Comparison of the mechanisms of the thermal decompositions of 2,2′-azisobutane and azoisopropane

Abstract

The gas phase pyrolyses of 2,2′-azoisobutane and azoisopropane have been investigated in the temperature range 471–573 K. The products of 2,2′-azoisobutane (AIB) decomposition result from the following elementary reactions. AIB [graphic omitted] 2t-C4H9+ N2(1), 2t-C4H9 [graphic omitted] iC4H10+ iC4H8(2), 2t-C4H4 [graphic omitted] 2,2,3,3-tetramethylbutane (3)

The disproportionation-combination rate constant ratio, kd/kc, for t-butyl radicals has been determined as 2.60 ± 0.04 in the temperature range 483 to 515 K.

In addition to the corresponding reactions (1) to (3) involving isopropyl radicals, azoisopropane (AIP) decomposition involves the abstraction reaction, iC3H7+ AIP [graphic omitted] C3H8+ AIP (4). In the temperature range, 518–573 K, ka is given by the expression, log10ka/(kc)½/cm[fraction three-over-two] mol–½ s–½= 5.26 ± 0.22 –(41.64 ± 2.31) kJ mol–1//2.303 RT, and the disproportionation-combination rate constant ratio for isopropyl radicals has been found to fall from 0.52 at 518 K to 0.49 at 573 K.