关于基有机化合物的前景
Prasada Rao S Kodavanti1, Lucio G Costa2,3, Michael Aschner4
1Neurological and Endocrine Toxicology Branch, PHITD/CPHEA/ORD, US Environmental Protection Agency, Research Triangle Park, NC, United States.
概括
化有机化学品 (HOCs) 污染环境,并对健康构成风险,包括癌症和糖尿病. 由于其持久性和广泛使用,了解和预防高合物暴露至关重要.
科学领域:
- 环境科学 环境科学
- 毒理学 毒理学 毒理学
- 公共卫生 公共卫生
背景情况:
- 化有机化学品 (HOCs) 在各种行业中广泛使用,导致全球环境污染.
- 这些持久化学物质在环境介质和人体组织中积累,引发生态和健康问题.
研究的目的:
- 审查HOCs对环境的广泛污染情况.
- 为了突出与高合物暴露相关的不良健康影响.
- 讨论HOC使用的趋势和持续警的需要.
主要方法:
- 对HOC研究的文献综述.
- 对环境和人体组织监测数据的分析.
- 审查有关HOCs的监管行动和行业趋势.
主要成果:
- 在全球范围内,HOCs存在于空气,水,土壤和人体组织中.
- 暴露于HOCs与生殖,神经,内分泌和致癌作用,以及肥胖和2型糖尿病有关.
- 虽然一些较旧的HOC已经下降,但像PBDE和PFAS这样的新产品正在增加.
结论:
- 人类暴露于HOCs可能会继续,因为它们的持久性和广泛使用.
- 预防措施和全面了解高氧化碳对健康的影响至关重要.
- 监管行动已经影响了HOC的使用,但需要持续监测和研究.
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相关概念视频
Reactions at the Benzylic Position: Halogenation
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Benzylic halogenation takes place under conditions that favor radical reactions such as heat, light, or a free radical initiator like peroxide.
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Halogenation of Alkenes
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Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
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ortho–para-Directing Deactivators: Halogens
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Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...
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Alkyl Halides
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Structural Properties
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
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Radical Halogenation: Stereochemistry
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Stereochemistry is the study of the different spatial arrangements of atoms in a given molecule. The stereochemistry of radical halogenations can be understood from three different situations:
Halogenation to form a new chiral center:
Halogenation to form a new chiral center:
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Radical Halogenation: Thermodynamics
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The thermodynamic favorability of a reaction is determined by the change in Gibbs free energy (ΔG). ΔG has two components- enthalpy (ΔH) and entropy (ΔS). The entropy component is negligible for alkane halogenation because the number of reactants and product molecules are equal. In this case, the ΔG is governed only by the enthalpy component. The most crucial factor that determines ΔH is the strength of the bonds. ΔH can be determined by comparing the energy...
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