Test Bank for Organic Chemistry, 4th Edition by David R. Klein
9781119659594 | All Chapters with Answers and Rationals
What type of bond cleavage must occur to generate radicals? - ANSWER: Homolytic
How must we adjust our curved arrows to account for the formation of radicals? - ANSWER: We need
fishhooks
How many hydrogens at the indicated carbon? Hybridization? In which orbital is the radical? 11001 -
ANSWER: 1, sp^2, p 11002
What's the order of stability of radicals? (By substitution) - ANSWER: 3° > 2° > 1°
Which of the following C-H bonds will be easiest to homolytically cleave? Why? 11003 - ANSWER:
11003. C-Hc. Because it's the weakest (has the lowest potential energy difference from bonded to
not-bonded because the radical is most stable as 3º
Draw the resonance arrows to stabilize the allylic anion. 11004 - ANSWER: 11005
Draw the resonance arrows to stabilize the allylic radical 11006 - ANSWER: 11007
Which of the following C-H bonds will be easiest to homolytically cleave? 11008 - ANSWER: C-Hd
because its resultant radical is most stable - more stable than C-Hc's resultant radical - because it is
secondary with resonance (which is more stable than tertiary without resonance)
What's the most stable radical? (Structurally) - ANSWER: 2º allylic because it is secondary with
resonance.
What are the parts of radical reactions? - ANSWER: 1. Initiation. 2. Propagation. 3. Termination.
If an alkane and Cl2 react, several potential bonds could homolytically break. Which is the easiest
bond to break? What does this implicate. - ANSWER: Cl-Cl. They have the lowest dissociation energy
(243 kJ/mol) maybe because they're somewhat large (far apart) and don't have a difference in charge
(no electronegativity difference). This implies that the Cl-Cl will be the initiation phase of a radical
process.
Show the mechanism of a radical process between X2 and an alkane. - ANSWER: 11009
Show the mechanism of a radical process between X2 and an alkane. - ANSWER: 11009
Show the mechanism of a radical process between X2 and an alkane. - ANSWER: 11009
Show the mechanism of a radical process between X2 and an alkane. - ANSWER: 11009
What do initiation, propagation, and termination consist of? Say what happens at each step using
numbers. - ANSWER: In initiation you start 0 radicals and end with 2 radicals (you use 1 radical to form
2 radicals). In propagation you start with 1 radical and end with 1 radical (you consume 1 radical to
get 1 radical, which generally happens twice so you get 2 different radicals), and in termination you
start with 2 radicals and end with 0 radicals (you use the 2 radicals made by propagation and react
them with themselves). 11009
What do initiation, propagation, and termination consist of? Say what happens at each step using
numbers. - ANSWER: In initiation you start 0 radicals and end with 2 radicals (you use 1 radical to form
2 radicals). In propagation you start with 1 radical and end with 1 radical (you consume 1 radical to
get 1 radical, which generally happens twice so you get 2 different radicals), and in termination you
, start with 2 radicals and end with 0 radicals (you use the 2 radicals made by propagation and react
them with themselves). 11009
Draw the mechanism for the bromination of this alkane, include the reagent(s) and the product(s).
11012 - ANSWER: 11011. Don't use Br· for the propagation step because it's statistically very unlikely
to be floating in the solution compared to Br-Br. You don't need to draw the termination step.
What halides can or cannot go through a radical process? - ANSWER: 11013. Only iodine cannot go
through a radical process because there is an increase in enthalpy (it is endothermic). Also, we don't
use Fluorine because it reacts too much (a huge release of energy)
Which is more reactive: radical chlorine or radical ethane? Why? Draw. - ANSWER: 11014. The radical
chlorine is more reactive because there is a larger drop in potential energy from the radical chlorine
to products (it's higher in potential energy than the radical ethane)
Which is more reactive: radical bromine or radical ethane? Why? Draw. - ANSWER: 11015. The radical
ethane is less stable/more reactive because it is higher in potential energy.
