Measurement of Quantity of Heat and Thermodynamical Prameters for the Chemiluminescent Cycloreversion specific in the Solid State

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We have investigated a thermally forbidden ring fission or ring opening reaction of biplanemers ([4+4] heterodimers of arenes) 1, lophine peroxides 2 and cyclobuta [b] pyroles 3 which are an energy rich system. The chemiluminescent thermal cycloreversion of 9-anthracenecarboxylic acid-benzene biplanemer and the chemiluminescent multiphoton cycloreversion of anthracene- p-difluoro-benzene biplanemer with Nd-Yag IR laser light gave off chemiluminescent light only in the solid phase. As there has not been any attempt to reveal the determinants in the solid state for the chemiluminescence from thermodynamical view points, this prompted us to collect the thermodynamic parameters by differential scanning calorimetry (DSC). In the cases of 1, two substantial exothermal processes are superimposed for the chemiluminescent crystals, whereas one main exothermal process is observed for a nonchemiluminescent powder sample. The thermodynamic parameters for the thermal cycloreversions were collected. Higher activation energy is characteristic of the chemiluminescent process prepared in the solid phase. Efficient chemiluminescence was observed in the thermal reaction of lophineperoxides 2 in both solid and liquid phases. Virtually same activation energies were obtained. The kinetic and thermochemical study of thermal ring opening reaction of 3,5- and 2,4-di-tert-butyl-3a, 5a-dihydro-3H-cyclobuta- [b] pyroles 3a and 3b to the corresponding di-tert-butyl substituted azepines was performed in the solid state, and provided activation energies 12 kcal/mol and 24 kcal/mol, respectively.