Fig. 2: Yield distributions over the reaction spaces of E1 and S_N1 reactions.

a,b, Schemes of E1 (a) and S_N1 (b) reactions and their mechanisms. For the former, we use 9-butyl-9H-fluoren-9-ol substrate 13a and for the latter, to prevent elimination, 9-phenyl-9H-fluoren-9-ol 14a. For E1, the parameters of the mechanism are the temperature dependences of equilibrium constant K_α for dynamic equilibrium between 13a and its protonated form, of equilibrium constant K_β for dynamic equilibrium between 13b and its protonated form, of pK_a of HBr in acetonitrile and the Eyring–Polanyi equation parameters for kinetic rate constants k_E1 and k_−E1 for water molecule elimination from the protonated 13a (Supplementary Information Section 5.2). For S_N1 at a given temperature, the only parameter is the effective equilibrium constant K_SN1 = [14b][H₂O]/([14a][HBr]) (Supplementary Information Section 5.1). E1 used acetonitrile as solvent. For S_N1, the solvent was dioxane with admixture of AcOH (to homogenize the biphasic dioxane–water mixture formed in situ and complicating optical detection). c,d, Corresponding yield distributions of products 13b and 14b. For clarity, only 125 conditions per cube are shown. Marker colours and sizes are proportional to yields. Yield colour scales are the same for both cubes. Surfaces of equal yield are at 20%, 40%, 70% and 85%. e,f, Kinetics model (curves) fitted to experimental yields with respect to alcohol (circles) for E1 and S_N1 reactions. To better visualize the quality of fits, only two-dimensional snapshots of the entire dataset are shown, here T = 21 °C for E1 and T = 36 °C for S_N1 (for similar plots at all temperatures, see Supplementary Information Sections 5.1 and 5.2). Horizontal axis has the initial concentrations of HBr, with the colour corresponding to different initial concentrations of the alcohol indicated in the keys.