Organic Chemistry 翻译

Organic Chemistry

The nature of Organic Chemistry has changed greatly since 1828. Before that time the scientific philosophy known as “Vitalism” maintained that Organic Chemistry was the chemistry of living systems. It maintained that organic compounds could only be produced within living matter while inorganic compounds were synthesized from non-living matter. Even the word “organic” comes from the same root as the word “organism” or “organ”. However people like Professor Wohler beginning in 1828 determined that it was indeed possible to synthesize organic compounds from those compounds that were considered inorganic. One of the first organic compounds synthesized from basically inorganic compounds was the compound Urea which is a metabolic product of urine. It was synthesized from Ammonium Cyanate considered a compound produced outside of living matter and therefore considered inorganic. Since then many millions of Organic compounds have been synthesized “in vitro” in other words outside living tissue.

1 Structural formulas

The building block of structural organic chemistry is the tetravalent carbon atom. With few exceptions, carbon compounds can be formulated with four covalent bonds to each carbon, regardless of whether the combination is with carbon or some other element. The two-electron

bond, which is illustrated by the carbon-hydrogen bonds in methane or ethane and the carbon-carbon bond in ethane, is called a single bond. In these and many related substances, each carbon is attached to four other

atoms:

There exist, however, compounds such as ethene (ethylene), C2H4, in which two electrons from each of the carbon atoms are mutually shared, thereby producing two two-electron bonds, an arrangement which is called a double bond. Each carbon in ethene is attached to only three

other atoms:

Similarly, in ethyne (acetylene), C2H2, three electrons from each carbon atom are mutually shared, producing three two-electron bonds, called a

triple bond, in which each carbon is attached to only two other atoms:

By convention, a single straight line connecting the atomic symbols is used to represent a single (two-electron) bond, two such lines to represent a double (four-electron) bond, and three lines a triple (six-electron) bond. Representations of compounds by these symbols are called structural formulas; some examples are

To save space and time in the representation of organic structures, it is common practice to use “condensed formulas” in which the bonds are not shown explicitly. In using condensed formulas, normal atomic valences

are understood throughout. Examples of condensed formulas are

Another type of abbreviation that often is used, particularly for ring compounds, dispenses with the symbols for carbon and hydrogen atoms and leaves only the lines in a structural formula. For instance, cyclopentane, C5H10, often is represented as a regular pentagon in which it is understood that each apex represents a carbon atom with the requisite

number of hydrogens to satisfy the tetravalence of carbon:

2 Organic nomenclature

Organic nomenclature is the system established for naming and grouping organic compounds.

Formally, rules established by the International Union of Pure and

Applied Chemistry (known as IUPAC nomenclature) are authoritative for the names of organic compounds, but in practice, a number of simply-applied rules can allow one to use and understand the names of many organic compounds.

For many compounds, naming can begin by determining the name of the parent hydrocarbon and by identifying any functional groups in the molecule that distinguish it from the parent hydrocarbon. The numbering of the parent alkane is used, as modified, if necessary, by application of the Cahn-Ingold-Prelog priority(CIP priority) rules in the case that ambiguity remains after consideration of the structure of the parent hydrocarbon alone. The name of the parent hydrocarbon is modified by the application of the highest-priority functional group suffix, with the remaining functional groups indicated by numbered prefixes, appearing in the name in alphabetical order from first to last.

In many cases, lack of rigor in applying all such nomenclature rules still yields a name that is intelligible-the aim, of course, being to avoid any ambiguity in terms of what substance is being discussed.

For instance, strict application of CIP priority to the naming of the compound-NH2CH2CH2OH

2-aminoethanol,which is would preferred. render the name the as name However,

2-hydroxyethanamine unambiguously refers to the same compound. How the name was constructed:

(1)There are two carbons in the main chain; this gives the root name “eth”.

(2)Since the carbons are singly-bonded, the suffix begins with “an”.

(3)The two functional groups are an alcohol (OH) and an amine (NH2). The alcohol has the higher atomic number, and takes priority over the amine. The suffix for an alcohol ends in “ol”, so that the suffix is “anol”.

(4)The amine group is not on the carbon with the OH (the #1 carbon), but one carbon over (the #2 carbon); therefore we indicate its presence with the prefix “2-amino”.

(5)Putting together the prefix, the root and the suffix, we get “2-aminoethanol”.

There is also an older naming system for organic compounds known as common nomenclature , which is often used for simple, well-known compounds, and also for complex compounds whose IUPAC names are too complex for everyday use.

Simplified molecular input line entry specification (SMILES) strings are commonly used to describe organic compounds, and as such are a form of“naming” them.

