Mechanism of inhibition by isobutene

When a mixture of neopentane and isobutene is pyrolysed, the primary mechanism of 

The isobutenyl free radical CH2-C(CH3)=CH2 is stabilized by resonance and, consequently, is much less reactive than the neopentyl or the methyl radical. Two consequences result from this  

The new rate laws, which take the reactions (67) to (69) into account, can be established using the global QSSA  

Relationships (70) and (71) can be simplified using the so-called crossed-constants approximation, coming from the kinetic theory of gases  

Tq is the rate of formation of CH, at conversion of C3Hj2 equal to zero, in the absence of C4Hg, whereas r is the rate, still at zero conversion of C3HJ25 but in the presence ofC4Hg. 

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