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19.21 : Amines to Alkenes: Hofmann Elimination

Alkenes can be obtained from amines via an E2 elimination. The amine is first converted into a good leaving group, such as a quaternary ammonium salt. This is accomplished by treating the amine with an excess of alkyl halide, which results in a halide salt. Next, the halide salt is transformed into a hydroxide salt that functions as a base to enable elimination.

Under thermal conditions, the hydroxide can abstract a proton from the β carbon; this generates an alkene with the simultaneous release of a neutral amine molecule. This elimination process is called the Hofmann elimination. For the elimination to occur, the β proton and tertiary amine group must be positioned opposite or anti-periplanar to each other. This reaction yields the less substituted alkene as the major product, also known as the Hofmann product.

Tags
Hofmann EliminationAminesAlkenesE2 EliminationQuaternary Ammonium SaltAlkyl HalideHydroxide SaltcarbonAnti periplanarHofmann ProductLess Substituted Alkene

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19.21 : Amines to Alkenes: Hofmann Elimination

Amines

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19.1 : Amines: Introduction

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19.2 : Nomenclature of Primary Amines

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19.3 : Nomenclature of Secondary and Tertiary Amines

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19.4 : Nomenclature of Aryl and Heterocyclic Amines

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19.5 : Structure of Amines

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19.6 : Physical Properties of Amines

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19.7 : Basicity of Aliphatic Amines

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19.8 : Basicity of Aromatic Amines

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19.9 : Basicity of Heterocyclic Aromatic Amines

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19.10 : NMR Spectroscopy Of Amines

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19.11 : Mass Spectrometry of Amines

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19.12 : Preparation of Amines: Alkylation of Ammonia and Amines

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19.13 : Preparation of 1° Amines: Azide Synthesis

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19.14 : Preparation of 1° Amines: Gabriel Synthesis

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