A pruning procedure was used to assemble effective reaction networks and accurate half-lives for each alkane (Fig. ). The size of the untruncated pyrolysis network grows exponentially with respect to size, making the direct simulation out to terminal products impractical. For example, the reaction network of n-C 15 H 32 is composed of over a billion reactions. However, the downstream reactions from the parent alkane have little impact on the half-life, which allows these networks to be pruned depth-wise based on their simulated flux while retaining an accurate half-life calculation (See Section 1.3 of SI). The network pruning approach was benchmarked against complete reaction networks for all structural isomers of alkanes from ethane through decane (i.e., the 149 systems for which complete simulations out to terminal products were practical). Using a minimum relative flux threshold of 10 -9 , a robust fit was observed (Fig. ) with a reduction of up to 10 8 times in terms of the number of unique reactions required to include in the reaction network while still obtaining an accurate half-life (Fig. ). The growth of unique reactions vs. alkane length also drops to a linear trend compared to the exponential trend for complete networks. The distribution of ERS in pruned reaction networks exhibit a drastic reduction in H-abstraction reactions (Fig. ).