A major thrust of this paper is the use of phonon spectroscopy to investigate the dynamics of reactions in solids. The information on optical phonon spectra is obtained by laser Raman investigation in the low frequency region (10-200 cm** minus **1). A clear example of the application of Raman phonon spectra in understanding the lattice rearrangement is provided by the photopolymerization of 2,5-distyrylpyrazine in the solid state alpha -form. A stepwise photoreaction was used to stabilize an intermediate oligomer structure. For this purpose, the 476. 5 nm argon-ion laser line was used to convert the monomer to the oligomer. Then further photoreaction of the oligomer to produce the polymer was carried out with the 355 or 417 nm laser line from a Nd:Yag laser system.