Reactions of aryl diazonium salts and arylazo alkyl ethers. VI. A comparison of the available methods for the measurement of the rate of ionization of (Z)-arylazo alkyl ethers in alcoholic solvents

Abstract

Two previously reported methods for the determination of the ionization rate of (Z)-arylazo alkyl ethers by using x-naphtholate ions as a trapping agent are compared. A new method, which uses thiophenolate ions to trap the free diazonium ions formed in this ionization, is reported. This method is recommended in preference to the earlier methods because it includes a correction for the effect of the ionic strength of the solution on the rate of ionization. Rates measured by the thiophenolate method are consequently lower than those measured by either of the two previous methods. The advantages and disadvantages of the new method are discussed. The magnitude of salt effects and substituent effects on the ionization of (Z)- and (E)-arylazo alkyl ethers are compared.