Absolute Rates of Recombination and Disproportination of Dimethylaminyl Radicals

Article abstract of DOI:10.1021/j100138a012

The absolute rate constants for the recombination (k_r) and disproportionation (k_d) reactions of dimethylaminyl radicals were determined at room temperature with the very low pressure reactor (VLPR) technique.The obtained values were k_r = (1.70 +/- 0.19) x 1E-12 cm³ molecule^-1 s^-1 and k_d = (4.19 +/- 0.52) x 1E-12 cm³ molecule^-1 s^-1, and the ratio k_d/k_r was 2.32 +/- 0.26.The transition-state geometries for both recombination and disproportination reactions are loose, with the N...N bond length ca. 3.5 Angstroem and the N...H...C distance ca. 4.4 Angstroem.In the recombination TS, the four C-N...N bending modes are ca. 90 cm^-1 and play a significant role in the formation of the N-N bond in tetramethylhydrazine.In the disproportionation TS, the two (in-plane and out-of-plane) vibrational modes of the metathetic hydrogen are ca. 110 cm^-1 and are essential in the formation of the N-H bond in dimethylamine.