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  • Alkyl 卤化物

    A hand holding a red aerosol spray can, releasing a mist.

    Is the hole in the ozone getting bigger?
    ::臭氧洞是不是越来越大了?

    A class of simple alkyl halides called chlorofluorocarbons (CFCs) was once very widely used in aerosol sprays and as refrigerants. One such example is CCl 3 F, or trichlorofluoromethane. Unfortunately, CFCs are harmful to the ozone layer of our upper atmosphere. Ozone is critical in limiting the amount of damaging ultraviolet radiation that reaches the Earth. CFCs react with the ozone and damage it, leaving the earth less protected.
    ::一种被称为氯氟化碳(CFCs)的简单烷基卤化物曾被广泛用于气雾喷雾剂和制冷剂,例如CCl3F或三氯氟甲烷。不幸的是,氯氟化碳对我们上层大气的臭氧层有害。臭氧对于限制接触地球的损害性紫外线辐射量至关重要。氯氟化碳与臭氧发生反应并造成破坏,使地球得不到保护。

    Beginning in the late 1970’s, ozone depletion was recognized as a significant environmental issue. The most dramatic decrease in ozone occurs seasonally over the continent of Antarctica. The size and duration of the ozone hole steadily increased, with the largest hole recorded in 2006. Fortunately, most countries have recognized the danger of CFCs and dramatically curtailed their use in recent years. It is hoped that ozone depletion will slow and that the ozone layer may eventually be restored to its earlier levels.
    ::从1970年代后期开始,臭氧消耗被公认为一个重大的环境问题。 臭氧消耗最显著的减少发生在南极洲大陆的季节性变化。 臭氧空洞的规模和持续时间在稳步增加,2006年记录了最大的空洞。 幸运的是,大多数国家已经认识到氟氯化碳的危险,并大幅削减了近年来的氟氯化碳使用量。 人们希望臭氧消耗将放缓,臭氧层最终可能恢复到更早的水平。

    Alkyl Halides
    ::Alkyl 卤化物

    An alkyl halide is an organic compound in which one or more halogen atoms are substituted for one or more hydrogen atoms in a . The general formulas for organic molecules with functional groups use the letter R to stand for the rest of the molecule outside of the functional group. Because there are four possible halogen atoms (fluorine, chlorine, bromine, or iodine) that can act as the functional group, we use the general formula R−X to represent an alkyl halide. The rules for naming simple alkyl halides are listed below.
    ::卤化烷是一种有机化合物,其中一种或多种卤素原子替代一种或多种氢原子。具有功能组的有机分子的一般公式使用字母R表示功能组以外的分子。由于可能有四种卤化氢原子(氟、氯、溴或碘)可以作为功能组,我们使用一般公式R-X代表烷基卤化物。下面列出了命名简单烷基卤化物的规则。

    1. Name the parent compound by finding the longest continuous carbon chain that also contains the halogen. Add a prefix for the particular halogen atom. The prefixes for each of the four are fluoro- , chloro- , bromo- , and iodo- . If more than one kind of halogen atom is present, put them in alphabetical order. If there is more than one of the same halogen on a given carbon atom, use the prefixes di- , tri- , or tetra- before the prefix for the halogen.
      ::通过找到含有卤素的最长连续碳链, 命名母体化合物。 为特定的卤素原子添加一个前缀。 四种物质的前缀均为氟、 氯、溴和碘。 如果存在一种以上的卤素原子, 请按字母顺序排列。 如果给定碳原子上含有一个以上的同一种卤素, 请在卤素的前缀之前使用二、 三或四的前缀。
    2. As with hydrocarbons, number the carbon chain in a way that makes the sum of halogen numbers as low as possible. If different halogens are in equivalent positions, give the lower number to the one that comes first in alphabetical order.
      ::与碳氢化合物一样,碳链的编号方式尽可能降低卤素数量的总和。 如果不同的卤素处于等同位置,则给以字母顺序排在首位的碳链以较低的数字。
    3. Add the numerical prefix into the name before the halogen prefix.
      ::将数字前缀添加到卤素前缀之前的名称中。
    4. Separate numbers with commas and separate numbers from names or prefixes with a hyphen. There are no spaces in the name.
      ::带有逗号的单独数字和带有连字符的名称或前缀的单独数字。名称中没有空格。

    Listed below are some examples of names and structural formulas of a few alkyl halides.
    ::下面列举一些例子,说明几片卤化物的名称和结构公式。

    Structural formulas of alkyl halides illustrating naming conventions.

    Note that for the structure based on methane, no number needs to be used since there is only one carbon atom. In the third example, the chloro is listed first alphabetically and the chain is numbered so that the sum of the numbers is as low as possible.
    ::请注意,对于基于甲烷的结构,不需要使用数字,因为只有一个碳原子。 在第三个例子中,氟氯化碳首先按字母顺序排列,链条编号,以便数字的总和尽可能低。

     

     

    Uses of Alkyl Halides
    ::林丹用途

    Alkyl halides are often used as synthetic intermediates in the laboratory. Although these compounds were once widely used as dry cleaning solvents, coolants in refrigerators and air conditioners, and propellants in hairsprays and deodorants, increasing awareness of their toxicity has led to a wide-spread decrease in applications for these materials. Some specific compounds are still used. Halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) is still used in some situations as an inhalation anesthetic. The compound DDT is a very effective pesticide, but is only used when nothing else works because of its harmful effects on .
    ::尽管这些化合物曾被广泛用作干洗溶剂、冰箱和空调中的冷却剂以及发泡管和除臭剂中的推进剂,但人们日益认识到其毒性,导致对这些材料的应用广泛减少,某些特定化合物仍在使用,哈龙(2-溴-2-氯-1,1,1-三氟乙烷)在某些情况下仍被用作吸入麻醉剂,该化合物是一种非常有效的农药,但只有在其他物质无效的情况下,才使用,因为其对此类物质有害的影响。

    Review
    ::回顾

    1. What is an alkyl halide?
      ::什么是烷基卤化物?
    2. Why are alkyl halides not used much commercially these days?
      ::为什么现在碳基卤化物很少用于商业用途?
    3. How are halogens listed in naming?
      ::卤素如何在命名中列出?