During curation of the azide dataset, it became apparent that acyl azides possess Tdec values that are categorically lower than the Tdec of azides attached to other functionalities. The best Tdec model generated (vide infra for modeling workflow) for the full azide dataset (N = 34, R 2 = 0.75, Q 2 = 0.69) contained an appreciable univariate correlation (R 2 = 0.47) between Tdec and the σ*(C-N3) occupancy descriptor (Figure ). For the full azide dataset, the correlation coefficient corresponding to this plot is given as -0.69; however, upon removal of the nine acyl, iminyl, and peroxyl azides, this correlation coefficient is given as +0.68. This categorical difference is easily visualized in Figure and carries an intuitive interpretation. In analogy to a concave upward nonlinear Hammett plot, this indicates that these azides follow a different decomposition mechanism than the remainder of the azide HEMs. This finding is in agreement with the literature, as acyl azides can readily undergo a Curtius rearrangement to furnish the corresponding isocyanate with the liberation of molecular nitrogen. This concerted reaction mechanism is not accessible to other classes of azides, which most likely decompose via transient nitrene species and the liberation of molecular nitrogen. As such, models generated including these azides are a useful tool in mechanistic classification but fail to provide the detailed chemical interpretability we desired. This mechanistic divergence prompted us to exclude the nine acyl, peroxo, and iminyl azides in our dataset from further Tdec modeling efforts.