📚 Uses of Halogenoalkanes | 卤代烷的用途
Halogenoalkanes are a family of organic compounds in which one or more hydrogen atoms of an alkane have been replaced by halogen atoms (fluorine, chlorine, bromine or iodine). The polar carbon–halogen bond gives many halogenoalkanes distinctive physical properties, such as low boiling points, non-flammability, high density and excellent chemical stability. These properties underpin a remarkably wide range of practical applications, from refrigeration and fire suppression to pharmaceuticals, polymers and pest control. However, the very stability that makes many halogenoalkanes so useful also leads to serious environmental concerns, particularly ozone depletion and global warming. In this article we explore the principal uses of halogenoalkanes, the chemical principles behind each application, and the ongoing shift towards greener alternatives.
卤代烷是一类有机化合物，其中烷烃分子中的一个或多个氢原子被卤素原子（氟、氯、溴或碘）取代。极性的碳–卤键赋予许多卤代烷独特的物理性质，例如低沸点、不燃性、高密度和出色的化学稳定性。这些性质支撑了极为广泛的实际用途，从制冷和灭火到制药、高分子和害虫防治。然而，正是这种使许多卤代烷如此有用的稳定性也导致了严重的环境问题，特别是臭氧层破坏和全球变暖。本文将探讨卤代烷的主要用途、每种应用背后的化学原理，以及当前向更绿色替代品的转型。
1. Refrigerants and Air Conditioning | 制冷剂与空调
Halogenoalkanes are ideal working fluids in vapour-compression refrigeration systems because they possess low boiling points, high latent heats of vaporisation, and are neither toxic nor flammable. Their volatility allows them to absorb heat from the refrigerated space as they evaporate and to release that heat to the surroundings when they are compressed and condensed.
卤代烷是蒸汽压缩制冷系统中理想的工作流体，因为它们具有低沸点、高汽化潜热，且既无毒又不燃。其挥发性使它们能够在蒸发时从冷藏空间吸收热量，并在压缩冷凝时将该热量释放到周围环境中。
The earliest widely used refrigerants were chlorofluorocarbons (CFCs), such as trichlorofluoromethane (CCl₃F, CFC-11) and dichlorodifluoromethane (CCl₂F₂, CFC-12). Their chemical inertness, non-toxicity and excellent thermodynamic properties made them dominant in domestic refrigerators, air conditioners and industrial cooling from the 1930s onwards.
最早广泛使用的制冷剂是氯氟烃（CFCs），例如三氯一氟甲烷（CCl₃F, CFC-11）和二氯二氟甲烷（CCl₂F₂, CFC-12）。它们的化学惰性、无毒性和优异的热力学性质使其从20世纪30年代起在家用冰箱、空调和工业冷却中占据主导地位。
After the link between CFCs and stratospheric ozone depletion was established, these compounds were gradually phased out under the Montreal Protocol. They were replaced first by hydrochlorofluorocarbons (HCFCs) such as chlorodifluoromethane (CHClF₂, HCFC-22), which contain at least one C–H bond and are more readily degraded in the troposphere, and later by hydrofluorocarbons (HFCs) like 1,1,1,2-tetrafluoroethane (CF₃CH₂F, HFC-134a), which contain no chlorine and therefore possess zero ozone-depletion potential.
在确定CFCs与平流层臭氧破坏之间的联系后，这些化合物根据《蒙特利尔议定书》逐步淘汰。它们首先被含氢氯氟烃（HCFCs）所替代，例如一氯二氟甲烷（CHClF₂, HCFC-22），这类分子至少含有一个C–H键，在对流层中更易降解；随后又被氢氟烃（HFCs）替代，如1,1,1,2-四氟乙烷（CF₃CH₂F, HFC-134a），它们不含氯，因此臭氧消耗潜能为零。
The table below summarises key halogenoalkanes used as refrigerants and their characteristics.
