16.7 : Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.
Conjugated dienes react with halogens in a similar manner. However, in addition to the 1,2-dihalide, they also form a 1,4-dihalide. The mechanism involves two steps.
First, a nucleophilic attack by one of the diene π bonds on the electrophilic center of the polarized halogen molecule forms a halonium ion intermediate. This is followed by a nucleophilic attack of the displaced halide ion at C2 of the intermediate to give the 1,2-product or at C4 to form the 1,4-addition product. The ratio of the products formed depends on the reaction temperature. Low temperature favors the 1,2-product, whereas high temperature favors the 1,4-product.
From Chapter 16:
Now Playing
16.7 : Electrophilic 1,2- and 1,4-Addition of X<sub>2</sub> to 1,3-Butadiene
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
2.1K Views
16.1 : Structure of Conjugated Dienes
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
2.9K Views
16.2 : Stability of Conjugated Dienes
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
2.9K Views
16.3 : π Molecular Orbitals of 1,3-Butadiene
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
6.6K Views
16.4 : π Molecular Orbitals of the Allyl Cation and Anion
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
3.7K Views
16.5 : π Molecular Orbitals of the Allyl Radical
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
3.0K Views
16.6 : Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
3.4K Views
16.8 : Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
2.2K Views
16.9 : UV–Vis Spectroscopy of Conjugated Systems
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
5.9K Views
16.10 : UV–Vis Spectroscopy: Woodward–Fieser Rules
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
20.6K Views
16.11 : Pericyclic Reactions: Introduction
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
4.4K Views
16.12 : Thermal and Photochemical Electrocyclic Reactions: Overview
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
2.1K Views
16.13 : Thermal Electrocyclic Reactions: Stereochemistry
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
1.7K Views
16.14 : Photochemical Electrocyclic Reactions: Stereochemistry
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
1.6K Views
16.15 : Cycloaddition Reactions: Overview
Dienes, Conjugated Pi Systems, and Pericyclic Reactions
2.2K Views
See More
ABOUT JoVE
Copyright © 2025 MyJoVE Corporation. All rights reserved