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TOXICOLOGICAL CHEMISTRY AND BIOCHEMISTRY - CHAPTER 16

Organohalide hợp chất 16,1 hợp chất GIỚI THIỆU Organohalide hydrocarbon halogen-thay thế với một loạt các tính chất vật lý và hóa học được sản xuất với số lượng lớn như dung môi, chất lỏng truyền nhiệt, trung gian hóa học, và cho các ứng dụng khác. Họ có thể được bão hòa (alkyl halogenua), không bão hòa (alkenyl halogenua), hoặc thơm (aryl halogenua). Các phương tiện chủ yếu của tổng hợp các hợp chất organohalide được thể hiện bằng các ví dụ ở chương 13 và bao gồm thay thế halogenation, halogenation . | Chapter 16 Organohalide Compounds 16.1 introduction Organohalide compounds are halogen-substituted hydrocarbons with a wide range of physical and chemical properties produced in large quantities as solvents heat transfer fluids chemical intermediates and for other applications. They may be saturated alkyl halides unsaturated alkenyl halides or aromatic aryl halides . The major means of synthesizing organohalide compounds are shown by examples in Chapter 13 and include substitution halogenation addition halogenation and hydrohalogenation reactions illustrated in reactions 13.2.2 13.2.3 and 13.2.4 respectively. Most organohalide compounds are chlorides chlorocarbons and chlorohydrocarbons but they also include compounds of fluorine bromine and iodine as well as mixed halides such as the chlorofluorocarbons. The chemical reactivities of organohalide compounds vary over a wide range. The alkyl halides are generally low in reactivity but may undergo pyrolysis in flames to liberate noxious products such as HCl gas. Alkenyl halides may be oxidized which in some cases produces highly toxic phosgene as shown by the following example ClC CÍCl O2 - HCl Cl-C-Cl CO H Cl Trichloroethylene Phosgene 16.1.1 The toxicities of organohalide compounds vary widely. For example dichlorodifluoromethane Freon-12 is generally regarded as having a low toxicity except for narcotic effects and the possibility of asphyxiation at high concentration. Vinyl chloride see Section 16.3 however is a known human carcinogen. The polychlorinated biphenyls PCBs are highly resistant to biodegradation and are extremely persistent in the environment. 16.1.1 Biogenic Organohalides Organohalides were once regarded as being produced exclusively by human activities. However more recent investigations have shown that organisms including algae and fungi release a variety of organohalides and more than 2000 compounds from these biogenic sources have now been identified.1 Most of these compounds are organochlorine .