| Halogenoalkane | English use / property | 中文用途/性质 |
|---|---|---|
| CCl₃F (CFC-11) | Refrigerant, foam blowing agent; high ODP | 制冷剂、发泡剂；高臭氧消耗潜值 |
| CCl₂F₂ (CFC-12) | Refrigerant in car air conditioning; high ODP | 汽车空调制冷剂；高ODP |
| CHClF₂ (HCFC-22) | Transitional refrigerant; lower ODP | 过渡期制冷剂；较低ODP |
| CF₃CH₂F (HFC-134a) | Zero ODP refrigerant; high GWP | 零ODP制冷剂；高全球变暖潜值 |
2. Solvents, Degreasers and Dry Cleaning | 溶剂、脱脂剂与干洗
Volatile halogenoalkanes are excellent solvents for non-polar and weakly polar organic substances. They dissolve oils, greases, waxes and many organic polymers that are insoluble in water. This makes them valuable in industrial degreasing, dry cleaning and the formulation of adhesives, paints and inks.
挥发性卤代烷是极好的非极性和弱极性有机物的溶剂。它们能溶解油类、油脂、蜡以及许多不溶于水的有机聚合物。这使得它们在工业脱脂、干洗以及粘合剂、涂料和油墨的配方中具有重要价值。
ty advantage over hydrocarbon solvents such as hexane. Dry cleaning fluids often relied on tetrachloroethene (Cl₂C=CCl₂), also known as perchloroethylene, which effectively removes stains from delicate fabrics without causing shrinkage or colour bleeding.
早期工业溶剂包括四氯化碳（CCl₄）和三氯乙烯（CCl₂=CHCl）。它们的不燃性是相对于己烷等碳氢溶剂的重要安全优势。干洗液往往依赖于四氯乙烯（Cl₂C=CCl₂），也称为全氯乙烯，它能有效去除精细织物上的污渍，且不会导致缩水或褪色。
The high density and low boiling point of many halogenated solvents allow them to be recovered by distillation and reused, which improves the economics of the process. However, their toxicity and persistence in groundwater have led to strict regulation, especially for chlorinated solvents, and to the development of aqueous and bio-based degreasing systems.
许多卤代溶剂的高密度和低沸点使其能够通过蒸馏回收并重复使用，从而提高了工艺的经济性。然而，它们的毒性和在地下水中的持久性导致了严格的监管，尤其是对含氯溶剂，并促进了水基和生物基脱脂系统的开发。
3. Fire Extinguishants | 灭火剂
Certain halogenoalkanes, especially those containing bromine, have been used as highly effective fire-suppression agents. They work by interrupting the free-radical chain reactions that sustain combustion. The carbon–bromine bond is relatively weak and breaks readily in a flame, releasing bromine atoms that scavenge hydrogen radicals (H·) and hydroxyl radicals (·OH).
某些卤代烷，特别是含溴的卤代烷，已被用作高效的灭火剂。它们通过中断维持燃烧的自由基链式反应而起作用。碳–溴键相对较弱，在火焰中容易断裂，释放出溴原子，这些溴原子能清除氢自由基（H·）和羟基自由基（·OH）。
The most widely used halogenated fire extinguishants were the halons, such as bromotrifluoromethane (CBrF₃, Halon 1301) and bromochlorodifluoromethane (CBrClF₂, Halon 1211). Halon 1301 was particularly valued for protecting computer rooms, aircraft and museums, because it is electrically non-conductive, leaves no solid residue, and extinguishes fires at concentrations as low as 5–7 % by volume.
最广泛使用的卤代灭火剂是哈龙，例如三氟一溴甲烷（CBrF₃，哈龙1301）和一氯一溴二氟甲烷（CBrClF₂，哈龙1211）。哈龙1301因其不导电、不留固体残留物，且在低至5%–7%的体积浓度下即可灭火，而特别受重视用于保护计算机房、飞机和博物馆。
However, bromine atoms are far more efficient at destroying stratospheric ozone than chlorine atoms. Consequently, the production and use of halons have been severely restricted under the Montreal Protocol, with essential-use exemptions only for aircraft and military applications.
