Table 1.

Substituents, their corresponding Hammett constants (σ_p), and the classifications used in the current study. Negative values correspond to electron donating substituents and positive values correspond to electron withdrawing substituents.

Substituent	σp	Classification
N(CH3)2	−0.83 a	Donating
OCH3	−0.27 a
F	0.06 a	Withdrawing
Cl	0.23 a
Br	0.23 a
COOH	0.45 a
CF3	0.54 a
SO3H	0.64 b
CN	0.66 a
NO2	0.78 a

^a Values taken from Hansch et al. [55]. ^b Values taken from Imaizumi et al. [56].