Table 6. Sigma constants for various substituents ^a.

Wt% ETOH	ρ	Sigma constants
		m-CH3	P-CH3	m-NH2	p-NH2	m-OH	p-OH	m-Cl	p-Cl	m−NO2**	P−NO2**
0	1.00	−0.07	−0.19	−0.61	−0.74	0.14	−0.32	0.37	0.14	0.72	0.78
16.5	1.17	−0.12	−0.31	−0.42	−0.64	−0.05	−0.42
34.4	1.36	−0.04	−0.11	−0.13	−0.55	0.05	−0.30	0.38		1.13	1.04
44.1	1.46	−0.05	−0.11	−0.13	−0.54	0.02	−0.29	0.36	0.30	0.77	0.88
64.8	1.58	−0.10	−0.08	−0.18	−0.60	−0.08	−0.35	0.33	0.27	0.75	0.85
75.9	1.60	−0.09	−0.08		−0.62	−0.08	−0.39	0.34	0.30	0.71	0.81
87.7	1.61	−0.14	−0.11		−0.66	−0.12	−0.47	0.33	0.26	061	0.77
93.7	1.62									0.82	0.90
100*	1.63	−0.14	−0.14		−0.66	−0.13	−0.48	0.34	0.28	0.86	0.96
Averge		−0.09	−0.14	−0.29	−0.63	−0.03	−0.38	0.35	0.26	0.80	0.87
Estimated standard deviation		0.04	0.08	0.21	0.06	0.0	0.07	0.02	0,06	0.15	0.09

^*From extrapolated pK values.

^**Undirected pK values using quinhydrone electrode for benzoic acid and substitued benzoic acids.

^aCalculated from Bright and Briscoe [13].