Ch 3: Reactions of Alkanes

Question 1

Heterolytic Cleavage

Answer 1

Produces Cation and Anion

Question 2

Homolytic Cleavage

Answer 2

Produces two Radicals

Question 3

Bond Dissociation Energy (BDE)

Answer 3

Energy required for Homolytic Cleavage

Question 4

What factors affect BDE?

Answer 4

Atomic Size, Orbital Energy, Stability of the Radicals

Question 5

How does Atomic Size affect BDE?

Answer 5

Bigger Atom = Lower BDE
Electrons further from the nucleus are easier to remove

Question 6

How does Orbital Energy affect BDE?

Answer 6

Higher Orbital Energy = Higher BDE
Higher energy orbitals are less stable and easier to break

Question 7

How does the stability of the Radicals affect BDE?

Answer 7

More Stable Radicals = Lower BDE
Reaction favors more stable products

Question 8

What is the Relative Stability of Carbon Radicals?

Answer 8

3’ > 2’ > 1’ > CH3

Question 9

What are the four steps of Radical Halogenation?

Answer 9

Initiation, Propagation 1 (PS1) , Propagation 2 (PS2) , Termination

Question 10

Initiation of Radical Halogenation

Answer 10

Homolytic Cleavage of X-X

Question 11

Propagation 1 of Radical Halogenation

Answer 11

Homolytic Cleavage of the C-H bond and Formation of H-X

Question 12

Propagation 2 of Radical Halogenation

Answer 12

Homolytic Cleavage of X-X and Formation of C-X Bond

Question 13

Termination of Radical Halogenation

Answer 13

Formation of X-X from X Radicals
OR
Formation of C-X Bond from X Radical
OR
Formation of C-C Bond

Question 14

Radical Monochlorination of Methane Mechanism

Answer 14

Initiation: Homolytic Cleavage of Cl-Cl

PS1: Homolytic Cleavage of H3C-H and Formation of H-Cl

PS2: Homolytic Cleavage of Cl-Cl and Formation of H3C-Cl

Termination: Formation of Cl-Cl
OR Formation of H3C-Cl from Cl Radical
OR Formation of H3C-CH3

Question 15

Relative Reactivity of Carbons to Monochlorination
3 : 2 : 1

Answer 15

5 : 4 : 1