Chapter 8.5: Mechanism of Halogenation of Alkanes

Question 1

Define chain initiation

Answer 1

a step in a chain reaction characterized by the formation of reactive intermediates from nonradical or noncharged molecules

Question 2

Define chain length

Answer 2

the number of times the cycle of chain propagation steps repeats in a chain reaction

Question 3

What is the structure of the transition state for an exothermic step looks more like the reactants of that step than the products. Conversely, the structure of the transition state for an endothermic step looks more like the products of that step than the reactants.?

Answer 3

Hammond’ Postulate

Question 4

Describe the radical chain mechanism

Answer 4

Step 1: Chain Initiation
 Chain initiation involves formation of radicals from nonradical species. Dissociated by heat or light.
Step 2: Chain Propagation
 Chain propagation involves reaction of a radical and a molecule to form a new radical
Step 3: Chain Termination
Chain termination involves destruction of radicals. The first three possible chain termination steps involve coupling of radical to form a new covalent bond. The fourth chain termination step, called disproportionation, involves transfer of a hydrogen atom from the beta position of one radical to another radical and formation of an alkane and an alkene

Question 5

What are compounds with one or two carbons, chlorine, and fluorine, formerly used as refrigerants?

Answer 5

chlrofluorocarbons (CFCs)

Question 6

Define chain propagation

Answer 6

a step in a chain reaction characterized by the reaction of a reactive intermediate and a molecule to give a new reactive intermediate and a new molecule

Question 7

Define chlorofluorocarbons (CFCs)

Answer 7

compounds with one or two carbons, chlorine, and fluorine, formerly used as refrigerants

Question 8

Define Hammond’s Postulate

Answer 8

the structure of the transition state for an exothermic step looks more like the reactants of that step than the products. Conversely, the structure of the transition state for an endothermic step looks more like the products of that step than the reactants.

Question 9

Define chain termination

Answer 9

a step in a chain reaction that involves destruction of reactive intermediates

Question 10

What is a step in a chain reaction that involves destruction of reactive intermediates?

Answer 10

chain termination

Question 11

What is a step in a chain reaction characterized by the formation of reactive intermediates from nonradical or noncharged molecules?

Answer 11

chain initiation

Question 12

What is the number of times the cycle of chain propagation steps repeats in a chain reaction?

Answer 12

chain length

Question 13

What is a step in a chain reaction characterized by the reaction of a reactive intermediate and a molecule to give a new reactive intermediate and a new molecule?

Answer 13

chain propagation