Which of the following statements correctly describe the conventions used when writing equations for
organic reactions? Select all that apply.
The symbol Δ is used to indicate heat.
Formulas for inorganic by-products of a reaction are often omitted.
Reagents are often shown above the reaction arrow.
Organic molecules only undergo reactions that are unique to organic substances.
False. Organic molecules, like other compounds, can undergo acid-base and redox reactions in addition
to reactions that are typical of organic substances only.
A reaction in which an atom or group of atoms is replaced by another atom or group or atoms is
addition
classified as a(n) reaction.
Substitution
In a(n), _ reaction, elements of the starting material are "lost" and a new bond_ is formed
Elimination
Pi
A reaction in which elements are added to a starting material is classified as a(n) _____ reaction. For this
type of reaction to occur, the starting material must have a _____ bond to which elements can be
added.
addition, π
Which of the following options correctly interpret the equation shown? Select all that apply.
Reaction of the starting material with BH3 occurs before H2O2 is added to the reaction mixture.
The product shows no boron atoms because this element is part of an inorganic by-product.
This reaction involves two sequential steps.
Which of the following are types of organic reactions? Select all that apply.
Addition
Elimination
Substitution
Which of the following options correctly describe the general characteristics of a substitution reaction?
Select all that apply.
Heteroatoms such as oxygen or a halogen are often involved in substitution reactions.
A bond breaks and a new bond is formed at the same carbon atom in this type of reaction.
Which of the following options correctly describe the characteristics of an elimination reaction? Select
all that apply.
Two atoms or groups are eliminated, usually from adjacent atoms in the compound.
Hydrogen is often one of the atoms eliminated in this reaction type.
In an elimination reaction, two σ bonds are broken and one π bond is formed.
Select all the statements that correctly describe the changes occurring in addition reactions.
A π bond is broken in an addition reaction.
Compounds with double bonds can undergo addition reactions.
A detailed description of the steps in a reaction, including information on the relative order and
rate of bond formation and cleavage, is called a reaction _____
Mechanism
Heterolytic bond cleavage _____. (Select all the options that complete the sentence correctly.)
results in uneven division of the electrons from the bond
is a process that requires energy
is typical of a bond between two atoms that have different electronegativities
Which of the following options correctly describe an action mechanism? Select all that apply.
A reaction mechanism will include the structures of any reaction intermediates formed in a multistep
process.
A mechanism shows the relative order in which bonds are broken and formed.
A reaction mechanism gives a detailed description of bonds broken and formed in a reaction.
A half-headed (fishhook) curved arrow is used to show the movement of a ______ electron(s),
whereas a full-headed arrow shows the movement of a ______ electron(s).
single, pair of
If a bond C-Z undergoes heterolytic cleavage and both bonding electrons move to the carbon
atom, the intermediate formed will have a ______ charge on the carbon atom and will be called a
______
negative, carbanion
Which of the following shows the correct use of curved arrows to represent the homolytic
cleavage of a C-C bond?
Scheme 3
Match each type of bond cleavage to the correct description.
Heterolytic bond cleavage - Both bonding electrons go to the same atom.
Homolytic bond cleavage - Electrons are evenly divided between bonding atoms.
Which of the following options correctly describe the use of different types of arrows to show
electron movement? Select all that apply
A curved arrow with a full head shows the movement of a pair of electrons.
A half-headed curved arrow is also called a fishhook arrow.
The movement of a single electron is shown by a half-headed curved arrow.
Match each reaction intermediate to the correct description of its structure.
Carbocation - Incomplete octet, positive charge on C
Carbanion - Full octet, lone pair and negative charge on C
Radical - Incomplete octet, unpaired electron
Match each type of heterolytic bond cleavage to the intermediates produced. Assume that the
bond cleaved is a C-Z bond where Z is a heteroatom
A carbocation is formed – if both bonding electrons move to atom Z.