然而，溴原子对平流层臭氧的破坏效率远高于氯原子。因此，哈龙的生产和使用在《蒙特利尔议定书》下受到严格限制，仅对航空和军事用途保留了必要用途豁免。
4. Precursors to Polymers | 聚合物前体
Halogenoalkanes serve as monomers or as intermediates in the manufacture of several hugely important polymers. The carbon–halogen bond in a halogenoalkene can undergo addition polymerisation, yielding high-molecular-mass materials with exceptional thermal and chemical resistance.
卤代烷可作为单体或中间体用于制造几种极为重要的聚合物。卤代烯烃中的碳–卤键可发生加成聚合，生成具有出色耐热性和耐化学性的高分子材料。
erises to form poly(tetrafluoroethene) (PTFE), commonly known as Teflon. PTFE is notable for its extremely low coefficient of friction, non-stick properties and stability up to about 260 °C. It is used to coat non-stick cookware, in laboratory equipment, and as a corrosion-resistant lining for pipes and containers.
四氟乙烯（CF₂=CF₂）聚合生成聚四氟乙烯（PTFE），通常称为特氟龙。PTFE以其极低的摩擦系数、不粘特性和高达约260°C的稳定性而著称。它用于涂覆不粘炊具、实验室设备，以及作为管道和容器的耐腐蚀衬里。
lymerisation of chloroethene (CH₂=CHCl, also known as vinyl chloride), is one of the world' d with plasticisers, is found in flooring, electrical cable insulation and medical tubing.
聚氯乙烯（PVC）由氯乙烯（CH₂=CHCl，亦称乙烯基氯）聚合而成，是世界上生产最广泛的合成塑料之一。硬质PVC用于窗框和管道，而添加了增塑剂的软质PVC则用于地板、电缆绝缘层和医用导管。
5. Anaesthetics | 麻醉剂
Certain halogenated ethers and halogenoalkanes are used as modern inhalation anaesthetics because they produce rapid, smooth induction and recovery, and are non-flammable. Their potency is related to their lipid solubility, which allows them to partition into the lipid membranes of nerve cells and modulate ion channels.
某些卤代醚和卤代烷被用作现代吸入麻醉剂，因为它们能产生快速平稳的诱导和恢复，并且不燃。它们的药效与其脂溶性有关，这使得它们能够分配到神经细胞的脂质膜中并调节离子通道。
Early halogenated anaesthetics included halothane (CF₃CHBrCl), which provided a major advance over flammable ether and cyclopropane. Today, isoflurane (CF₃CHCl–O–CHF₂), sevoflurane (CHF₂OCH₂CF₃) and desflurane (CF₃CHFOCHF₂) are among the most commonly used agents. They are designed to be chemically stable during storage and minimally metabolised in the body, reducing the burden on the liver.
早期的卤化麻醉剂包括氟烷（CF₃CHBrCl），它相对于易燃的乙醚和环丙烷来说是一项重大进步。如今，异氟烷（CF₃CHCl–O–CHF₂）、七氟烷（CHF₂OCH₂CF₃）和地氟烷（CF₃CHFOCHF₂）是最常用的药剂。它们在设计上力求在储存期间保持化学稳定，并在体内被最低限度代谢，从而减轻肝脏负担。
6. Pesticides and Insecticides | 农药与杀虫剂
Many organochlorine compounds have historically been used as potent contact insecticides because they are neurotoxic to insects and have long-lasting residual activity in soil and on crops. The low reactivity of the C–Cl bond contributes to their persistence in the environment.
