tailieunhanh - Pesticide profiles : Toxicity, environmental impact and fate - Chapter 4

Thio-và dithiocarbamates . Tổng quan về lớp và bối cảnh mô tả chung Thio-và dithiocarbamates từng có một lớp con đặc biệt của carbamate. Như tên lớp học bao hàm sự, thiocarbamates có một nguyên tử lưu huỳnh thay thế cho một nguyên tử oxy; dithiocarbamates, có hai nguyên tử oxy thay thế bằng lưu huỳnh. Các cấu trúc chung của các thiocarbamates và dithiocarbamates được minh họa trong Hình , Bảng liệt kê các thiocarbamate khác nhau và các hợp chất dithiocarbamate. Như là đúng với carbamates, nhóm R có thể tham khảo alkyl, aryl, thế alkoxy, amide, hoặc kim. | chapter four Thio- and dithiocarbamates . Class overview and general description Background Thio- and dithiocarbamates are each a special subclass of carbamates. As the class names imply thiocarbamates have one sulfur atom substituted for an oxygen atom dithiocarbamates have two oxygen atoms replaced by sulfur. The general structures of the thiocarbamates and dithiocarbamates are illustrated in Figure Table lists the various thiocarbamate and dithiocarbamate compounds. As is true with the carbamates the R groups may refer to alkyl aryl alkoxy amide or metallic substituents 1 . The ethylene bis dithiocarbamates EBDCs commonly contain a metal in a complex or in a polymeric form 1 . A B Figure Generic structures for thiocarbamates A and dithiocarbamates B . In the past the EBDCs were the focus of considerable media and public attention because of concern about the long-term effects of exposure to the EBDCs and their breakdown product ethylene thiourea ETU 2 . These issues are discussed in greater detail in the section regarding the toxicological effects. Thiocarbamate and dithiocarbamate use The thio- and dithiocarbamates are widely used mainly as fungicides on crops in the field or to protect against fungal diseases or rot during harvesting transport and storage. Some of them such as EPTC and molinate may be used for other purposes such as the control of non-crop plants. They may be used in several forms including granular formulations and emulsifiable concentrates. Most if not all of the thiocarbamates and dithiocarbamates are registered as General Use Pesticides GUPs 3 4 . Mode of action and toxicology Thiocarbamates will have similar action to the carbamates whose primary effects on target and non-target species are through the inhibition of a enzyme known as 2000 CRC Press LLC Table Thiocarbamates Butylate Cartap Cycloate Diallate Dimepiperate EPTC Esprocarb Fenothiocarb Methasulfocarb Molinate Orbencarb Pebulate Prosulfocarb Pyributicarb .