Chemical transformations in the dense fluid phase studied by high-pressure spectroscopy

4 Chemical transformations in the dense fluid phase studied by high-pressure spectroscopy 

Experimental IR absorbance spectra, measured during the cycloaddition of 1 and 3 in CH2CI2 solution at 60 °C and 1500 bar, are shown in Fig. 6.7-16. Absorptions attributed to the solvent and to vibrational modes, which do not change during the reaction, are easily eliminated by subtracting the first spectrum, which is recorded after the system has reached the experimental temperature and pressure, from all subsequently measured spectra. The spectra shown in Fig. 6.7-16 are thus transformed into the spectroscopic data 

Diels-Alder reactions have also been studied via the fundamental and the first overtone absorptions of carbonyl stretching modes. Absorbance spectra measured during the cycloaddition of 2 (with R = CCI3) and 3 in CH2CI2 solution at 1000 bar and 95 °C are shown in Fig. 6.7-18. 

In addition to time-dependent experiments, the ratio at which the diastereomeric products 6 and 7 are formed as a function of the reaction pressure and temperature has been studied by high-pressure liquid chromatography. The chromatographic analysis was per- 

Application of high-pressure vibrational spectroscopy in order to study and to monitor technically relevant fluid phase processes under extreme conditions is exemplified by high-pressure ethene polymerization. Several vibrational bands in the IR and the NIR may be used to detect concentrations directly in the ethene/polyethylene system (Buback, 1984). Some of these are plotted in Fig. 6.7-20. The conversion of unsaturated (ethylenic) 

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