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

Epoxidation of Alkenes (mCPBA) Swern Oxidation Oxidation of Secondary Alcohol to Ketone Claisen Condensation (Ethyl Acetate) Aldol Condensation of Acetaldehyde Kolbe Electrolysis Baeyer-Villiger Oxidation Beckmann Rearrangement (Cyclohexanone Oxime) Catalytic Hydrogenation of Ethylene Dehydration of Ethanol

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.