Ch. 4

Question 1

Where is the electron in a free radical?

Answer 1

The p orbital

Question 2

Initiation

Answer 2

Make radicals from nonradicals

Question 3

Propagation

Answer 3

Radical reacts with nonradical

Question 4

Termination

Answer 4

Two radicals react to form nonradicals

Question 5

Keq (products and reactants)

Answer 5

[products]. [C]c[D]d
= —————– = ————
[reactants]. [A]a[B]b

Question 6

What is ∆G

Answer 6

the amount of energy available to do work; energy of products - energy of reactants

Question 7

∆G formula

Answer 7

∆Gº = -RT(lnKeq); ∆Gº = ∆Hº - T∆Sº

Question 8

Enthalpy

Answer 8

Change in bonding energy

Question 9

Entropy

Answer 9

Change in disorder

Question 10

Do cyclic molecules or acyclic molecules have more entropy?

Answer 10

Acyclic because cyclic molecules have restricted bond rotation

Question 11

What does ∆E equal to

Answer 11

∆Gº

Question 12

Bond dissociation ________ energy, bond formation ________ energy

Answer 12

requires, releases

Question 13

Homolytic cleavage

Answer 13

When the bond breaks, each atom gets one electron

Question 14

Heterolytic cleavage

Answer 14

When the bond breaks, the most electronegative gets both electrons

Question 15

What range do most BDE fall between

Answer 15

60-100 kcal/mol

Question 16

Rate law equation (for A+B –> C + D)

Answer 16

rate = kr[A]a[B]b

Question 17

What is order

Answer 17

Order is the number of molecules of that reactant which is present in the rate-determining step of the mechanism

Question 18

Rate constant formula

Answer 18

kr = Ae^(-Ea/RT)

Question 19

What is activation energy

Answer 19

the minimum kinetic energy needed to react

Question 20

What is the value of R (gas constant)

Answer 20

8.314 J/Kmol

Question 21

Intermediates

Answer 21

Short-lived species on the way to a product

Question 22

Transition states

Answer 22

the highest point in energy between two chemicals

Question 23

Rate Determining Step

Answer 23

The slowest step in the reaction will have the highest energy transition state

Question 24

With ____ Ea, rate decreases

Answer 24

increasing

Question 25

With ______ temperature, rate increases

Answer 25

increasing

Question 26

_______ reacts explosively

Answer 26

Fluorine

Question 27

_____ must be heated to react

Answer 27

Bromine

Question 28

_______ reacts at a moderate rate

Answer 28

Chlorine

Question 29

_______ does not detectibly react

Answer 29

Iodine

Question 30

Is a tertiary radical or primary radical more stable

Answer 30

tertiary

Question 31

With increasing degree, dissociation energy gets ________

Answer 31

weaker

Question 32

What does it mean that bromination is highly selective

Answer 32

Prefers tertiary over secondary over primary

Question 33

In an endothermic reaction the transition state resembles the _____; in an exothermic reaction, the transition state resembles the _________.

Answer 33

product; reactant

Question 34

Hammond Postulate

Answer 34

Transition state looks like what it is closest in energy to

Question 35

Bromination is exo/endo thermic, Chlorination is exo/endo thermic

Answer 35

Bromination: endo
Chlorination: exo

Question 36

Bromination has a _______ difference in Ea, Chlorination has a ______ difference in Ea

Answer 36

large, small

Question 37

What degree carbocation is most stable

Answer 37

tertiary

Question 38

What are the two ways carbocations are stabalized by alkyl substituents

Answer 38

Inductive effect, hyperconjugation

Question 39

Inductive effect

Answer 39

Donation of electron density along the sigma bonds

Question 40

Hyperconjugation

Answer 40

Overlap of sigma bonding orbitals with empty p orbitals

Question 41

Carbanions

Answer 41

Eight electrons: six bonding, one lone pair
Negative charge
Nucleophilic and basic

Question 42

What degree is most stable for carboanions

Answer 42

Methyl, then primary

Question 43

Carbenes

Answer 43

Have a neutral carbon
Vacant p orbital, so it can react as an electrophile
Has a lone pair in the sp2 orbital so it can react as a nucleophile