Synthesis and Thermal Decomposition of CIS-3,4,5,6-Tetrahydropyridazine-3,4-d₂

Chapter I The stereospecific syntheses of cis-tetrahydropyridazine- 3,4-d2 (6) and cis- and trans-cyclobutane-1,2-d2 are reported. The thermal decomposition of cis-tetrahydropyridazine-3,4- d2 (6) (gas phase, 439°) affords 67.1 ± 0.9% cis-ethylenel, 2-d2, 16.1 ± 0.8% trans-ethylene-1,2-d2, 9.4 ± 0.4% ciscyclobutane- 1,2-d2, 7.4 ± 0.4% trans-cyclobutane-1,2-d2. The relative rates of rotation, cleavage, and closure for this 1,2-diazene generated tetramethylene-d2 are k(cleavage)/k(closure) = 2.2 ± 0.2 and k(rotation)/ k(closure = 12 ± 3. An extra stereospecific cleavage component (46%) superimposed on the 1,4-biradical pathway (54%) from the parent tetrahydropyridazine was found, similar to that observed in the 3,4-dimethyl-3,4,5,6-tetrahydropyridazine thermal reactions. Finally, the experimental data for the parent 1,4-biradical, tetramethylene, are compared to calculated values in the literature. Chapter II The gas phase pyrolysis of 3,3,4,4-tetramethyldiazetine has been performed in the inlet system of a photoelectron spectrometer. By analysis of the observed internal energy content of the nascent nitrogen and 2,3-dimethyl-2-butene products, estimates on the limits of the amount of reaction exothermicity released to vibration of the nitrogen fragment could be made. It appears that nitrogen acquires very little of the available energy and the implications of this result are discussed in terms of a model which has been proposed for distinguishing concerted and stepwise decomposition of azo compounds.