历史上，许多有机氯化合物被用作强力触杀性杀虫剂，因为它们对昆虫具有神经毒性，并在土壤和作物上具有持久残留活性。C–Cl键的低反应性导致了它们在环境中的持久性。
The best known example is DDT (dichlorodiphenyltrichloroethane, C₁₄H₉Cl₅), which was hugely effective in controlling malaria-transmitting mosquitoes and in agricultural pest management. Other organochlorine insecticides include lindane (γ-hexachlorocyclohexane) and aldrin. However, their bioaccumulation, persistence in fatty tissues, and toxicity to non-target species, particularly birds and aquatic life, led to bans or severe restrictions in many countries.
最著名的例子是DDT（双对氯苯基三氯乙烷，C₁₄H₉Cl₅），它在控制传播疟疾的蚊子和农业害虫管理方面非常有效。其他有机氯杀虫剂包括林丹（γ-六氯环己烷）和艾氏剂。然而，它们在脂肪组织中的生物积累、持久性以及对非目标物种（特别是鸟类和水生生物）的毒性，导致许多国家对其禁用或严格限制。
7. Flame Retardants | 阻燃剂
Brominated halogenoalkanes and brominated aromatic compounds are used as additive or reactive flame retardants in plastics, textiles, electronics and furniture foams. Their mechanism is similar to that of halon fire extinguishants: at high temperatures they release bromine radicals that inhibit the flame's radical chain chemistry.
溴化卤代烷和溴化芳香族化合物被用作塑料、纺织品、电子产品和家具泡沫中的添加型或反应型阻燃剂。其机理与哈龙灭火剂相似：在高温下它们释放出溴自由基，抑制火焰的自由基链式化学反应。
Common examples include polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol A (TBBPA). These substances significantly reduce the ignitability and fire spread of materials. However, concerns about their persistence, bioaccumulation and potential endocrine-disrupting effects have prompted the phase-out of certain PBDEs and a search for phosphorus- or nitrogen-based alternatives.
常见例子包括多溴联苯醚（PBDEs）和四溴双酚A（TBBPA）。这些物质显著降低了材料的可燃性和火势蔓延速度。然而，对其持久性、生物累积性和潜在内分泌干扰效应的担忧，已促使某些PBDEs逐步淘汰，并促使人们寻找基于磷或氮的替代品。
8. Pharmaceuticals and Intermediates | 医药与中间体
Halogenoalkanes are essential building blocks in pharmaceutical synthesis. The presence of a halogen atom can dramatically alter a molecule's metabolic stability, lipophilicity and binding affinity to biological targets. As a result, around 20–25 % of marketed drugs contain at least one halogen substituent.
卤代烷是药物合成中必不可少的结构单元。卤素原子的存在可以显著改变分子的代谢稳定性、亲脂性以及与生物靶标的结合亲和力。因此，约20%–25%的上市药物至少含有一个卤素取代基。
For example, the anti-cancer drug bendamustine contains a chloroethylamine group that alkylates DNA; the antibiotic vancomycin carries chlorine atoms that influence its antibiotic activity; and many fluorinated intermediates (such as 2,2,2-trifluoroethylamine) are used to construct drug molecules with enhanced bioavailability. Halogenoalkanes also serve as alkylating agents to introduce functional groups into complex organic frameworks.
例如，抗癌药苯达莫司汀含有一个能烷基化DNA的氯乙胺基团；抗生素万古霉素携带的氯原子影响其抗菌活性；许多含氟中间体（如2,2,2-三氟乙胺）被用来构建具有增强生物利用度的药物分子。卤代烷还作为烷基化试剂，将官能团引入复杂的有机骨架中。
9. Environmental Impact of Halogenoalkanes | 卤代烷的环境影响
The widespread use of halogenoalkanes has come at a significant environmental cost. The most famous issue is stratospheric ozone depletion. When CFCs and halons rise into the stratosphere, UV radiation breaks the relatively weak C–Cl or C–Br bond, generating chlorine or bromine atoms that catalyse the destruction of ozone molecules. A single chlorine atom can destroy over 100,000 ozone molecules before being removed from the stratosphere.
