must approach zero, with lim ∆𝐸 𝑟 →-∞ Δ𝐸 ‡ (𝐸 r ) = 𝐸 𝑝𝑟𝑒𝑜𝑟𝑔 , where 𝐸 𝑝𝑟𝑒𝑜𝑟𝑔 represents the ΔEr-independent minimum barrier to be overcome regardless of driving force. The gradient of the non-linear relationship transitions between its limits at 0 and 1, which constitute horizontal asymptotes. For an idealised reaction following Hammond's postulate, and so in which the geometry of the TS is fully and exclusively defined by its connected minima, only the factors influencing the TS are present to various degrees in the connected minima, and so the response of ΔE ‡ must vary with the energetic proximity to the minima. As the position of the energy barrier stems from an interpolation of stabilising factors that change monotonically in elementary processes, the response of ΔE ‡ thereto must be of the same sign as the response of ΔEr. In cases where this does not hold, the TS cannot be seen as an interpolation of factors, which only occurs if the potential energy surface shows extensive asynchronicity, caldera-like regions or bifurcation-like behaviour. 14 These effects of asynchronicity can lead to incorporation of extraneous stabilisation factors, as one of the minima would be less geometrically related to the TS, and presumably significant changes in reaction energy unrelated to the factors affecting the barrier. Only in this scenario, perhaps closer in nature to a collection of independent steps than to a concerted process, would the TS correlate weakly enough for monotonicity not to be preserved: this can lead to cases where local observed Brønsted slopes were negative or higher than 1, a few examples of which have been presented as outliers in the literature. Therefore, for any single synchronous elementary process,