定义Definition
磺化反应是芳烃与浓硫酸或发烟硫酸（SO₃）作用，在芳环上引入磺酸基（–SO₃H）生成芳磺酸的亲电取代反应。与其他亲电取代不同，它是可逆的。
Aromatic sulfonation introduces a sulfonic acid group (–SO₃H) onto an arene with concentrated or fuming sulfuric acid (SO₃) by electrophilic substitution; unlike most such reactions, it is reversible.
机理与可逆性Mechanism and reversibility
亲电试剂是 SO₃（或质子化的 HSO₃⁺）。芳环进攻 S 生成 σ 络合物，失去质子得芳磺酸。在稀酸中加热（水蒸气）可脱磺化，因此磺酸基可作为“占位基团”保护某个位置，之后再除去。
The electrophile is SO₃ (or HSO₃⁺). The ring attacks sulfur, forming a σ-complex that loses a proton. Heating in dilute acid (steam) reverses it, so a sulfonic acid can serve as a removable blocking group.
热力学与动力学控制Thermodynamic versus kinetic control
萘的磺化：80 °C 主要得 1-萘磺酸（动力学产物，反应快），160 °C 主要得 2-萘磺酸（热力学产物，位阻小更稳定）。
Naphthalene sulfonation gives mainly the 1-sulfonic acid at 80 °C (kinetic) and the 2-sulfonic acid at 160 °C (thermodynamic, less hindered).
应用Applications
直链烷基苯磺酸钠（LAS）是最大宗的合成洗涤剂；磺胺类药物、染料中间体、磺化聚苯乙烯离子交换树脂都依赖磺化反应。芳磺酸钠碱熔可制酚（早期工业苯酚法）。
Linear alkylbenzene sulfonates (LAS) are the largest-volume synthetic detergents; sulfa drugs, dye intermediates and sulfonated-polystyrene ion-exchange resins rely on sulfonation. Alkali fusion of sulfonates once made phenol industrially.
反应Reactions
浓硫酸或发烟硫酸，加热；脱磺化：稀 H₂SO₄ + 水蒸气
Concentrated or fuming H₂SO₄ with heating; desulfonation with dilute acid and steam
SO₃ 作为亲电试剂。
SO₃ acts as the electrophile.
芳环进攻生成 σ 络合物。
The ring attacks to form a σ-complex.
失去 H⁺ 得芳磺酸。
Loss of H⁺ gives the sulfonic acid.
苯磺化。
Sulfonation of benzene.
反应机理图Mechanism
红色弯箭头表示一对电子的移动方向：从电子来源（孤对电子或化学键）指向电子去向。Red curly arrows show where an electron pair moves: from its source (lone pair or bond) to its destination.
苯环进攻 SO₃ 的硫原子
The ring attacks the sulfur of SO₃
HSO₄⁻ 夺取质子，恢复芳香性
HSO₄⁻ removes the proton, restoring aromaticity
苯磺酸根
Benzenesulfonate
苯磺酸；反应可逆，稀酸加热可脱磺酸基
Benzenesulfonic acid; reversible — hot dilute acid removes the group
年表Timeline
- 1834
米切利希制得苯磺酸
Mitscherlich prepares benzenesulfonic acid
- 1930s
烷基苯磺酸盐洗涤剂问世
Alkylbenzene sulfonate detergents appear