| The work described in this thesis deal primarily with the ortho-quinone present in high-yield pulp. In the first part of this thesis a sensitive fluorescence method is described using derivatized pyrene compounds, as well as other, more red-emitting fluorescent molecules to detect ortho-quinone structural moieties in high-yield pulp and paper. This method is selective, efficient, and by means of time resolved diffuse reflectance fluorescent spectroscopy and fluorescent microscopy, it is possible to show that, during photoyellowing of high-yield pulp, ortho-quinoid groups form in domains. Furthermore, fluorescence microscopy made it possible to determine that the morphological structures of the high yield pulp, where the quinone formation occurs preferentially, are the fines, broken fibers and aggregates.;The second part of this thesis deals with ortho-quinone formation via multiphotonic processes involving phenoxy radicals. To study multiphotonic processes, laser drop photolysis and two-laser two-color techniques were used. For detection, products were derivatized, and examined by means of fluorescence spectroscopy and a gas chromatograph with mass spectroscopy as detection system (GC-MS). The process was shown to have a very low quantum-yield.;The third part of the thesis describes the photochemistry of 1,3-dichloro-1,3-diphenylpropanes. In polar solvents, beside the expected monophotonic processes, high-intensity irradiation light leads to the formation of 1,3-diphenylallyl radicals. In polar solvents, only monophotonic reactions were observed. Further, the 1,3-diphenylallyl cation was also detected. To explain the kinetics of the formation of this cation, a four member cyclic chloronium cation was suggested as a precursor. Both the precursor and the allyl cation were characterized by their quenching with a number of nucleophiles and anions. Irradiation of the 1,3-diphenylallyl cation leads to the appearance of a new transient which was suggested to be its Z-isomer. |