Which is the more reactive radical? Br· or Cl· - ANSWER: Cl· because it is higher in potential energy
than Br· when reacting with an alkane. 11014 and 11015
What does it mean for a radical to be more selective? - ANSWER: It means it breaks only the weakest
C-H bond.
Which reaction proceeds faster, bromination or chlorination, and why? - ANSWER: 11014, 11015.
Chlorination happens faster because it has the lowest activation energy (maximum in energy from the
reactants to one of the transition states), that means the rate determining step is faster.
Which radical halogen, Br• or Cl•, will be more selective? - ANSWER: Br· will be more selective,
meaning that it will break the weakest C-H bond, as it will only react (statistically most likely to react)
with the Hydrogen that requires the least amount of energy to separate, as the amount of energy to
react Br· (the activation energy for Br·) is already enormous.
11016 Which is halogen A: Br2 or Cl2? - ANSWER: Halogen A is Br2, because it's more selective
When you are asked to supply the product/s for a radical bromination.... supply what? - ANSWER:
Only the major product, because it will only react with the H in the weakest C-H bond, which will be
that with the most stable radical carbon, which will be the most stable carbocation
When asked to supply the product/s for a radical chlorination.... supply what? - ANSWER: It is best to
include all possibilities, because they are all relevant, chlorine can react with the H in the really strong
C-H bond.
What does ROOR do? - ANSWER: It helps initiate the radical process in the same way as light.
What are the different ways/reagents and how do you write them to obtain a radical process that
results from light? - ANSWER: Write hv if light is the reagent, write ROOR when ROOR is the reagent.
Both obtain the same products.
11017, what is/are the product(s)? - ANSWER: 11019
11018, what is/are the product(s)? - ANSWER: 11020
Which is the easiest bond to homolytically break? 11021 - ANSWER: The C-H bond at the top carbon
in the cyclohexane, because its resultant carbon radical is secondary with resonance. The far right
carbon would result in primary with resonance.
9781119659594 | All Chapters with Answers and Rationals
What type of bond cleavage must occur to generate radicals? - ANSWER: Homolytic
How must we adjust our curved arrows to account for the formation of radicals? - ANSWER: We need
fishhooks
How many hydrogens at the indicated carbon? Hybridization? In which orbital is the radical? 11001 -
ANSWER: 1, sp^2, p 11002
What's the order of stability of radicals? (By substitution) - ANSWER: 3° > 2° > 1°
Which of the following C-H bonds will be easiest to homolytically cleave? Why? 11003 - ANSWER:
11003. C-Hc. Because it's the weakest (has the lowest potential energy difference from bonded to
not-bonded because the radical is most stable as 3º
Draw the resonance arrows to stabilize the allylic anion. 11004 - ANSWER: 11005
Draw the resonance arrows to stabilize the allylic radical 11006 - ANSWER: 11007
Which of the following C-H bonds will be easiest to homolytically cleave? 11008 - ANSWER: C-Hd
because its resultant radical is most stable - more stable than C-Hc's resultant radical - because it is
secondary with resonance (which is more stable than tertiary without resonance)
What's the most stable radical? (Structurally) - ANSWER: 2º allylic because it is secondary with
resonance.
What are the parts of radical reactions? - ANSWER: 1. Initiation. 2. Propagation. 3. Termination.
If an alkane and Cl2 react, several potential bonds could homolytically break. Which is the easiest
bond to break? What does this implicate. - ANSWER: Cl-Cl. They have the lowest dissociation energy
(243 kJ/mol) maybe because they're somewhat large (far apart) and don't have a difference in charge
(no electronegativity difference). This implies that the Cl-Cl will be the initiation phase of a radical
process.
