Spectrophotometric Determination of Ionisation Quotients of Hydroxytriazenes and the Effect of Substituents on p Ka Values

Abstract

Hydroxytriazenes are very weak acids. The conventional potentiometric and conductometric method cannot be employed for determining their ionisation constants. However, these compounds show a distinct colour change in acid and alkaline media. Ultra-violet absorption studies of these compounds have been made1. The absorption maximum at 305 mµ of 3-hydroxy-3-methyl-1-phenyltriazene shifts to 335 mµ in an alkaline solution. The following equilibrium possibly exists: (molecular form, absorption peak at 305 mµ) (anion form, absorption peak at 335 mµ) This change in absorption maximum with PH has been used in determining the ionisation constants of fourteen hydroxytriazenes employing Robinson’s spectrophotometric method