Intermediate Topic 767 of 1102 Organic Chemistry
Homolytic and Heterolytic Fission
Bond breaking that splits electrons evenly into radicals or unevenly into ions.
In-depth explanation of Homolytic and Heterolytic Fission
Bond breaking can occur in two ways. Homolytic fission splits the shared pair of electrons evenly, giving two neutral radicals, and is favoured in nonpolar bonds under heat or light. Heterolytic fission gives both electrons to one atom, forming a cation and an anion, and occurs most readily in polar bonds and in polar solvents that stabilize the ions. In reaction mechanisms, a fishhook or half-headed curly arrow shows the movement of a single electron in homolysis, while a full arrow shows a pair of electrons in heterolysis.
Going deeper: Homolytic and Heterolytic Fission
Key ideas: Homolysis splits a bond evenly, giving two radicals, favoured by nonpolar solvents, heat or light, and weak bonds (the O-O bond of peroxides is about 150 kJ/mol). Heterolysis gives ions, favoured by polar bonds, polar solvents and acids or Lewis acids. Bond dissociation energy refers to homolysis. Use single-headed (fish-hook) arrows for homolysis, double-headed for heterolysis.
Common mistakes and connections: Students use the wrong arrowheads, or assume heterolysis always produces carbocations when carbanion formation is sometimes favoured. Another mistake is using BDE values to predict ionic reaction energies. Links to radical and ionic mechanisms, carbocation stability and solvent polarity.
Visualization of Homolytic and Heterolytic Fission
Heterolytic fission, as in SN1 ionization, splits the bond so both electrons go to one atom giving ions, unlike homolysis, which gives two radicals. The interactive lesson shows this as a live animation or chart.
Worked example and use case
The chlorine molecule breaks by homolysis under ultraviolet light, giving two chlorine radicals.
Frequently asked questions about Homolytic and Heterolytic Fission
What is Homolytic and Heterolytic Fission?
Bond breaking that splits electrons evenly into radicals or unevenly into ions.
Is Homolytic and Heterolytic Fission a beginner, intermediate or advanced topic?
Homolytic and Heterolytic Fission is a intermediate topic in Organic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Homolytic and Heterolytic Fission?
Study these earlier topics in Organic Chemistry first: Carbocations, Carbanions, Carbenes.
What comes after Homolytic and Heterolytic Fission?
The next topics in Organic Chemistry are Electrophiles and Nucleophiles and Reaction Types in Organic Chemistry.
Can I practise Homolytic and Heterolytic Fission with quizzes?
Yes. The interactive lesson includes a self-check question on Homolytic and Heterolytic Fission, and the Organic Chemistry quiz draws on every topic in this area.
Where Homolytic and Heterolytic Fission fits in Organic Chemistry
Homolytic and Heterolytic Fission is topic 39 of 148 in Organic Chemistry.