📚 AQA A-Level Chemistry 3.11 Amines: Structure, Basicity and Reactions | AQA A-Level 化学 3.11 胺：结构、碱性与反应
Amines are organic derivatives of ammonia in which one or more hydrogen atoms have been replaced by alkyl or aryl groups. This topic underpins many organic synthesis routes and biological molecules, so AQA expects confident use of structures, names, basicity comparisons and key preparation and reaction equations.
胺是氨的有机衍生物，其中一个或多个氢原子被烷基或芳基取代。本专题是许多有机合成路线和生物分子的基础，因此 AQA 要求熟练书写结构式、命名、比较碱性强弱，并掌握关键的制备和反应方程式。
1. Introduction and Classification | 胺的定义与分类
Amines are derived from ammonia, NH₃, by replacing one, two or all three hydrogen atoms with organic groups. They are classified according to the number of organic groups directly bonded to the nitrogen atom.
胺由氨 NH₃ 衍生而来，用一个、两个或全部三个有机基团取代氢原子。它们根据直接与氮原子相连的有机基团数目进行分类。
Primary amines have one organic group attached, secondary amines have two, and tertiary amines have three. The naming of primary, secondary and tertiary amines is based on the number of carbon-containing substituents on nitrogen, not on the degree of alkyl chain branching.
伯胺上连有一个有机基团，仲胺连有两个，叔胺连有三个。伯、仲、叔胺的划分依据是氮上含碳取代基的数目，而不是烷基链的支化程度。
For example, CH₃NH₂ is a primary amine, (CH₃)₂NH is a secondary amine, and (CH₃)₃N is a tertiary amine.
例如，CH₃NH₂ 是伯胺，(CH₃)₂NH 是仲胺，(CH₃)₃N 是叔胺。
2. Nomenclature | 胺的命名
Simple primary amines are named by adding '-amine' to the alkyl group name: methylamine, ethylamine and phenylamine. In systematic IUPAC nomenclature, they may be called methanamine, ethanamine and benzenamine, but AQA commonly uses methylamine, ethylamine and phenylamine.
简单伯胺的命名是在烷基名称后加 '-amine'：methylamine、ethylamine 和 phenylamine。在系统 IUPAC 命名中，它们可称为 methanamine、ethanamine 和 benzenamine，但 AQA 通常使用 methylamine、ethylamine 和 phenylamine。
When an amine has substituents on nitrogen, the prefix N- is used to show the group is attached to the nitrogen atom. For example, CH₃NHCH₂CH₃ is N-methylethylamine.
当氮原子上连有取代基时，用前缀 N- 表示该基团连接在氮原子上。例如 CH₃NHCH₂CH₃ 称为 N-甲基乙胺。
3. Shape and Bonding | 分子形状与成键
In ammonia and amines, the nitrogen atom has three bonding pairs and one lone pair. Electron-pair repulsion gives a trigonal pyramidal shape, with bond angles of approximately 107° in ammonia and similar values in simple amines.
在氨和胺中，氮原子有三对成键电子和一对孤对电子。电子对互斥使分子呈三角锥形，氨的键角约为 107°，简单胺的键角也相近。
The lone pair is essential to amine chemistry: it can form a dative covalent bond to H⁺ or attack electron-poor carbon centres in nucleophilic reactions.
孤对电子对胺的化学性质至关重要：它能与 H⁺ 形成配位共价键，也可以在亲核反应中进攻缺电子的碳中心。
4. Basicity of Amines | 胺的碱性
Amines are weak Bronsted-Lowry bases because the lone pair on nitrogen can accept a proton. For example, methylamine reacts reversibly with water:
胺是弱的 Bronsted-Lowry 碱，因为氮上的孤对电子可以接受质子。例如，甲胺与水发生可逆反应：
CH₃NH₂ + H₂O ⇌ CH₃NH₃⁺ + OH⁻
The equilibrium lies to the left, so amines are weak bases and their aqueous solutions are only slightly alkaline.
平衡偏向左侧，因此胺是弱碱，其水溶液仅呈弱碱性。
5. Comparing Base Strength | 碱性强弱比较
Aliphatic primary amines are generally stronger bases than ammonia. The alkyl group has a positive inductive effect: it releases electron density towards nitrogen, making the lone pair more available for protonation.
脂肪族伯胺通常比氨的碱性更强。烷基具有正的诱导效应：它将电子密度推向氮原子，使孤对电子更容易结合质子。
Phenylamine is a much weaker base than ammonia or aliphatic amines. The lone pair on nitrogen is delocalised into the benzene ring π system, so it is less available to accept a proton.
苯胺的碱性远弱于氨和脂肪族胺。氮上的孤对电子离域进入苯环的 π 体系，因此不易结合质子。
The order of base strength commonly expected by AQA is: primary aliphatic amines > ammonia > phenylamine.
AQA 通常要求掌握的碱性强弱顺序为：脂肪族伯胺 > 氨 > 苯胺。
Secondary and tertiary aliphatic amines also show inductive donation, but aqueous base strength is affected by solvation effects; AQA focuses mainly on primary aliphatic amines being stronger than ammonia
Published by TutorHao | A-Level Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图