Table 2.

Relative energies (kJ·mol⁻¹) of protonated species 1–5 and their corresponding anions 8–12, relative to 1-napthol (6), calculated with the M06-2X DFT method. Mean standard error (MSE) for mixed systems with M06-2X/6-31+G(d,p) has been reported as −1.0 kJ·mol⁻¹ [35].

Species	H-in (a)		H-out (b)a	Anionb
	6-31+G(d,p)	6-311+G(3df,2p)		6-31+G(d,p)	6-311+G(3df,2p)
1 (H)	−9.7	−10.2	0	−5.6	−7.5
2 (NO2)	−0.2	−1.6	0	−41.5	−42.6
3 (Cl)	−6.1	−7.1	0	−19.7	−21.3
4 (CH3)	−11.7	−12.3	0	−4.6	−6.4
5 (OCH3)	−11.5	−12.3	0	−3.8	−5.7

All values included zero point corrections, scaled to 0.967 [36]. ^aSet arbitrarily at zero for comparison across each row. Either smaller or more negative numbers denote more stable species. ^bCalculated from the isodesmic reaction with naphthol 6 to afford the corresponding anion, using H-out (b) as the neutral. Larger negative values indicate anions relatively more stable with respect to naphtholate.