Theoretical principles 理论原则

1. Bonding of the carbon atom. 碳原子的结合。

Electronic structure of the carbon atom is 1s2 2s2 2px1 2py1.

碳原子的电子结构是1s2 2s2 2px1 2py1。

The outer electrons are located in orbitals (volumes of electron probability) having the following shapes 外层电子位于具有以下形状的轨道（电子概率的体积）中:

Carbon is unable to take part in ionic bonding since it is not energetically possible to form either C4+ or C4-. It must therefore bond covalently by sharing electrons.

To achieve its maximum valency of 4. The 2s electrons must become uncoupled to give the electronic structure: 2s1 2px1 2py1

碳不能参与离子键，因为它在能量上不可能形成C4+或C4-。因此，它必须通过分享电子来进行共价键。

为了达到4的最大化合价，2S电子必须解耦，以获得电子结构：2S1 2px1 2py1

During bonding the 2s and 2p orbitals blend together to form four identical orbitals. This process is known as hybridisation.

在结合过程中，2S和2P轨道混合在一起，形成四个相同的轨道。这个过程被称为杂化。

2. Reactions of covalent bonds 共价键的反应

For any organic reaction to take place, covalent bonds must be broken. The factors influencing bond breaking are 要发生任何有机反应，必须打破共价键。影响断键的因素有:

a) Kinetic factors 动力因素

For bond breaking to occur, the molecules must possess a certain amount of energy (activation energy). Sufficient energy may be obtained through collisions with other molecules and transfer of kinetic energy to the bond.

Increasing the temperature of the reaction increases the number of molecules with energies in excess of the activation energy, a rise of about 10oC doubles the rate of reaction.

为使断键发生，分子必须拥有一定的能量（活化能）。足够的能量可以通过与其他分子的碰撞和动能向键的转移获得。

提高反应的温度会增加能量超过活化能的分子数量，上升约10oC，反应速度就会增加一倍。

b) Equilibrium of reactions 反应的平衡性

The reaction must have a favourable equilibrium constant.

该反应必须有一个有利的平衡常数。

3. Mechanism of bond breaking and making 断裂和生成键的机制

A covalent bond can be broken in two ways 一个共价键可以通过两种方式断裂:

a) Homolytic fission 同质裂变

• A:B → Ao + Bo

Produces free radicals which have an unpaired electron and are very reactive.

产生自由基，自由基有一个未配对的电子，非常活跃。

b) Heterolytic fission 异质裂变

• A:B → A+ + B-

• A:B → A- + B+

Produces ions.

产生离子。

4. Bond polarity 键的极性

Many organic molecules possess a dipole moment, due to an unequal distribution of electrons in the molecule. This occurs because some atoms tend to attractor repel electrons.

许多有机分子拥有偶极矩，这是由于分子中的电子分布不均。出现这种情况是因为一些原子倾向于吸引或排斥电子。

Consider the molecule, CH3Cl.

考虑一下分子， CH3Cl

Chlorine has a greater share of the electrons due to the electronegativity it possesses 由于氯气所具有的电负性，它拥有更大的电子份额:

This kind of bond polarisation is known as the inductive effect.

这种键的极化被称为感应效应。

The inductive effect is the power of an atom or group of atoms to attract electrons compared to the power of a hydrogen atom.

感应效应是指与氢原子的力量相比，一个原子或一组原子吸引电子的力量。

NO2 > Cl > I > NH3 > C-H < CH3 C2H5 < (CH3)2CH

Groups which are attracting electrons have a negative inductive (-I) effect. They give rise to electron deficient atoms Cδ+.

Groups which are electron repelling have a positive inductive (+I) effect. They give rise to electron rich carbon atoms Cδ-.

吸引电子的基团具有负的感应作用（-I）。它们会产生缺电子的原子Cδ+。

驱赶电子的基团具有正的感应作用（+I）。它们会产生富含电子的碳原子Cδ-。