Decomposition of Paraoxon and Parathion by Amines, HOO- and OH- Ions: Reaction Mechanism and Origin of the alpha-Effect

作者：Bae Ae Ri; Lee Jieun; Um Ik Hwan^*

来源：Bulletin of the Korean Chemical Society, 2013, 34(1): 201-206.

DOI：10.5012/bkcs.2013.34.1.201

• Paraoxon
• Parathion
• Concerted mechanism
• Solvent effect
• Polarizability effect

The second-order rate constants have been measured spectrophotometrically for the reactions of paraoxon 1 and parathion 2 with a series of alicyclic secondary amines, OH- and HOO- ions in H2O at 25.0 +/- 0.1 degrees C. A linear Bronsted-type plot with beta(nuc) = 0.40 was obtained for the reactions of 1 with amines and OH-. The reaction has been concluded to proceed through a concerted mechanism. HOO- deviates positively from the linear Bronsted-type plot, implying that the alpha-effect is operative. The magnitude of the alpha-effect (k(HOO-)/k(OH-)) was found to be ca. 55 for the reaction of 1 and 290 for that of parathion 2, indicating that HOO- is highly effective in decomposition of the toxic phosphorus compounds although it is over 4 pKa units less basic than OH-. Among the theories suggested as origins of the alpha-effect (e.g., TS stabilization through an intramolecular H-bonding interaction, solvent effect, and polarizability effect), polarizability effect appears to be the most important factor for the alpha-effect in this study, since the polarizable HOO- exhibits a larger alpha-effect for the reaction of the more polarizable substrate 2.

• 出版日期2013-1-20