The ionization constants of 2-substituted 4,6-diamino-s-triazines: The applicability to the hammett and taft equations

✍ Scribed by Tatsuo Tashiro

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2002
• Tongue: English
• Weight: 147 KB
• Volume: 39
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570390402

✦ Synopsis

The ionization (or basicity) constants (pK b ) were determined for many 2-substituted 4,6-diamino-s-triazines (I) by means of the electrometric titration. I includes 2-alkoxy or aryloxy-(Ia), 2-alkyl-or 2-aryl-(Ib), and 2-alkylamino-or 2-arylamino-4,6-diamino-s-triazines (Ic). For the series with the same alkyl or aryl group, the order of the basicity was found to be Ic > Ib > Ia.

A study was made of relationships between the pK b values of I, and the substituent constants, σ p, σ m , σ p + , σ m + , σ p o , σ m o , σ I , σ n , and σ*. The Hammett relationships were observed between the pK a values of I, and the substituent constants σ m , (or the combination ones, [0.97σ m + 0.03σ p ] as well as another [0.77σ I + 0.23σ R ]). The Taft relationships were also found between the pK a values of Ia, Ib, and Ic and the constants σ*, respectively. Furthermore, in the case of Ic a linear relationship was observed between the pK a values and Σσ*.