Anew and improved synthesis cis, syn-o,o'-dibenzene 1 was developed to obtain 1 in larger amounts with improved purity, syn-Dibenzene 1 undergoes thermolysis to two molecules of benzene at a rate slower than that of the thermodynamically more stable anti-dibenzene 2. Kinetic analysis revealed that the higher thermal stability of 1 is due to the higher heat of activation in thermolysis. Photoelectron spectroscopy of 1 showed that the through-bond interaction between the two cyclohexadiene units in o,o'-dibenzenes is more important than their through-space interaction. A comparative study on the thermolyses of related syn-o,o'arene:benzene dimers suggests that thermolyses of syn-o,o'-arene:benzene dimers proceed via their anti-isomers as an intermediate. syn-Dibenzene 1 also undergoes adiabatic photolysis to one molecule of excited benzene and one molecule of ground-state benzene in goad efficiency. The mechanisms of these reactions an discussed.