Determining the mechanism of chemical reactions is one of the cornerstones of chemistry and computational quantum chemistry (QM) has been proven very helpful in this regard. QM is mainly used to test the viability of possible reaction mechanisms proposed by chemists through heuristic rules. Generating the proposed mechanism and verifying it computationally is generally done manually and requires expert knowledge. However, several very promising methodologies have been developed to automate the discovery of reaction mechanisms using QM. ] Following Dewyer et al. these methods can be categorized into four categories: 1) encoding mechanistic steps, 2) generate transition state (TS) guesses, 3) generate intermediates using graph theory, and 4) generate driving coordinates. Recently, quantum chemical meta-dynamics based approaches has emerged as a fifth category. Most of these approaches are rather computationally expensive so they have generally been applied to relatively small molecules with less than ten heavy atoms. As a result, the methods have yet to be widely adopted with the exception of atmospheric and combustion chemistry. In this paper we investigate whether fast semiempirical QM (SQM) methods can be used to decrease the computational requirements for automated reaction mechanism discovery, using two different methods for generating reaction intermediates: a graph-based method by Kim et al. and the meta-dynamics based method by Grimme. In general we are interested in finding all reactions that proceed at measurable rates at room temperature, which translates into barrier heights (activation free energies) of no more than 25-30 kcal/mol. To test the reaction prediction algorithms we choose a thoroughly studied system: 3-hydroperoxypropanal . This system has been studied with multiple TS search algorithms: the freezing string method , the single-ended growing string method (SSM) , the double-ended growing string method (GSM), the heuristic KinBot algorithm, and the single-component artificial force induced reaction method (SC-AFIR) and it is therefore quite likely that all low-barrier reactions have been found. In this study we aim to find the three lowest-barrier reactions, which have barrier heights of 36, 40, and 46 kcal/mol (Figure ). These barriers are higher than the target value of 25-30 kcal/mol, which may mean that some of the cutoffs and hyperparameters used in this study may need to be adjusted in future studies. . The reactions correspond to R37/38, R69, and R53 in their notation.