chapter 4

Question 1

Thermodynamics: study of _______ changes that accompany chemical and physical transormations

Answer 1

energy

Question 2

Kinetics: study of reaction _______

Answer 2

rates

Question 3

a complete mechanism accounts for ______ reactancts used and _____ products formed

Answer 3

all
all

Question 4

Radicals are _______ intermediates that have a(n) _______ number of electrons

Answer 4

reactive
odd

Question 5

What are the 3 steps to a chain reaction mechanism?

Answer 5

1) initiation
2) propagation
3) termination

Question 6

What is initiation composed of?

Answer 6

creating radicals using heat or light

Question 7

What is propagation composed of?

Answer 7

radical + normal molecule
Two steps with the radical product from step 1 being the radical reactant in step 2

Question 8

What is termination composed of?

Answer 8

radical + radical
mix the radicals together

Question 9

Radical + radical reactions are _______

Answer 9

rare

Question 10

While a chain reaction is in progress, the concentration of radicals is _______. The probability that two radicals will combine in a termination step is _______ than the probability that each radical will encounter a molecule of reactant and give a propagation step

Answer 10

low
lower

Question 11

The termination step is more important at the _______ of the reaction when the free radicals are _______ likely to encounter another free radical. The chain reaction quickly stops

Answer 11

end
more

Question 12

Keq (equilibrium constant) tells us the position of the equilibrium.
Keq>1 _______ reaction favored (______)
Keq<1 _______ reaction favored (______)

Answer 12

forward (products)
reverse (reactants)

Question 13

Gibbs Free energy: change in _______ of a reaction. Can be calculated from Keq

Answer 13

free energy

Question 14

A reaction with a _______ ΔG (_______) is favorable and spontaneous

Answer 14

negative (exergonic)

Question 15

A reaction with a _______ ΔG (_______) is unfavorable because energy must be added to the system

Answer 15

positive (endergonic)

Question 16

What are the 2 factors that contribute to change in free energy?

Answer 16

1) entropy (ΔS)
2) enthalpy (ΔH)

Question 17

Entropy is the increase in the _______ of the system

Answer 17

disorder

Question 18

Processes with an _______ in entropy are favored

Answer 18

increase (+ΔS)

Question 19

Enthalpy is the heat _______ or _______ during a chemical reaction at standard conditions. All about bond _______!!!!!

Answer 19

released or absorbed
strength

Question 20

An _______ reaction is the reaction when a weak bond is broken and a strong bond is formed

Answer 20

exothermic

Question 21

_______ is the reaction when a strong bond is broken and a weak bond is formed

Answer 21

endothermic

Question 22

Bond strength is a measure of the heat change that occurs on breaking a bond, known as ________

Answer 22

bond dissociation energy

Question 23

What is the formula for enthalpy changes?

Answer 23

(BDE of bonds broken) - (BDE of bonds formed)

Question 24

Rate law works with the relationship between the concentrations of the _______ and the observed reaction rate. It can only be determined _______

Answer 24

reactants
experimentally

Question 25

Molecules must have enough _______ to get over an activation barrier (Ea)

Answer 25

energy

Question 26

formula for Overall order of reaction

Answer 26

add all orders

Question 27

The activation energy (Ea) represents the energy difference between the reactants and the _______

Answer 27

transition state

Question 28

In a reaction-energy diagram, the low points are _______, _______, and _______

Answer 28

reactants, intermediates, and products

Question 29

In a reaction-energy diagram, the high points are _______

Answer 29

transition states

Question 30

The rate-limiting step (r.d.s) is determined by the highest _______

Answer 30

activation energy (Ea)

Question 31

Hammond's postulate: the structure of the _______ resembles the structure of the closest stable structure (reactants or products) in _______

Answer 31

transition state energy

Question 32

Chlorination shows _______ radical selectivity. This is because of the preference for the primary radical and the secondary radical

Answer 32

poor

Question 33

a __° H is connected to a 1° carbon a __° H is connected to a 2° carbon a __° H is connected to a 3° carbon

Answer 33

1 2 3

Question 34

What is the term for a radical that is one away from an aromatic ring?

Answer 34

benzylic

Question 35

What is the term for a radical that is one away from a double bond?

Answer 35

allylic

Question 36

Bromination requires _______ conditions (hv and high temperature) compared to chlorination - the reaction is _______

Answer 36

harsher endothermic

Question 37

Why is bromination more selective than chlorination?

Answer 37

Hammond's postulate (the transition state is closer in energy to the products), so the bond between H and Br is closer to happening

Question 38

Reactive intermediates are _______ species that react with another species as quickly as they are formed

Answer 38

short-lived

Question 39

What are the 3 types of reactive intermediates in order of their stability? (from least to most)

Answer 39

1) carbocation 2) radical 3) carbanion

Question 40

carbocation has __ nonbonding electrons and a _____ charge

Answer 40

0 positive

Question 41

Alkyl groups (-R) are _______, and they help stabilize an electron-deficient carbocation in 2 ways:

Answer 41

EDG's 1) inductive 2) hyperconjugation

Question 42

Carbocation stability is _______ stable with more R groups If they have the same amount of R groups then compare _______

Answer 42

more resonance

Question 43

_______: overlap of filled orbitals on an adjacent alkyl group with the vacant p orbital of a cation

Answer 43

hyperconjugation

Question 44

Free radicals: ___ nonbonding electron(s), _______ charge

Answer 44

1 no

Question 45

radical stability depends on the _______ of the carbon then compare _______

Answer 45

degree resonance

Question 46

Carbanions: ___ nonbonding electron(s), _____ charge

Answer 46

2 negative

Question 47

What are the 2 ways carbanions are stabilized by EWG's?

Answer 47

1) inductive effect 2) resonance

Question 48

Carbanion stability is _______ stable with more R groups If they have the same amount of R groups, then compare _______

Answer 48

less resonance

Question 49

Carbenes: ___ nonbonding electrons, _______ charge CH2 is called a _______ group

Answer 49

2 no methylene

Question 50

What are the axis labels in an energy diagram? (2)

Answer 50

1) energy (y-axis) 2) reaction coordinate (x-axis)