. 2022 Mar 10;87(7):4580–4589. doi: 10.1021/acs.joc.1c02911

Table 1. Relative Free Energies (kcal mol^–1) for the Regioisomers Depicted in Scheme 5 Calculated at Three Different DFT Levels in Vacuo and in Water.

path	species	PBE0/6-31+G(d,p)		ωB97X-D/6-31+G(d,p)		M06-2X/6-311++G(2d,2p)^a
path	species	in vacuo	in water (PCM)	in vacuo	in water (PCM)	in vacuo	in water (SMD)
1a	I-5	n.d.^b	unstable^c	n.d.^b	unstable^c	n.d.^b	n.d.
1a	I-6	n.d.^b	unstable^d	n.d.^b	unstable^d	n.d.^b	n.d.
1b/2b	II-5	n.d.^b	0.3	n.d.^b	0.8	n.d.^b	2.4
1b/2b	II-6	n.d.^b	0.0	n.d.^b	0.0	n.d.^b	0.0
2a	III-5	3.5	4.5	3.0	4.9	4.3	5.0
2a	III-6	0.0	0.0	0.0	0.0	0.0	0.0
3	IV-5	0.0	0.0	0.0	0.0	0.0	0.0
3	IV-6	6.3	5.2	6.2	4.3	4.8	2.8

At the PBE0/6-31+G(d,p) (in vacuo) or PBE0/6-31+G(d,p), PCM (in water) geometries.

Charged/zwitterionic species were examined only in water.

Most starting structures of the zwitterionic adduct dissociate during optimization; only few minima have been identified. The computed Δ_rG⁰ for the reaction (PBE0 level) is 34.5 kcal mol^–1.

All starting structures examined dissociate during optimization.

Table 1. Relative Free Energies (kcal mol–1) for the Regioisomers Depicted in Scheme 5 Calculated at Three Different DFT Levels in Vacuo and in Water.

Table 1. Relative Free Energies (kcal mol^–1) for the Regioisomers Depicted in Scheme 5 Calculated at Three Different DFT Levels in Vacuo and in Water.