A carbanion is formed - if both bonding electrons move to the carbon atom.
If both bonding electrons move to atom Z - the previously bonded carbon atom will have a positive
charge.
If both bonding electrons move to the carbon atom - the previously bonded carbon atom will have a
negative charge.
Which of the following schemes shows the correct use of curved arrows to represent the
heterolytic cleavage of a C-O bond?
Scheme 3
Heterolytic bond cleavage _____
is typical of a bond between two atoms that have different electronegativities
is a process that requires energy
results in uneven division of the electrons from the bond
Describe the two types of heterolytic cleavage of a C-Z bond according to the two options
shown.
A reaction intermediate that has a lone pair and a negative charge on a carbon atom is called
a(n) ______, whereas an intermediate with a positive charge on a carbon atom is called a(n) ______.
carbanion, carbocation
Match each type of bond formation with the correct description.
Which of the following options correctly describe the use of the arrows shown? Select
all that apply.
Arrow c shows the movement of a single electron.
Arrow a shows the direction of electron movement of a pair of electrons.
Arrow e is a reaction arrow.
Which of the following shows the correct curved arrow mechanism for the overall process?
Which of the following options correctly describe ΔHo for a reaction? Select all that apply.
ΔHo is also called the heat of reaction.
If ΔHo is positive, the reaction absorbs heat energy from its surroundings.
If ΔHo is negative, the reaction is exothermic.
Match each type of bond cleavage to the structure of the reaction intermediate that results.
The bond dissociation energy is the energy needed to _____ cleave a(n) _____ bond.
homolytically, covalent
Which of the following options correctly describe bond formation? Select all that apply.
When two radicals bond, each donates one bonding electron.
Bond formation always releases energy
Match each arrow type to the correct description of its function.
Match each process correctly to the energy change and sign of ΔHo.
Which of the following shows the correct curved arrow mechanism for the overall process?
The energy required to homolytically cleave a covalent bond is called the bond _____ energy.
Dissociation
Match the sign of ΔHo for a reaction with the information this gives about the overall energy
change.
Match each type of bond formation with the correct description.
The bond dissociation energy for the H-F bond is 569 kJ/mol. Which of the following options
correctly interpret this information? Select all that apply
569 kJ of heat will be absorbed in order to break 1 mole of H-F bonds.
569 kJ of heat will be released in the formation of 1 mole of H-F bonds.
The stronger the bond, the _____ the amount of energy needed to break it, i.e., the _____ the
bond dissociation energy.
greater, higher
Place the following bonds in order of increasing bond dissociation energy, starting with the bond
that has the smallest dissociation energy at the top of the list
If ΔHo for a particular reaction is positive, select all the statements that correctly describe the
reaction.
The reaction is endothermic.
More energy is needed to break bonds than is released by forming bonds.
There is a net increase in the enthalpy of the system.
What information can thermodynamic data provide? Select all that apply.
Favored direction for a particular reaction
Relative energies of reactants and products
Relative amounts of reactants and products at equilibrium
Which of the following options correctly describe bond strength, bond dissociation energy, and
their periodic trends? Select all that apply.
Bond dissociation energy increases from left to right across a period, when comparing the same type of
bond.
As bond strength increases, bond dissociation energy increases.
Bond strength and bond dissociation energy both decrease as the size of the bonded atoms increase.
The C-O bond in CH3OH has a _____ bond dissociation energy than the C-S bond in CH3SH
because C-O bond is _____ and _____.
higher, shorter, stronger
If ΔHo for a reaction is negative, the reaction is _____. The energy released in forming bonds is
_____ than the energy needed to break bonds, and the bonds formed in the product(s) are _____ than
the bonds broken in the starting material(s).
exothermic, greater, stronger
Match the value of Keq with the direction favored for a specific reaction at equilibrium.
Match each type of data with the information provided about a particular reaction.
