It is still true that chemical reactions can be explained by a quantum treatment of the electrons and a classical motion of the nuclei. The paper tries to make this finding more plausible by examining elementary ground and excited state reactions using Car-Parrinello and Born-Oppenheimer molecular dynamics. Several different reaction pathways leading to different products were observed for the chlor methane photoreaction, illustrating the classical chaos connected with molecular dynamics on-the-fly simulations. Kasha's rule saying that all photochemistry occurs in the first excited state is preserved one more time.