Radical Reaction Flashcards
Homolytic Bond Cleavage
Breaks a bond to form two radicals
What is the most stable radical?
Tertiary radical where methyl radical is the least stable
What is the common pattern for resonance of radicals?
An unpaired electron near a double bond
______________ radicals are more stable than tertiary radicals
Resonance Stablized
Radicals dont undergo ______________
Radical rearrangment
What are the different tpyes of arrow pushing for radicals?
- Homolytic Cleavage
- Addition to a double bond
- Hydrogen Abstraction
- Halogen Abstration
- Elimination
- Coupling
Homolytic Cleavage
Requires a large input of energy where the energy can either be heat or light (hv)

Addition to a double bond
A radical adds to a double bond thereby destroying the double & forming a single bond
Hydrogen addition
A radical can abstract a hydrogen atom from a compound generating a new radical
Halogen Abstraction
A radical can abstract a halogen atom generating a rew radical (similar to hydrogen abstraction)
Elimination
The position bearing the unparied electron is called the alpha position where in elimination the double bond forms between an alpha & beta position which results in a single bond at the beta position cleaved causing the compound to fragment into two pieces
Coupling
Two radicals join together & form a bond
Usually there are ___ or ___ arrows in a radical mechanism, where the number of arrows correspond to the number of electrons moving
2 or 3
What are the 3 phases in a radical reaction ?
- Initiation
- Termination
- Propagation
Initiation
When radicals are created
Terminiation
When two radicals cancel out each other by forming a bond
Propagation
The sum of the propagation step is the overall net reaction
What is the mechanism for radical chlorination ?
- Homolytic cleavage (Inititation)
- Hydrogen abstraction (Propagation)
- Halogen abstraction (Propagation)
- Coupling (Termination)
Radical initators
A compound with a weak bond that undergoes homolytic bond cleavage with ease
___________ is often used as radical initators because the oxygen - oxygen bond is weak
Acyl Peroxides
Radical Inhibitors
A compound that prevents a chain reaction from either getting started or continuing
_____ & ____ are radical inhibitor
O2 & Hydroquinone
Radical halogenation of ____ & ______ are only favorable
Br2 & Cl2 (Br2 is slower than Cl2 but Br2 is more selective than Cl2)
Halogentation occurs at ____________ when using Br2 but doesn’t matter when using Cl2
More substitited Position
When a reagent such as Br2 are least reactive they are usually the __________
Most selective
What is the sterochemistry with halogenation of radicals?
The sterochemistry is unknown where there is a racemic mixture
Allylic Bromination
When the Br is added to the allylic position
To avoid competition between allylic bromination & ionic addition of Br2 on a double bond _________________ is used as a reagent istead of Br2
N-Bromosuccinimide (NBS)
Hydrofluorocarbons (HFCs)
Are compounds that contain only carbon , flourine, & hydrogen
What is the mechanism for Autooxidation?
- Hydrogen abstraction (Initiation)
- Coupling (Propagation)
- Hydrogen abstraction (Propagation)
- Coupling (Termination)
Antioxidants
One molecule of a radical scavenger (inhibitor) can prevent the autooxidation of thousands of oil molecules
What are the common types of Antioxidants?
BHT & BHA
What is the mechanism for Anti-Markovnikov addition of HX? (Radical addition of HBr to alkenes)
- Homolytic cleavage (Initiation)
- Hydrogen abstraction (Initiation)
- Addition (Propagation)
- Hydrogen abstraction (Propagation)
- Coupling (Termination)
An ______________ results in a markovnikov addition
Ionic mechanism
A ____________ results in an anti-markonvikov addition
Radical
_________________ can only be accomplished with HBr
Anti-markovnikov addition
What is the stereochemsitry for radical addition of HBr?
Unknown has a racemic mixture
What is the mechanism for radical polymerzation?
- Homolytic cleavage (Initiation)
- Addition (Initation)
- Addition (Propagation)
- Coupling (Termination)
- Coupling (Termination)
Cracking
Converts large alkanes to smaller alkanes
Hydrocracking
Cracking with H2 to produce alkanes
______________ is usually used to add a functional group to an alkane
Bromination