51-90-1Relevant articles and documents
Enhanced mineralization of diuron using a cyclodextrin-based bioremediation technology
Villaverde, Jaime,Posada-Baquero, Rosa,Rubio-Bellido, Marina,Laiz, Leonila,Saiz-Jimenez, Cesareo,Sanchez-Trujillo, Maria A.,Morillo, Esmeralda
, p. 9941 - 9947,7 (2020/09/15)
The phenylurea herbicide diuron [N-(3,4-dichlorophenyl)-N,N-dimethylurea] is widely used in a broad range of herbicide formulations and, consequently, it is frequently detected as a major soil and water contaminant in areas where there is extensive use. Diuron has the unfortunate combination of being strongly adsorbed by soil organic matter particles and, hence, slowly degraded in the environment due to its reduced bioavailability. N-Phenylurea herbicides seem to be biodegraded in soil, but it must be kept in mind that this biotic or abiotic degradation could lead to accumulation of very toxic derived compounds, such as 3,4-dichloroaniline. Research was conducted to find procedures that might result in an increase in the bioavailability of diuron in contaminated soils, through solubility enhancement. For this purpose a double system composed of hydroxypropyl-β-cyclodextrin (HPBCD), which is capable of forming inclusion complexes in solution, and a two-member bacterial consortium formed by the diuron-degrading Arthrobacter sulfonivorans (Arthrobacter sp. N2) and the linuron-degrading Variovorax soli (Variovorax sp. SRS16) was used. This consortium can achieve a complete biodegradation of diuron to CO2 with regard to that observed in the absence of the CD solution, where only a 45% biodegradation was observed. The cyclodextrin-based bioremediation technology here described shows for the first time an almost complete mineralization of diuron in a soil system, in contrast to previous incomplete mineralization based on single or consortium bacterial degradation.
Nucleophilic 1,2-Schifts of Alkoxycarbonyl and Carboxylate Groups in the Benzilic-Acid Type Rearrangement of α,β-Dioxobutiric Esters
Gowal, Heike,Dao, Le H.,Dahn, Hans
, p. 173 - 180 (2007/10/02)
tert-Butyl α,β-dioxobutyrate (hydrate; 1d) undergoes, at medium or high pH, the benzylic acid rearrangement with exclusive 1,2-shift of the COO(t-Bu) group; the same is the true for the corresponding isopropyl ester 1c and ethyl ester 1b at high pH, whereas the overall picture of these reactions is complicated by concurrent hydrolysis of the ester, followed by a 1,2-shift of the COO1- group.Consequently, the shift of these electron-attracting groups cannot be considered to be systematically disfavoured (compared, e.g., with alkyl-group shifts).Kinetic measurements of the rearrangement show for both esters (as well as for the analogous ethyl ester 1b, and also for ethyl 3-cyclopropyl-α,β-dioxopropionate (4)) a characteristic rate profile: at relatively low pH, k is proportional to 1->, approaching saturation with increasing 1-> (interpreted as complete transformation of the substrate into the hydrate monoanion), which is followed at higher pH by another rate increase with k proportional to 1-> (probably due to the reaction of the hydrate dianion).The similarity of k values for 1b-d shows that in the shift of COOR steric hindrance caused by R is negligible.
