Chapter 10: Radicals

What is the geometry of radical carbons?

Trigonal planar?

What happens in homolytic cleaveage?

Each electron in a bond goes to one atom, creating radicals

What happpens in radical addition to a pi bond?

One electron from pi bond bonds with radical electron and radical forms on the other side of the pi bond

What happens in hydrogen abstraction?

Halogen radical binds to hydrogen and makes an alkyl radical

What happens in halogen abstraction?

alkyl radical abstracts halogen from molecular halogen and creates another halogen radical

What happens in radical elimination?

Radical position forms a double bond and compound fragments with a new radical

What happens in coupling?

Two radicals form a bond

What happens in initiation of radical methane chlorination?

Homolytic cleavage of molecular chlorine

What happens in propagation of radical methane chlorination?

Hydorgen abstraction by chlorine radical then halogen abstraction of molecular chlorine by methyl radical

What happens in termination of radical methane chlorination?

Coupling between chlorine radicals, between chlorine radicals and methyl radicals, and between methyl radicals.

What happens when xs Cl2 is used in radical chlorine halogenation?

polychlorination

How does homolytic cleavage of Cl2 occur?

Thermal initiation

How can thermal initiation occur at a moderate temperature rather than a very high one?

Radical initiators like alkyl/acyl peroxides

What is an example of a radical inhibitor and how?

O2, couples with radicals

What does hydroquinone do?

Eliminates a radical through hydrogen abstraction, remaining radical is resonance-stabilized.

Why is chlorine typically used in radical halogenation of methane?

Radical bromination is a much slower reaction than radical chlorination, much higher activation energy.

What determines the product distribution of radical halogenation?

Number of hydrogen atoms at each position

What is the rate-determining step in radical halogenation?

Hydrogen abstraction

What is the stereochemistry of radical halogenation?

Racemic mixture obtained when a new chiral center is created

What happens in intiation of radical anti-Markovnikov addition of HBr?

Homolytic cleavage of alkyl peroxide followed by hydrogen abstraction of HBr by radical alkoxide, creating a bromine radical

What happens in the first part of propagation in radical anti-Markovnikov addition of HBr?

Bromine radical binds with an electron from a pi bond and bind at the less substituted position so that a more stable carbon radical forms

What happens in the second part of propagation in radical anti-Markovnikov addition of HBr?

Radical carbon abstracts a hydrogen from HBr, leaving a bromine radical

What happens in termination of radical anti-Markovnikov addition of HBr?

Coupling of bromine radicals