text: The Yukawa–Tsuno equation allows for treatment of both para- and meta- substituents, and it also better correlates data from reactions with high electron demand than the original Hammett equation. However, this equation does not take into account the effects of various solvents on organic reactions. Also, Yukawa and Tsuno note that, even within a group of similar reactions, -values for more electron-withdrawing substituents tend to be higher than predicted—seen as a slight increase in slope on a Yukawa–Tsuno plot—and thus, are not as strongly correlated with the remainder of the data.