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专业英语教案03羧酸衍生物

Lesson 3 Derivatives of Carboxylic Acids

第三课羧酸的衍生物

Acid halides, acid anhydrides, esters, and amides are all functional derivatives of carboxylic acids.酰基卤化物,酸酐,酯,酰胺都是羧酸官能团的衍生物。 A general formula for the characteristic structural feature of each of these derivatives is:这些衍生物典型结构特征的一般形式是:

RCOX (acid halide), 酰基卤化物,RCOOCOR (acid anhydride), 酸酐RCOOR (ester) 酯and RCONH2 (amide).酰胺

One way to relate the structural formulas of these functional groups to the structural formula of a carboxylic acid is to imagine a reaction in which -OH from the carboxyl and -H from a mineral acid, a carboxylic acid, an alcohol, or an amine is removed as water and the remaining atoms are joined将官能团结构形式与羧酸的结构联系起来的一个方法是想象羧酸的羟基与无机酸、有机酸、醇或者与胺的H反应以水的形式离去,而剩下的部分就以下面的方式连接起来。

CH3COOH + HCl → H3COCl + H2O

(a carboxylic acid) mineral acid) (an acid chloride)

CH3COOH + HO-COCH3 → CH3COOCOCH3 + H2O

(a carboxylic acid) (a carboxylic acid) (an anhydride) (water)

CH3COOH + HO-CH3 → CH3COOCH3 + H2O

(a carboxylic acid) (an alcohol) (an ester) (water)

CH3COOH + H-NH2 → CH3-CO-NH2 + H2O

(a carboxylic acid) (ammonia) (an amide) (water)

Acid Halides酰基卤化物

The characteristic structural feature of an acid halide is the presence of an -CO-X group, where -X is a halogen, F. CI, Br, or I. 酰氯最典型的结构特征是有一个-CO-X基团,-X是卤原子F, CI, Br, 或者I。Acid halides are named as derivatives of carboxylic acids by replacing the suffix -ic acid by -yl, and adding the name of the halide酰氯的名称是通过将羧酸的后缀-ic用-yl取代后加上卤原子的名称衍生而来的。Following are names and structural formulas for two acid halides.下面是两种酰氯的名称和分子式结构:

CH3COCl [ethanoyl chloride(acetyl chloride)]乙酰氯

C6H5COBr (benzoyl bromide)苯甲酰氯

Of the acid halides, acid chlorides are the more commonly prepared and used in both the laboratory and in industrial organic chemistry.在酰基卤化物中,酰氯是有机化学实验室和工业上生产和使用的最普遍的。Acid chlorides are most often prepared by the reaction of a carboxylic acid with either thionyl chloride or phosphorus pentachloride in much the same way that alkyl chlorides are prepared from alcohols.和用醇制备烷基氯的方法一样,酰氯大多数是由一种羧酸和亚硫酰二氯或者是五氯化磷反应得到。

CH3COOH + ClSOCl → CH3COCl + HCl + SO2

acetic acid thionyl chloride acetyl chloride

C6H5COOH + PC l5 → C6H5COCl + POCl3 + HCl

benzoic acid phosphorus benzoyl phosphorus

pentachloride chloride oxychlorid

Of the four functional derivatives of carboxylic acids we will discuss, acid halides are the most reactive.在我们将要讨论的四种羧酸的衍生物中,酰氯是最容易发生反应的。They react readily with water to form carboxylic acids, with alcohols and phenols to form esters, and with ammonia and primary and secondary amines m form amides.他们很容易和水反应生成羧酸,和醇和苯酚反应生成酯,和氨水和一级、二级胺反应生成酰胺。

Acid Anhydrides酸酐

The characteristic structural feature of an acid anhydride is the presence of a -CO-O-CO- group. 酸酐的结构特征是有一个CO-O-CO-基团的存在。Two examples of symmetrical anhydrides——that is, anhydrides derived from a single carboxylic acid——are acetic anhydride and benzoic anhydride.两个对称的酸酐的例子(就是从一种酸酸衍生而来的酸酐)是乙酸酐和苯甲酸酐。

In the IUPAC system, anhydrides are named by adding the word "anhydride" to the name of the parent acid. 在IUPAC系统中,对酸酐的命名方法是在母酸的名字后面加一个酐字。The anhydride derived from two molecules of acetic acid is named acetic anhydride; that derived from two molecules of benzoic acid is named benzoic anhydride.由两个乙酸衍生而来的酸酐叫做乙酸酐,由两个苯甲酸衍生而来的酸酐叫做苯甲酸酐。

Of the four classes of functional derivatives of carboxylic acid discussed in this unit, acid anhydrides are very close in relative reactivity to acid halides.在本单元讨论的四种羧酸的官能团衍生物中,酸酐的反应活性与酰卤相似。Acid anhydrides react with water to form carboxylic acids, with alcohols to form esters, and with ammonia and primary and secondary amines to form amides.酸酐与水反应生成羧酸,与醇反应生成酯,与氨水和一级、二级胺反应生成酰胺。Thus, they too are valuable starting materials for preparing these functional groups.因此,酸酐也是生产这些官能团的很有价值的原料。

The most commonly used acid anhydride is acetic anhydride, and this compound is commercially available. 最常用的酸酐是乙酸酐,也是商业上可以获得的。Other anhydrides can be prepared by reaction of an acid halide with the sodium or potassium salt of a carboxylic acid. 其他的酸酐可以通过酸性卤化物与羧酸的纳盐或者钾盐反应来制备。In this reaction, the carboxylate anion is the nucleophile that reacts with the carbonyl carbon of the acid chloride to form a tetrahedral carbonyl addition intermediate that then collapses to give the acid anhydride. 在这个反应中,羧酸盐阴离子是亲核试剂与酸性卤化物的羰基碳进行反应形成四面体的羰基加成中间产物然后四面体坍塌得到酸酐。An example of this reaction is formation of the mixed anhydride between benzoic acid and acetic acid.这种反应例子是在苯甲酸乙酸间形成混合酸酐。