Aromatic hydrocarbons constant monitoring

While various techniques, such as stopped flow, have been used to follow substrate kinetics, many kinetic measurements have involved the photophysical properties of solubilized probes. Because of the luminescent properties of their excited states, the aromatic hydrocarbons provide opportunities for monitoring movement of such probes across the micelle boundary. For example, long-lived phosphorescence of aromatic hydrocarbons has been monitored in micellar solutions containing ionic quenchers that themselves are repelled by the surfactant head groups. Since quenching must take place in the aqueous phase, phosphorescence lifetimes may be interpreted to provide rate constants for exit of the probe from the micelle. Some typical values obtained by this technique are given in Table III. Fluorescence data have also been used to obtain such information. 

N.M.R. Spectroscopy. For comparing mixtiires of saturated hydrocarbons from different fuels and for monitoring the effectiveness of silica-gel column chromatography in the separation of normal alkanes from non-normals by 100 and, especially, 220 MHz H N.M.R., the emphasis is on the chemical-shift profile (j 0) and peak areas rather than on spin-spin coupling constants (Table III). Although the 100 MHz spectra indicate that the n-hexane-soluble part of Montan wax in CCli has rather similar hydrogen distributions to the chloroform-soluble part,about of Montan wax was soluble in n-hexane presumably the n-hexane-insoluble fraction contains all the alkanes, as well as polycyclic aromatics. The spectra of n-hexane- and chloroform-soluble fractions of Turkish asphaltite indicate hydrogen distributions of about 7.8 and 12.2 Hy, 21.2 and 22.0 H, U6.0 and U3.3 Hg, and 25 and 22.5/ Hy. 

---