Spectroscopy ultra violet

Raman spectroscopy has been utilized in the quant detn of nitramines and nitrosamines (Vol 1, A177-R Ref 61), and ultra-violet spectroscopy is employed for the quant measurement of TNT in HBX compn (Refs 39, 61 63)... 

Jorgensen CK (1969) Valence-Shell Expansion Studied by Ultra-violet Spectroscopy. 6 94-... 

The conventional approach to solvent extraction is the batch method. Early work with this method was hampered by the low concentration of the compounds present and the relative insensitivity of the methods of characterization. Thus lipids and hydrocarbons have been separated from seawater by extraction with petroleum ether and ethyl acetate. The fractionation techniques include column and thin-layer chromatography with final characterisation by thin-layer chromatography, infrared, and ultra-violet spectroscopy and gas chromatography. Of these techniques, only gas chromatography is really useful at levels of organic matter present in seawater. With techniques available today such as glass capillary gas chromatography and mass spectrometry, much more information could be extracted from such samples [20]. 

Infra-red, microwave, and X-ray photoelectron spectroscopy Infra-red and ultra-violet spectroscopy has been widely used for investigating the structure of intermolecularly hydrogen-bonded complexes in the solid state (Novak, 1974) and in solution (Zundel, 1976, 1978 Clements et al., 1971a,b,c Pawlak et al., 1984). By analysing the infra-red spectra of equimolar liquid mixtures of amines with formic or acetic acid, the relative importance of structures [10] and [11] was estimated (Lindemann and Zundel, 1977). It was proposed that [10] and [11] make equal contributions to the observed structure of the complex when the p -value of the carboxylic acid is approximately two units lower than that of the protonated amine. 

Structural information at the molecular level can be extracted using a number of experimental techniques which include, but are not restricted to, optical rotation, infra-red and ultra-violet spectroscopy, nuclear magnetic resonance in the solid state and in solution, diffraction using electrons, neutrons or x-rays. Not all of them, however, are capable of yielding structural details to the same desirable extent. By far, experience shows that x-ray fiber diffraction (2), in conjunction with computer model building, is the most powerful tool which enables to establish the spatial arrangement of atoms in polymer molecules. 

Valence-Shell Expansion Studied by Ultra-violet Spectroscopy... 

Seen from the point of view of ultra-violet spectroscopy, the situation of aromatic P-, S-, As- and Se-compounds is far more indeterminate than in the t5q)ical oxo and fluoro complexes of the same elements in high oxidation states. Thus, gaseous SFs does not have absorption bands before 95 kK 64) and it is by no means certain that the excited states of these bands involve 3d-orbitals. In many ways, it looks much more as a 4s-like Rydberg state of the whole molecule. 

Kinetic study of the propagation reaction by ultra violet spectroscopy. 

The initiation step is followed by ultra violet spectroscopy at 273 nm (polyisoprenyllithium absorption). The following experimental conditions are choosen temperature 18 °C t-BuLi = 4 x lO mole.l 1... 

After 4 or 5 hours the reaction is complete and a sigmoidal living ends formation curve is observed (1 ). The degree of polymerization of the oligoisoprenyllithium equals about ten. By addition of catalytic amounts of complexing agent (TMEDA or PMDT) the remarkable increase of the initiation rate is not measurable by ultra violet spectroscopy. Also, only the propagation step was studied. 

The purification of chemicals, the synthesis and the study of the living species using protonic nuclear magnetic resonance and ultra violet spectroscopy have been intensively described in other papers (18, 19). 

All the experiments were carried out at 18 C under high vacuum (10 mm of mercury) in sealed glass vessel supplied with an ultra-violet cell. Before polymerization the apparatus is care -fully and successively washed with a cyclohexane solution of butyllithium and cyclohexane. The stability of complexed poly-isoprenyllithium has been verified by protonic nuclear magnetic resonance and ultra violet spectroscopy (18)... 

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