卤代烷的广泛使用带来了显著的环境代价。最著名的问题是平流层臭氧破坏。当CFCs和哈龙上升到平流层时，紫外线辐射使相对较弱的C–Cl或C–Br键断裂，产生氯原子或溴原子，这些原子催化破坏臭氧分子。单个氯原子在离开平流层之前就可破坏超过100,000个臭氧分子。
This process is described by the simplified catalytic cycles:
Cl· + O₃ → ClO· + O₂
ClO· + O → Cl· + O₂
该过程可用简化的催化循环描述：
Cl· + O₃ → ClO· + O₂
ClO· + O → Cl· + O₂
d by Cl or Br. This damage led to the Antarctic ozone hole and prompted international action.
净结果是O₃ + O → 2O₂，由Cl或Br催化。这种破坏导致了南极臭氧空洞，并促成了国际行动。
Additionally, many halogenoalkanes are potent greenhouse gases. The GWP of HFC-134a, for instance, is 1430 times that of CO₂ over a 100-year horizon. Therefore, their emission contributes to global warming even when ozone depletion is not a concern.
此外，许多卤代烷是强效温室气体。例如，HFC-134a的100年全球变暖潜值是CO₂的1430倍。因此，即使不涉及臭氧消耗，它们的排放也会加剧全球变暖。
10. Green Chemistry and Alternatives | 绿色化学与替代品
mpact. Hydrofluoroolefins (HFOs), such as 2,3,3,3-tetrafluoropropene (CF₃CF=CH₂, HFO-1234yf), contain a carbon– egrade within days to weeks, giving them an ODP of zero and a very low GWP of less than 1.
为响应环境法规，化学工业已开发出环境影响降低的新一代卤代烷。氢氟烯烃（HFOs），如2,3,3,3-四氟丙烯（CF₃CF=CH₂，HFO-1234yf），含有一个碳–碳双键，使其在对流层中反应活性大大提高。它们在几天到几周内降解，因此臭氧消耗潜能为零，全球变暖潜值极低（小于1）。
Beyond fluorinated molecules, there is a growing push towards not-in-kind alternatives: carbon dioxide as a refrigerant (R-744), water-based degreasing, phosphate-based flame retardants, and biological pest control methods. Nonetheless, halogenoalkanes remain indispensable in many specialised fields, and their sustainable use depends on containment, recycling and destruction of existing stockpiles.
除了含氟分子之外，人们日益推动非同类替代品：二氧化碳作为制冷剂（R-744）、水基脱脂、磷酸酯基阻燃剂以及生物害虫防治方法。尽管如此，卤代烷在许多专业领域中仍然不可或缺，其可持续使用依赖于密封、回收以及销毁现有库存。
11. Summary | 总结
The uses of halogenoalkanes illustrate a classic tension between technological utility and environmental responsibility. Their unique combination of volatility, stability and non-flammability has made them central to modern life in refrigeration, fire safety, medicine and materials. Yet the very stability that confers these benefits also leads to long atmospheric lifetimes, ozone destruction and significant global warming potential. Understanding the applied chemistry of halogenoalkanes allows us not only to appreciate their versatility but also to make informed choices about replacement strategies and sustainable chemical design.
卤代烷的用途体现了技术效用与环境责任之间的经典矛盾。它们独特的挥发性、稳定性和不燃性组合使其成为现代生活中制冷、消防安全、医药和材料领域的核心。然而，正是带来这些益处的稳定性导致了长大气寿命、臭氧破坏以及显著的全球变暖潜值。理解卤代烷的应用化学，不仅使我们领略其多功能性，也有助于我们在替代策略和可持续化学设计方面做出明智的选择。
Published by TutorHao | Chemistry Revision Series | aleveler.com
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