E2 Elimination (Dehydrohalogenation)
C2H5Br + KOH → C2H4 + KBr + H2O
概述
Strong base (KOH in ethanol) removes a beta-hydrogen and the halide leaves simultaneously in a concerted E2 elimination to form an alkene. The H and Br must be anti-periplanar (180 degrees) for the elimination to proceed. E2 competes with SN2, with bulky bases and secondary/tertiary substrates favoring elimination.
参与者
| 角色 | 物质 | 系数 | 状态 |
|---|---|---|---|
| 反应物 | Potassium Hydroxide KOH | 1 | (aq) |
| 产物 | Ethylene C₂H₄ | 1 | (g) |
| 产物 | Water H₂O | 1 | (l) |
日常示例
E2 elimination is used to prepare alkenes from easily available alkyl halides and is key to understanding organic reaction selectivity.
工业重要性
E2消除反应（及相关的E1消除反应）在药物合成中用于构建烯烃官能团，特别是在合成天然产物和具有特定立体化学的药物分子时。工业上利用卤代烃的碱性消除反应制备乙烯基单体（如氯乙烯热消除制备乙炔替代路线）和其他不饱和化合物。
属性
- 类型
- Organic
- 可逆
- 否
- 能量
- 放热
- ΔH
- -50.0 kJ/mol
相关反应
Swern Oxidation
Oxidation of Secondary Alcohol to Ketone
Claisen Condensation (Ethyl Acetate)
Kolbe Electrolysis
Baeyer-Villiger Oxidation
Beckmann Rearrangement (Cyclohexanone Oxime)
Catalytic Hydrogenation of Ethylene
Condensation Polymerization (Nylon 6,6)
Cope Rearrangement
Epoxidation of Alkenes (mCPBA)
Frequently Asked Questions
What is the equation for E2 Elimination (Dehydrohalogenation)?
The balanced equation is: C₂H₅Br + KOH → C₂H₄ + KBr + H₂O.
What type of reaction is E2 Elimination (Dehydrohalogenation)?
E2 Elimination (Dehydrohalogenation) is a organic reaction.
Is E2 Elimination (Dehydrohalogenation) exothermic or endothermic?
E2 Elimination (Dehydrohalogenation) is exothermic (releases energy). The enthalpy change (ΔH) is -50.0 kJ/mol.