If ΔHo for a particular reaction is positive, select all the statements that correctly describe the
reaction.
The reaction is endothermic.
There is a net increase in the enthalpy of the system.
More energy is needed to break bonds than is released by forming bonds.
Which of the following options correctly describe Keq, the equilibrium constant for a reaction?
Select all that apply.
Keq provides information about the relative amounts of starting materials and products at equilibrium.
If Keq is close to 1, there will be appreciable amounts of both reactants and products present at
equilibrium.
If Keq is much greater than 1, the products are favored at equilibrium.
Which of the following options correctly describe ΔGo, the Gibbs free energy change, for a
reaction? Select all that apply.
ΔGo is a measure of the relative stabilities of the reactants and products.
ΔGo is a measure of the relative energies of the reactants and products.
ΔGo is negative for a reaction that proceeds in the direction written.
Match each combination of ΔGo and Keq with the preferred direction of reaction at equilibrium.
A reaction will favor the products as written if the stability of the product(s) is _____ than the
stability of the reactant(s). This will be the case if the free energy of the product(s) is _____ than the free
energy of the reactant(s). Such a reaction also has a value for Keq that is much _____ than 1.
greater, lower, larger
The overall energy difference between reactants and products is called the Gibbs _ energy
change of a reaction and is symbolized by ΔGo. The value of ΔGo is _ for a reaction that proceeds
spontaneously in the direction written.
Blank 1: free
Blank 2: negative or less than zero
A reaction that favors the reactants at equilibrium will have a _____ value for ΔGo and a value
of Keq that is _____ than 1.
positive, less
A reaction has an equilibrium constant Keq of 2.5 x 10-2 at 298 K. ΔGo for this reaction is equal
to _____.
ΔGo = -2.303RT log Keq = -2.303 x 8.314 x 298 x log (2.5 x 10-2)
= 9140 J/mol = +9.14 kJ/mol
Monosubstituted cyclohexanes exist as an equilibrium mixture of two chair conformations, as
shown. The values of Keq for some cyclohexane derivatives are provided. Select all the statements that
correctly reflect this data.
The change from equatorial to axial conformation becomes less favorable as the R substituent increases
in size.
The ΔGo value for the conformational change from axial to equatorial when R = C(CH3)3 is
approximately -21 kJ/mol.
When R = CH3, both axial and equatorial conformations occur at equilibrium.
Which of the following options correctly describe the preferred direction of any reaction? Select
all that apply.
A reaction that favors the products as written will have a negative value for ΔGo and Keq > 1.
A reaction will proceed toward compounds with increased stability.
Equilibrium favors products that are lower in free energy than the starting materials.
Which of the following options correctly describe the entropy of a system? Select all that apply.
Entropy is related to freedom of movement.
Entropy can be viewed as a measure of randomness or disorder.
Reactions resulting in an increase in entropy are favored.
Match each value of ΔGo to the approximate value of Keq in each case.
Cis-1-methyl-4-phenylcyclohexane exists as a equilibrium mixture of two chair conformations, as shown.
ΔGo for the conformational change as written is equal to +4.73 kJ/mol. Select all the statements that
correctly interpret this data.
Conformer A is more stable than conformer B.
Conformer B is higher in energy than conformer A.
The value of Keq for this conformational change (A to B) is < 1.
The free energy change (ΔGo) for a reaction is related to the _ or heat of reaction (ΔHo), the
change in _ (ΔSo), and the _ at which the reaction occurs.
Blank 1: enthalpy or enthalpy change
Blank 2: entropy, disorder, order, or randomness
Blank 3: temperature
A measure of the randomness or disorder in a system is called the _____ of the system.
Reactions resulting in a(n) _____ in disorder are favored.
entropy, increase
Which of the following changes generally result in an increase in entropy? Select all that apply.
The opening of a ring to give an acyclic compound.
Decomposition of a single compound to form two or more products.