3 Functional groups

Functional groups are groups of atoms that confer similar properties onto otherwise dissimilar molecules. Carbon, nitrogen, oxygen, hydrogen, and phosphorus are a few of the elements involved in forming functional

groups. Carbon can make four bonds. Nitrogen makes three, oxygen two, and hydrogen one.

译文：

第二课 有机化学

自从1828年以来，有机化学的性质发生了很大变化。此前的科学理念“活力论”认为，有机化学是化学上的生命系统。它坚持认为有机化合物只能在生命物质的产生，而无机化合物却要从非生命物质的合成而来。而“有机”一词也和单词“有机体”或“有机物”同根。然而许多人比如沃勒教授在1828年年初确定它确实是有可能从那些被认为是无机化合物的有机化合物中合成的。第一个从基本无机化合物合成的化合物是有机复合尿素，它是一种代谢产物的尿液。这是从合成氰酸铵化合物的外部产生的，被认为是生命物质，因此被认为无机物。从

那时起其他活的组织“体外”就有上百万的有机化合物被合成。

1 结构式

有机化学结构组成部分是四价碳原子。除了少数外，不论是否有碳或其他元素组合，碳化合物的每个碳可以产生四个共价键。下面的两个电子式，是表示甲烷或乙烷和乙烷的碳碳键和碳氢键，称为单键。在这些许多相关的物质中，每个碳原子连接到其他四个氢原子：

甲烷 乙烷

然而存在着其它类型的碳碳键，如乙烯化合物（乙烯），C2H4，其中氢有两个电子与每个碳原子共用，从而产生两两电子对，被称为一个双键。乙烯中碳与碳相互连接的电子只有三个：

乙烯

同样，在乙炔（乙炔），C2H4，三个来自每个碳原子的电子相互共用，产生三个双电子对，称为三键，其中每个碳附加其他原子只有两个电子：

乙炔

按照惯例，一条单一的直线连接的原子符号是用来表示单（双电子）键，两条这样的线来表示一个双（四电子）键，三条线表示一各三（六电子）键。这些符号所表述的化合物称为结构式，如下面的例子：

乙烷 乙烯 乙炔

在有机结构中为了节省空间和时间，通常是使用“简写式“，但其中的电 子对未显示明确。在使用简写式时，需要理解正常原子的价态。简写式的例子：

乙烷 乙烯 乙炔

另一种经常使用的简写式，特别是环状化合物。碳和氢原子的主链和支链只存在一个结构式类型。例如，环戊烷，C5H10，往往表现为一个正五边形，其中每个顶点都表示了一个必要的氢原子，以满足碳原子的碳四价：

环戊烷

2 有机命名

系统命名法是对有机化合物的分组和命名方法。在形式上，由国际纯粹与应用化学联合会（IUPAC）制定的规则是有机化合物的命名的权威，但在实践中，简单地运用这个规则可以允许一个人使用和理解很多有机化合物的名字。

对于许多有机化合物，开始可以通过确定碳碳主链和官能团以确定支链从而进行命名。烷烃主链使用编号，修改后，如有必要，可通过卡恩，英戈尔德- Prelog优先级（CIP优先级）涉及的歧义后，烃结构主链仍考虑适用单独规则。主链烃名称修改的最高优先级由后缀官能团决定，其余的官能团别表示编号的前缀，从第一次出现在名称的字母顺序的最后。

在许多情况下，在运用所有这些命名规则仍然缺乏一个严谨的名称，是可以理解的，这样做的目的，当然是避免任何物质正在讨论的条款含糊不清。例如，严格的CIP优先适用于复合基团，如把NH2CH2CH2OH命名为2-氨基乙醇，这是首选的名称。但是，名称2 –hydroxyethanamine也明确指的是同一化合物。 如何命名：

（1）有两个主链碳原子，给这个化合物的根的名称是“eth“。

（2）由于是碳碳单键，后缀为“一“。

（3）两个官能团是醇基（—OH）和氨基（—NH2）。醇基具有较高的分子量，

优先于氨基。对于醇基后缀结尾的“醇“，这样的后缀是“醇“。

（4）氨基团是不是与—OH连接（排名第一的碳）的碳，而是另一个碳（排名第二的碳），因此我们指明其前缀“2 -氨基“的存在。

（5）把前缀和后缀的根放在一起，就得到“2-氨基乙醇“。

此外，还有一个作为共同的术语，这是经常用于简单的，众所周知的化合物，以及为谁的IUPAC命名法是日常使用太复杂的化合物也被称为大分子有机化合物的命名系统。

简化分子输入行输入规范（SMILES）通常用于描述有机化合物，因此也是一种“命名“它们的形式。

3 官能团

原子组成的官能团，可以决定不同的分子的属性。碳，氮，氧，氢，磷是一种涉及容很少而形成的官能团。碳可以提供四个价键，使之形成三氮，氧二，氢一。

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