Departamento de Quimica Fisica y Termodinamica Aplicada, Facultad de Ciencias, Campus Universitario Rabanales, edificio Marie Curie, Universidad de Cordoba, E-14014 Cordoba, Spain.
J Agric Food Chem. 2009 Dec 9;57(23):11292-6. doi: 10.1021/jf902845h.
This paper present ultraviolet-visible absorption spectra of imazamethabenz-methyl (IMBM) (mixture of the isomers methyl 6-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-m-toluate, m-imazamethabenz, and methyl 2-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-p-toluate, p-imazamethabenz) and the corresponding carboxylic acid, imazamethabenz-acid (IMBA). The spectral characteristics are determined as functions of the pH. The appreciable absorbance in the visible (or near-ultraviolet) region of the spectra indicates that the natural photolytic degradation is possible. From variations of the maximum absorbances of the bands, the pK values of 3.4 +/- 0.2 and 9.4 +/- 0.2 were obtained for protonation of the imidazol (=N-) nitrogen and dissociation of the NH imidazol nitrogen of IMBM, respectively. For IMBA, the dissociation pK of the carboxylic group is very close to that of the imidazol (=N-) nitrogen, both being close to 3.3. The dissociation pK of the NH imidazol nitrogen for IMBA is 9.6 +/- 0.2. The role of the acid-base reactions on the sorption on soils of these herbicides is discussed.
本文给出了咪草烟甲酯（IMBM）（异构体混合物，包括甲酯 6-[(RS)-4-异丙基-4-甲基-5-氧代-2-咪唑啉-2-基]-m-甲苯酸酯，m-咪草烟甲酯，和甲酯 2-[(RS)-4-异丙基-4-甲基-5-氧代-2-咪唑啉-2-基]-p-甲苯酸酯，p-咪草烟甲酯）及其相应羧酸，咪草烟酸（IMBA）的紫外-可见吸收光谱。光谱特征随 pH 值而变化。光谱在可见光（或近紫外）区域有明显的吸收，表明可能存在自然光解降解。从最大吸收带的变化，可以得到 IMBM 中咪唑 (=N-)氮质子化和 NH 咪唑氮去质子化的 pK 值分别为 3.4 +/- 0.2 和 9.4 +/- 0.2。对于 IMBA，羧酸基团的离解 pK 值非常接近咪唑 (=N-)氮的离解 pK 值，均接近 3.3。IMBA 的 NH 咪唑氮的离解 pK 值为 9.6 +/- 0.2。本文还讨论了这些除草剂在土壤中吸附的酸碱反应的作用。
