Mechanisms - Organic Flashcards
What is heterolytic fission?
Bond breaks unevenly and both electrons from the bond go to one atom.
What is homolytic fission?
Bond breaks evenly and each bonded atom gets one electron, forming free radicals.
Define free radicals.
Species that have an unpaired electron and are highly reactive.
What are the three stages of free-radical substitution reactions?
- Initiation
- Propagation
- Termination
What occurs during the initiation step of free-radical substitution?
U.V. light causes homolytic fission of the halogen molecule, creating two halogen radicals.
What happens during the propagation step of free-radical substitution?
Radical species react with the alkane and get substituted, creating further radicals.
What occurs in the termination step of free-radical substitution?
Two radical species combine to create a covalent bond, terminating the chain.
What is a radical represented by?
A • symbol to show one unpaired electron (e.g. Br•).
What is the definition of electrophilic addition?
A reaction where two reactants form only one product.
What is the significance of the C=C double bond in alkenes?
It is an electron-rich area that is readily attacked by positively charged electrophiles.
What determines the major product in electrophilic addition reactions with asymmetrical alkenes?
The stability of the carbocation formed as an intermediate.
What is the order of stability for carbon carbocations?
Tertiary > secondary > primary.
Define nucleophile.
Something that is attracted to a positive charge.
What is a polar bond?
A bond where one atom is more electronegative than the other, creating a small positive charge.
What happens during a nucleophilic substitution reaction?
A nucleophile attacks the carbon of a carbon-halogen bond, resulting in the substitution of the halogen.
