Introduction to Organic Chemistry | 有机化学入门

📚 Introduction to Organic Chemistry | 有机化学入门

Organic chemistry is the branch of chemistry that studies carbon-containing compounds. These compounds range from simple fuels such as methane to complex biological molecules such as proteins and DNA. At A-Level, a strong introduction builds the language, representations, classification and reactivity patterns needed for every later topic.

有机化学是研究含碳化合物的化学分支。这些化合物从甲烷等简单燃料到蛋白质和 DNA 等复杂生物分子。在 A-Level 阶段，扎实的入门为后续所有主题打下语言、表示方法、分类和反应规律的基础。

1. What Is Organic Chemistry? | 什么是有机化学？

Organic chemistry is the study of carbon-containing compounds, excluding simple inorganic carbon compounds such as carbon dioxide, carbon monoxide, carbonates and hydrogencarbonates.

有机化学是研究含碳化合物的化学分支，但不包括二氧化碳、一氧化碳、碳酸盐和碳酸氢盐等简单无机碳化合物。

Carbon forms strong covalent bonds with other carbon atoms and with elements such as hydrogen, oxygen, nitrogen, sulfur, phosphorus and the halogens. This ability leads to an enormous variety of organic molecules.

碳能与其他碳原子以及与氢、氧、氮、硫、磷和卤素等元素形成牢固的共价键。这种能力导致有机分子的种类极其丰富。

At Cambridge A-Level, organic chemistry is built around functional groups, nomenclature, isomerism and reaction mechanisms. These foundations are applied to alkanes, alkenes, halogenoalkanes, alcohols, aldehydes, ketones, carboxylic acids, esters, amines and nitriles.

在剑桥 A-Level 阶段，有机化学围绕官能团、命名、异构现象和反应机理展开。这些基础应用于烷烃、烯烃、卤代烷、醇、醛、酮、羧酸、酯、胺和腈。

2. The Unique Nature of Carbon | 碳的独特性质

Carbon has four valence electrons, so it forms four covalent bonds to achieve a stable octet. This gives rise to straight chains, branched structures and ring systems.

碳有四个价电子，因此形成四个共价键以达到稳定八隅体。这产生了直链、支链结构和环状体系。

The C–C bond is relatively strong and unreactive compared with many other single bonds. This makes carbon skeletons stable enough to support a huge number of different compounds.

碳-碳键与其他许多单键相比相对较强且不活泼。这使得碳骨架足够稳定，能够支撑数量庞大的不同化合物。

Carbon can form single, double and triple bonds, as seen in alkanes, alkenes and alkynes. It can also bond to electronegative atoms such as oxygen and nitrogen, creating polar functional groups that control reactivity.

碳可以形成单键、双键和三键，如烷烃、烯烃和炔烃中所示。它也可以与氧和氮等电负性原子成键，形成控制反应活性的极性官能团。

• Four bonding regions give a tetrahedral shape with 109.5° bond angles.
• Three bonding regions give a trigonal planar shape with 120° bond angles.
• Two bonding regions give a linear shape with 180° bond angles.

• 四个成键区域产生键角为 109.5° 的四面体形。
• 三个成键区域产生键角为 120° 的平面三角形。
• 两个成键区域产生键角为 180° 的直线形。

3. Representing Organic Molecules | 有机分子的表示方法

A molecular formula shows the actual number of atoms of each element, for example C₂H₆O. It does not show how the atoms are connected.

分子式表示每种元素原子的实际数目，例如 C₂H₆O。它不显示原子如何连接。

A structural formula shows the arrangement of atoms in a molecule, often using condensed forms such as CH₃CH₂OH. A displayed formula shows every atom and every bond.

结构式显示分子中原子的排列，常使用缩合形式，例如 CH₃CH₂OH。展示式显示每个原子和每条键。

A skeletal formula uses lines and vertices, with carbon atoms implied at the ends and junctions of lines. Hydrogen atoms attached to carbon are usually not shown in skeletal formulae.

骨架式使用线段和顶点，碳原子隐含在线段端点和交点处。与碳相连的氢原子在骨架式中通常不显示。

• Molecular formula: C₂H₆O
• Structural formula: CH₃CH₂OH
• Displayed formula: every atom and bond drawn
• Skeletal formula: only the carbon skeleton and functional groups shown

• 分子式：C₂H₆O
• 结构式：CH₃CH₂OH
• 展示式：画出每个原子和每条键
• 骨架式：仅显示碳骨架和官能团

4. Functional Groups and Homologous Series | 官能团与同系物

A functional group is an atom or group of atoms responsible for the characteristic reactions of a compound. For example, the –OH group makes alcohols, and the C=C group makes alkenes.

官能团是决定化合物特征反应的原子或原子团。例如，–OH 基团形成醇，C=C 基团形成烯烃。

A homologous series is a family of compounds with the same functional group, a common general formula, and each member differs from the next by a CH₂ unit. Members show gradual trends in physical properties but similar chemical properties.

同系物是一类具有相同官能团、共同通式、相邻成员相差一个 CH₂ 单元的化合物。同系物的物理性质呈现渐变趋势，但化学性质相似。