In general, reactions are favored if the enthalpy of the system _____ and the entropy of the
system _____. The combined effects of enthalpy and entropy changes determine the free energy of the
system.
decreases, increases
Which of the following reactions involve an increase in entropy? Select all that apply.
For an organic reaction where the entropy change is considered to be small, a reaction that has
a positive value for ΔHo favors the _____ at equilibrium. In such a reaction, the bonds in the products
are _____ than the bonds in the starting materials.
reactants, weaker
Match the description of each reaction with the corresponding change in entropy.
In a particular organic reaction, two compounds react to give two products. ΔHo for the reaction
is equal to -15 kJ/mol. Which of the following options correctly describe this process, assuming that the
temperature is fairly low? Select all that apply.
The reaction favors the products at equilibrium.
The bonds formed in the products are stronger than the bonds in the starting materials.
The entropy change in the reaction will probably have little effect on the free energy change.
The reaction shown probably involves a(n) _____ in entropy because the product has _____
freedom of movement than the reactant.
decrease, less
Which of the following options correctly describe an energy diagram for a one-step reaction?
Select all that apply.
Energy is plotted on the y axis.
The energy maximum on the diagram represents the transition state of the reaction.
An organic reaction has a ΔHo equal to +35 kJ/mol. If the entropy change is assumed to be small,
this reaction favors the _____ and has an equilibrium constant _____ than 1.
reactants, less
The energy diagram for a single-step reaction is shown. Match each point on the graph to the
correct designation.
Every chemical reaction proceeds through a high-energy unstable species as reactants are
converted to products. This unstable energy maximum is called the _ state, and the energy required to
form this species from the reactants is called the _ energy for the reaction.
Blank 1: transition
Blank 2: activation
A reaction with a high-energy transition state has _____ activation energy and occurs at a _____
rate than a reaction with a low-energy transition state.
high, slower
Select the structure that best represents the transition state for the given overall reaction.
Which of the following options correctly describe an organic reaction for which the change in
entropy is assumed to be small? Select all that apply.
If a reaction has ΔHo < 0, the energy of the products is lower than the energy of the reactants.
The product is favored if ΔHo < 0.
The two energy diagrams represent two different reaction pathways. Select all the statements
that correctly interpret this data.
The first reaction has a lower activation energy than the second.
Both reactions are exothermic.
Which of the following options correctly describe the transition state of a reaction?
Select all that apply.
A transition state is an unstable energy maximum formed as reactants are converted to products.
The transition state contains bonds that are partially broken and/or formed.
If a reaction has a high activation energy (Ea), it implies that _____. (Select all that apply.)
a large amount of energy is needed to break bonds in the reaction
the reaction will be slower than a reaction with a lower activation energy
Select the structure that best represents the transition state for the given overall reaction.
Many organic reactions involve more than a single step. A reactive species that is formed in one
step and used up in the next is called a reactive _. Such a reactive species can sometimes be isolated,
even though it may be short-lived, unlike the state, which is the unstable energy maximum for each
step.
Blank 1: intermediate
Blank 2: transition
Which of the following options correctly describe the energy diagram for a multistep process?
Select all that apply. (Assume that the energy diagram plots enthalpy versus reaction coordinate and not
free energy.)
The peaks in the diagram will usually be of different heights.
This energy diagram will have several peaks, each representing a transition state.
The difference in energy between the products and reactants is equal to ΔH for the reaction.
Compound A can be converted into two different products, B and C. The energy diagram for
these one-step processes is provided. Select all the statements that interpret this data correctly.
The conversion A → C is an exothermic reaction.
The reaction A → C occurs faster than the reaction A → B.
ΔHo for the reaction A → B is a positive value.
Every chemical reaction proceeds through a high-energy unstable species as reactants are
converted to products. This unstable energy maximum is called the state, and the energy required to
form this species from the reactants is called the energy for the reaction.
