Table 1. Energetics for the Spontaneous Hydrolysis of the Aryl Phosphate Monoesters Shown in Figure 3, through Either Substrate- Or Solvent-Assisted Pathways^a.

systems		substrate-assisted pathway				solvent-assisted pathway
		M06-2X		ωB97X-D		M06-2X	ωB97X-D
	pKa	ΔGstep1⧧	ΔGstep2⧧	ΔGstep1⧧	ΔGstep2⧧	ΔG⧧	ΔG⧧
3,5-NO2	6.68	28.3	–	31.5	–	25.9	25.2
4-NO2	7.14	28.8	–	31.7	–	27.1	24.8
3-NO2, 4-Cl	7.78	29.4	25.7	32.3	–	28.7	27.9
3-NO2	8.35	29.6	26.7	34.2	–	29.8	29.2
3,4-Cl	8.63	29.4	26.1	32.6	–	30.6	28.7
3-Cl	9.02	30.0	27.6	34.2	31.1	31.1	31.2
4-Cl	9.38	30.7	29.0	34.9	30.8	32.5	31.3
H	10.0	30.6	29.4	33.7	30.7	33.0	32.5
methyl	15.5	33.1	35.6	35.3	40.1	44.1	43.8

^aIn the case of the substrate-assisted pathway, ΔG_step1^⧧ and ΔG_step2 correspond to the activation free energies of the addition and elimination steps, respectively. In cases where the energy of the elimination step is represented as “–”, the reaction proceeds through a concerted pathway with a single TS. In the case of the solvent-assisted pathway, the reaction also proceeds through a single TS throughout, the activation free energy of which is represented by ΔG^⧧. Frequency calculations were performed at 312 K. A more detailed energy decomposition for each pathway is presented in Tables S2–S5. All energies are presented in kcal·mol^–1 at the SMD-M06-2X/6-311+G(d,p)//SMD-M06-2X/6-31+G(d) and SMD-ωB97X-D/6-311+G(d,p)//SMD-ωB97X-D/6-31+G(d) level of theory relative to the lowest-energy reactant state for the two pathways.