Show the mechanism of a radical process between X2 and an alkane. - ANSWER: 11009
Show the mechanism of a radical process between X2 and an alkane. - ANSWER: 11009
Show the mechanism of a radical process between X2 and an alkane. - ANSWER: 11009
Show the mechanism of a radical process between X2 and an alkane. - ANSWER: 11009
What do initiation, propagation, and termination consist of? Say what happens at each step using
numbers. - ANSWER: In initiation you start 0 radicals and end with 2 radicals (you use 1 radical to form
2 radicals). In propagation you start with 1 radical and end with 1 radical (you consume 1 radical to
get 1 radical, which generally happens twice so you get 2 different radicals), and in termination you
start with 2 radicals and end with 0 radicals (you use the 2 radicals made by propagation and react
them with themselves). 11009
What do initiation, propagation, and termination consist of? Say what happens at each step using
numbers. - ANSWER: In initiation you start 0 radicals and end with 2 radicals (you use 1 radical to form
2 radicals). In propagation you start with 1 radical and end with 1 radical (you consume 1 radical to
get 1 radical, which generally happens twice so you get 2 different radicals), and in termination you
, start with 2 radicals and end with 0 radicals (you use the 2 radicals made by propagation and react
them with themselves). 11009
Draw the mechanism for the bromination of this alkane, include the reagent(s) and the product(s).
11012 - ANSWER: 11011. Don't use Br· for the propagation step because it's statistically very unlikely
to be floating in the solution compared to Br-Br. You don't need to draw the termination step.
What halides can or cannot go through a radical process? - ANSWER: 11013. Only iodine cannot go
through a radical process because there is an increase in enthalpy (it is endothermic). Also, we don't
use Fluorine because it reacts too much (a huge release of energy)
Which is more reactive: radical chlorine or radical ethane? Why? Draw. - ANSWER: 11014. The radical
chlorine is more reactive because there is a larger drop in potential energy from the radical chlorine
to products (it's higher in potential energy than the radical ethane)
Which is more reactive: radical bromine or radical ethane? Why? Draw. - ANSWER: 11015. The radical
ethane is less stable/more reactive because it is higher in potential energy.
Which is the more reactive radical? Br· or Cl· - ANSWER: Cl· because it is higher in potential energy
than Br· when reacting with an alkane. 11014 and 11015
What does it mean for a radical to be more selective? - ANSWER: It means it breaks only the weakest
C-H bond.
Which reaction proceeds faster, bromination or chlorination, and why? - ANSWER: 11014, 11015.
Chlorination happens faster because it has the lowest activation energy (maximum in energy from the
reactants to one of the transition states), that means the rate determining step is faster.
Which radical halogen, Br• or Cl•, will be more selective? - ANSWER: Br· will be more selective,
meaning that it will break the weakest C-H bond, as it will only react (statistically most likely to react)
with the Hydrogen that requires the least amount of energy to separate, as the amount of energy to
react Br· (the activation energy for Br·) is already enormous.
11016 Which is halogen A: Br2 or Cl2? - ANSWER: Halogen A is Br2, because it's more selective
When you are asked to supply the product/s for a radical bromination.... supply what? - ANSWER:
Only the major product, because it will only react with the H in the weakest C-H bond, which will be
that with the most stable radical carbon, which will be the most stable carbocation
When asked to supply the product/s for a radical chlorination.... supply what? - ANSWER: It is best to
include all possibilities, because they are all relevant, chlorine can react with the H in the really strong
C-H bond.
What does ROOR do? - ANSWER: It helps initiate the radical process in the same way as light.
What are the different ways/reagents and how do you write them to obtain a radical process that
results from light? - ANSWER: Write hv if light is the reagent, write ROOR when ROOR is the reagent.
Both obtain the same products.
11017, what is/are the product(s)? - ANSWER: 11019
11018, what is/are the product(s)? - ANSWER: 11020
Which is the easiest bond to homolytically break? 11021 - ANSWER: The C-H bond at the top carbon
in the cyclohexane, because its resultant carbon radical is secondary with resonance. The far right
carbon would result in primary with resonance.
