Radical Reaction

Question 1

Homolytic Bond Cleavage

Answer 1

Breaks a bond to form two radicals

Question 2

What is the most stable radical?

Answer 2

Tertiary radical where methyl radical is the least stable

Question 3

What is the common pattern for resonance of radicals?

Answer 3

An unpaired electron near a double bond

Question 4

______________ radicals are more stable than tertiary radicals

Answer 4

Resonance Stablized

Question 5

Radicals dont undergo ______________

Answer 5

Radical rearrangment

Question 6

What are the different tpyes of arrow pushing for radicals?

Answer 6

1. Homolytic Cleavage
2. Addition to a double bond
3. Hydrogen Abstraction
4. Halogen Abstration
5. Elimination
6. Coupling

Question 7

Homolytic Cleavage

Answer 7

Requires a large input of energy where the energy can either be heat or light (hv)

Question 8

Addition to a double bond

Answer 8

A radical adds to a double bond thereby destroying the double & forming a single bond

Question 9

Hydrogen addition

Answer 9

A radical can abstract a hydrogen atom from a compound generating a new radical

Question 10

Halogen Abstraction

Answer 10

A radical can abstract a halogen atom generating a rew radical (similar to hydrogen abstraction)

Question 11

Elimination

Answer 11

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

Question 12

Coupling

Answer 12

Two radicals join together & form a bond

Question 13

Usually there are ___ or ___ arrows in a radical mechanism, where the number of arrows correspond to the number of electrons moving

Answer 13

2 or 3

Question 14

What are the 3 phases in a radical reaction ?

Answer 14

1. Initiation
2. Termination
3. Propagation

Question 15

Initiation

Answer 15

When radicals are created

Question 16

Terminiation

Answer 16

When two radicals cancel out each other by forming a bond

Question 17

Propagation

Answer 17

The sum of the propagation step is the overall net reaction

Question 18

What is the mechanism for radical chlorination ?

Answer 18

1. Homolytic cleavage (Inititation)
2. Hydrogen abstraction (Propagation)
3. Halogen abstraction (Propagation)
4. Coupling (Termination)

Question 19

Radical initators

Answer 19

A compound with a weak bond that undergoes homolytic bond cleavage with ease

Question 20

___________ is often used as radical initators because the oxygen - oxygen bond is weak

Answer 20

Acyl Peroxides

Question 21

Radical Inhibitors

Answer 21

A compound that prevents a chain reaction from either getting started or continuing

Question 22

_____ & ____ are radical inhibitor

Answer 22

O₂ & Hydroquinone

Question 23

Radical halogenation of ____ & ______ are only favorable

Answer 23

Br₂ & Cl₂ (Br₂ is slower than Cl₂ but Br₂ is more selective than Cl₂)

Question 24

Halogentation occurs at ____________ when using Br₂ but doesn’t matter when using Cl₂

Answer 24

More substitited Position

Question 25

When a reagent such as Br₂ are least reactive they are usually the \_\_\_\_\_\_\_\_\_\_

Answer 25

Most selective

Question 26

What is the sterochemistry with halogenation of radicals?

Answer 26

The sterochemistry is unknown where there is a racemic mixture

Question 27

Allylic Bromination

Answer 27

When the Br is added to the allylic position

Question 28

To avoid competition between allylic bromination & ionic addition of Br₂ on a double bond _________________ is used as a reagent istead of Br₂

Answer 28

N-Bromosuccinimide (NBS)

Question 29

Hydrofluorocarbons (HFCs)

Answer 29

Are compounds that contain only carbon , flourine, & hydrogen

Question 30

What is the mechanism for Autooxidation?

Answer 30

1. Hydrogen abstraction (Initiation) 2. Coupling (Propagation) 3. Hydrogen abstraction (Propagation) 4. Coupling (Termination)

Question 31

Antioxidants

Answer 31

One molecule of a radical scavenger (inhibitor) can prevent the autooxidation of thousands of oil molecules

Question 32

What are the common types of Antioxidants?

Answer 32

BHT & BHA

Question 33

What is the mechanism for Anti-Markovnikov addition of HX? (Radical addition of HBr to alkenes)

Answer 33

1. Homolytic cleavage (Initiation) 2. Hydrogen abstraction (Initiation) 3. Addition (Propagation) 4. Hydrogen abstraction (Propagation) 5. Coupling (Termination)

Question 34

An ______________ results in a markovnikov addition

Answer 34

Ionic mechanism

Question 35

A ____________ results in an anti-markonvikov addition

Answer 35

Radical

Question 36

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ can only be accomplished with HBr

Answer 36

Anti-markovnikov addition

Question 37

What is the stereochemsitry for radical addition of HBr?

Answer 37

Unknown has a racemic mixture

Question 38

What is the mechanism for radical polymerzation?

Answer 38

1. Homolytic cleavage (Initiation) 2. Addition (Initation) 3. Addition (Propagation) 4. Coupling (Termination) 5. Coupling (Termination)

Question 39

Cracking

Answer 39

Converts large alkanes to smaller alkanes

Question 40

Hydrocracking

Answer 40

Cracking with H₂ to produce alkanes

Question 41

\_\_\_\_\_\_\_\_\_\_\_\_\_\_ is usually used to add a functional group to an alkane

Answer 41

Bromination