tailieunhanh - Pesticide profiles : Toxicity, environmental impact and fate - Chapter 7

Phenoxy và thuốc diệt cỏ axit benzoic Lớp cái nhìn tổng quan và bối cảnh mô tả chung Các thuốc diệt cỏ phenoxy và axit benzoic được đối xử với nhau bởi vì các cấu trúc tương tự và cơ chế của hành động. Thuốc diệt cỏ phenoxy nguyên mẫu là 2,4-D. Đây là hợp chất đầu tiên trong nhóm thuốc diệt cỏ được sản xuất và hiện đang được sử dụng trong hơn 1500 sản phẩm thương mại khác nhau và trong các công thức thuốc diệt cỏ khác nhau (1). Các thuốc diệt cỏ phenoxy tất cả đều dựa. | chapter seven Phenoxy and benzoic acid herbicides Class overview and general description Background The phenoxy and benzoic acid herbicides are treated together because of their similar structures and mechanisms of action. The prototypical phenoxy herbicide is 2 4-D. This was the first compound in this group of herbicides to be produced and is currently used in more than 1500 different commercial products and in many different herbicide formulations 1 . The phenoxy herbicides are all based on the ring-like structure shown in Figure . The phenoxy herbicides have at least one atom of chlorine attached to the ring at various positions. The benzoic acids have a similar structure though they also have an additional CO2H group attached to the ring as shown in Figure . The respective compounds in these two categories are listed in Table . A B Figure Generic structures for phenoxy herbicides A and benzoic acid herbicides B . One of the most controversial phenoxy compounds is 2 4 5-T. This compound was used extensively in the formulations of Agent Orange and other defoliants applied throughout this country and in Southeast Asia during the Vietnam War. The manufacture of 2 4 5-T produced small but significant amounts of a by-product dioxin a powerful cancer-causing compound in test animals. All uses of 2 4 5-T have been banned in the . Phenoxy herbicide usage In 1987 the total use of phenoxy herbicides in the . exceeded million pounds 1 . Nearly 60 is attributed to the use of 2 4-D. During the same year phenoxy compounds accounted for slightly less than 5 of the total herbicide use in the . 1 . 2000 CRC Press LLC Table Phenoxy and Benzoic Acid Herbicides Phenoxy Acids D DB 2 4 5-T Aclonifen Clonifen Cloprop Dichlorprop Fenoxaprop Fluazifop Fluazifop-p-butyl Haloxyfop Isoxapyrifop MCPA MCPB Mecoprop MCPP Quizalofop Quizalofop-p-ethyl Benzoic Acids Chloramben DCPA Dicamba Note indicates that a profile for this compound is .