Blank 1: transition
Blank 2: activation
Which of the following options correctly describe the reactive intermediate(s) of a reaction?
Select all that apply.
A reactive intermediate is formed in one step and used up in the next.
A transition state is formed before each reactive intermediate in a reaction.
A reactive intermediate is always at a lower energy than the transition state leading to its
formation.
Match each marked point on the accompanying energy diagram with its correct meaning.
Which of the following options correctly describe the effects of different variables on the rate of
a reaction? Select all that apply.
A reaction proceeds faster if the concentrations of the reacting species are increased.
A reaction generally proceeds faster at a higher temperature.
Which of the following options correctly describe the rate equation of a reaction? Select all that
apply.
The rate law is related to the mechanism of the reaction.
The rate equation for a reaction is determined experimentally.
The rate equation reflects the concentrations of reactants that are involved in the rate-
determining step.
Which of the following options correctly describe the energy diagram for a multistep process?
Select all that apply. (Assume that the energy diagram plots enthalpy versus reaction coordinate and not
free energy.)
The peaks in the diagram will usually be of different heights.
This energy diagram will have several peaks, each representing a transition state.
The difference in energy between the products and reactants is equal to ΔH for the reaction.
Which of the following factors have no effect on the rate of a reaction? Select all that apply.
ΔHo, ΔGo, Keq
A rate law or rate equation expresses the relationship between the _____ of a reaction and the
_____ of the reactants.
rate, concentration
Which of the following factors affect the value of k, the rate constant for a reaction? Select all
that apply.
Temperature
Activation energy
A particular reaction is found to be bimolecular. This means that _____.
two reactants are involved in the rate-determining step
The sum of the exponents of the concentration terms in the rate equation is called the _ of the
reaction. A reaction that has the rate law rate = k[A][B] follows _ kinetics overall.
Blank 1: order
Blank 2: second or 2nd
Blank 3: order
In a multistep reaction, the step with the _____ rate affects the overall reaction rate most. The
rate equation for the reaction will therefore reflect the concentrations of the reactants involved in this
step only, which is called the rate-_____ step of the reaction.
slowest, determining
A fast reaction will have a _____ rate constant k and a _____ activation energy Ea.
large, low
A reaction involving only one reactant is said to be _, while a reaction involving two reactants in
the rate-determining step is described as _
Blank 1: unimolecular
Blank 2: bimolecular
The rate law for a particular reaction is determined experimentally to be rate = k[A]2[B]. The
reaction is _____ order with respect to reactant A but follows _____-order kinetics overall.
second, third
Which rate law is consistent with the reaction mechanism shown?
Rate = k[CH3CH2Br][CH3O–]
The rate equation for the reaction between the alkyl halide (CH3)2CHBr and the hydroxide anion
–
OH is given by the expression rate = k[(CH3)2CHBr]. Why does this rate equation not include the
concentration of the –OH anion?
The rate-determining step involves only the compound (CH3)2CHBr.
A substance that increases the rate of reaction without being used up in the reaction is called
a(n) _. Such a substance acts by _ the activation energy of the reaction so that a greater proportion of
the molecules have sufficient energy to react.
Blank 1: catalyst
Blank 2: decreasing, lowering, or reducing
The substrate of an enzyme-catalyzed reaction binds to the enzyme's _ site. The enzyme speeds
up the rate of the reaction by _ the activation energy.
Blank 1: active
Blank 2: lowering or decreasing
Which rate law is consistent with the reaction mechanism shown?
Rate = k[(CH3)3CBr]
Which of the following options correctly describe a catalyst for a particular reaction? Select all
that apply.
A catalyst increases the rate of a reaction.
A catalyst may be used up in one step and regenerated in another.
A catalyst lowers the activation energy for a reaction.
Which of the following options correctly describe an enzyme? Select all that apply.
An enzyme lowers the activation energy for a given reaction.
The region of the enzyme to which the substrate binds is called the active site.
