquid and gas phases as well as Raman spectra for the liquid have been recorded and analyzed for -d(0), -d(5) and, for the first time to our knowledge, for 15N isotopomers as well. The proposal of assignment has been assessed by the calculation of a number of force fields, theoretical (ab initio, density functional theory) approaches as well as by a set of simple valence internal coordinates force constants transferred from benzene using the pure vibrational force field approximation. In all cases, the root mean square (rms) for the wavenumbers turn out to be lower than the best obtained so far, i.e. 6.6 cm(-1), as stated by Wiberg et al.
With the aim to qualifying and quantifying the acidity of the Y, L and ferrierite zeolites, an infrared band analysis of pyridine adsorption and programmed temperature dessorption measurements were carried out to a set of nine samples of the Y, L and ferrierite zeolites. The infrared spectra before and after the pyridine adsorption process had revealed that the ferrierite zeolite shows, almost in the totality, Brönsted acid sites. The Y and L zeolites present, also, significative concentrations of Brönsted and Lewis acid sites. These facts allow to conclude that zeolite ferrierite is the strongest acid zeolite among these three types.
The ultraviolet absorption spectrum in the range 340-185 nm in the vapour and solution phase has been measured for 2-fluoro-5-bromopyridine. Three fairly intense band systems identified as the pi* <-- pi transitions II, III and IV have been observed. A detailed vibronic analysis of the vapor and solution spectra is presented. The first system of bands is resolved into about sixty-two distinct vibronic bands in the vapour-phase spectrum. The 0,0 band is located at 35944 cm(-1). Two well-developed progressions, in which the excited state frequencies nu'25 (283 cm(-1)) and nu'19 (550 cm(-1)) are excited by several quanta, have been observed. The corresponding excited state vibrational and anharmonicity constants are found to be omega'i = 292 cm(-1), x'ii = 4.5 cm(-1) (i = 25) and omega'i = 563.8 cm(-1), x'ii = 6.9 cm(-1) (i = 19). The other two band systems show no vibronic structure, the band maxima being located at 48346 and 52701 cm(-1), respectively. The oscillator strength of the band systems in different solutions and the excited state dipole moments associated with the first two transitions have been determined by the solvent-shift method. The infrared spectrum in the region 4000-130 cm(-1) and the laser Raman spectrum of the molecule in the liquid state have been measured and a complete vibrational assignment of the observed frequencies is given. A correlation of the ground and excited state fundamental frequencies observed in the UV absorption spectrum with the Raman or infrared frequencies is presented.