The preceding case studies focused on model reaction performance across different chemistries and reaction mechanisms. However, in many applications, the chemical and reaction space is much narrower and this may enable relatively simple corrections to be applied to the model reaction activation energy estimates. Alkane pyrolysis was used as a benchmark for a relatively closed system of reactions to investigate the feasibility of using systematic corrections to the model reaction energies. The possible reactions in the alkane pyrolysis system were graphically enumerated following four elementary reactions, namely radical initiation (homolytic C-C bond cleavage), hydrogen abstraction, alkyl decomposition (C-C β-scission) and alkyl recombination (Fig. ). The activation energies of radical initiation reactions can be approximated by the bond dissociation enthalpy computed by the alfabet package. Meanwhile, the alkyl recombination reactions can be treated as barrierless. For the remaining two types of reactions, the model reaction concept was utilized to efficiently predict the activation energies. In total, 45 and 14 model reactions are generated for radical decomposition and hydrogen abstraction reactions, respectively. To benchmark the deviation between actual and model reactions, 50 reactions are collected for each model reaction, except for 2 radical decomposition and 2 hydrogen abstraction reactions where the model reaction itself is the only reaction of that class (MR 48, MR 52, MR 54, and MR 59 in Fig. ). Starting with the smallest reactions for a particular model reaction, the complexity of reactants were successively increased by exhaustively adding methyl groups while freezing the reacting centers until 50 reactions were sampled. Up to 3 TS initial guesses were generated for each reaction based on the corresponding TSs of model reaction and the conformational sampling strategy 3 (SSIII). After optimizing and verifying these TS initial guesses, 2644 activation energies of actual reactions were obtained to be compared with 55 activation energies of model reactions which represent a intended rate of over 96%. The activation energies were all computed at the ωB97XD/def2-TZVP level of theory. The enthalpies of reaction (∆H r ) were computed by TCIT for these actual reactions to study the relationship between activation energies and enthalpies of reaction. The deviation of the activation energy for each model reaction is calculated separately (Fig. ). The mean absolute error (MAE) of 32 out of 55 model reactions is less than 1 kcal/mol, which means that chemical accuracy is effectively reached without any additional corrections.