Organic Reaction Mechanisms Test Bank Answers Ch.19 Burrows

Chapter 19: Organic Reaction Mechanisms

Test Bank

Type: multiple choice question

Title: Chapter 19 Question 01

1) From the following molecules, pick out the one which is the strongest nucleophile:

a. A

Feedback: A nucleophile is a reagent that reacts with an electrophile to form a covalent bond by donating its pair of non-bonding electrons. This nucleophile must have a pair of electrons to donate, and this electrophile must have an empty orbital to accept them.

Section reference: 19.1

b. B

Feedback: A nucleophile is a reagent that reacts with an electrophile to form a covalent bond by donating its pair of non-bonding electrons. This nucleophile must have a pair of electrons to donate, and this electrophile must have an empty orbital to accept them.

Section reference: 19.1

c. C

Feedback: A nucleophile is a reagent that reacts with an electrophile to form a covalent bond by donating its pair of non-bonding electrons. This nucleophile must have a pair of electrons to donate, and this electrophile must have an empty orbital to accept them.

Section reference: 19.1

d. D

Feedback: A nucleophile is a reagent that reacts with an electrophile to form a covalent bond by donating its pair of non-bonding electrons. This nucleophile must have a pair of electrons to donate, and this electrophile must have an empty orbital to accept them.

Section reference: 19.1

Type: multiple choice question

Title: Chapter 19 Question 02

2) Which of the following shows resonance?

a. A

Feedback: Resonance, like conjugation, involves the internal movement of non-bonded and pi-electrons within a molecule. It does not involve the movement of sigma-electrons nor the movement of electrons between molecules, as these processes are technically reactions.

Section reference: 19.1

b. B

Feedback: Resonance, like conjugation, involves the internal movement of non-bonded and pi-electrons within a molecule. It does not involve the movement of sigma-electrons nor the movement of electrons between molecules, as these processes are technically reactions.

Section reference: 19.1

c. C

Feedback: Resonance, like conjugation, involves the internal movement of non-bonded and pi-electrons within a molecule. It does not involve the movement of sigma-electrons nor the movement of electrons between molecules, as these processes are technically reactions.

Section reference: 19.1

d. D

Feedback: Resonance, like conjugation, involves the internal movement of non-bonded and pi-electrons within a molecule. It does not involve the movement of sigma-electrons nor the movement of electrons between molecules, as these processes are technically reactions.

Section reference: 19.1

Type: multiple response question

Title: Chapter 19 Question 03

3) Which of the following molecules contain conjugation? Please select all that apply.

a. A

Feedback: Conjugation, like resonance, involves the internal movement of non-bonded and pi-electrons within a molecule. The traditional mnemonic for conjugation is a planar molecule with alternating double-single-double bonds.

Section reference: 19.1

b. B

Feedback: Conjugation, like resonance, involves the internal movement of non-bonded and pi-electrons within a molecule. The traditional mnemonic for conjugation is a planar molecule with alternating double-single-double bonds.

Section reference: 19.1

c. C

Feedback: Conjugation, like resonance, involves the internal movement of non-bonded and pi-electrons within a molecule. The traditional mnemonic for conjugation is a planar molecule with alternating double-single-double bonds.

Section reference: 19.1

d. D

Feedback: Conjugation, like resonance, involves the internal movement of non-bonded and pi-electrons within a molecule. The traditional mnemonic for conjugation is a planar molecule with alternating double-single-double bonds.

Section reference: 19.1

Type: multiple response question

Title: Chapter 19 Question 04

4) Which of the following molecules exhibit conjugation? Please select all that apply.

a. A

Feedback: Conjugation, like resonance, involves the internal movement of non-bonded and pi-electrons within a molecule. The traditional mnemonic for conjugation is a planar molecule with alternating double-single-double bonds.

Section reference: 19.1

b. B

Feedback: Conjugation, like resonance, involves the internal movement of non-bonded and pi-electrons within a molecule. The traditional mnemonic for conjugation is a planar molecule with alternating double-single-double bonds.

Section reference: 19.1

c. C

Feedback: Conjugation, like resonance, involves the internal movement of non-bonded and pi-electrons within a molecule. The traditional mnemonic for conjugation is a planar molecule with alternating double-single-double bonds.

Section reference: 19.1

d. D

Feedback: Conjugation, like resonance, involves the internal movement of non-bonded and pi-electrons within a molecule. The traditional mnemonic for conjugation is a planar molecule with alternating double-single-double bonds.

Section reference: 19.1

Type: multiple response question

Title: Chapter 19 Question 05

5) Which of the following structures do not contribute to the resonance hybrid of a benzyl cation? Please select all that apply.

a. A

Feedback: Resonance, like conjugation, involves the internal movement of non-bonded and pi-electrons within a molecule. It does not involve the movement of sigma-electrons nor the movement of electrons between molecules, as these processes are technically reactions.

Section reference: 19.1

b. B

Feedback: Resonance, like conjugation, involves the internal movement of non-bonded and pi-electrons within a molecule. It does not involve the movement of sigma-electrons nor the movement of electrons between molecules, as these processes are technically reactions.

Section reference: 19.1

c. C

Feedback: Resonance, like conjugation, involves the internal movement of non-bonded and pi-electrons within a molecule. It does not involve the movement of sigma-electrons nor the movement of electrons between molecules, as these processes are technically reactions.

Section reference: 19.1

d. D

Feedback: Resonance, like conjugation, involves the internal movement of non-bonded and pi-electrons within a molecule. It does not involve the movement of sigma-electrons nor the movement of electrons between molecules, as these processes are technically reactions.

Section reference: 19.1

Type: multiple choice question

Title: Chapter 19 Question 06

6) From the following carbocations, pick out the most stable:

a. A

Feedback: Carbocations are electron deficient species with a positively charged carbon atom. Generally, the carbon atom is sp² hybridized with the remaining p orbital being empty. Carbocations can be stabilised inductively and mesomerically using electron-donating groups. As a rule of thumb, the more substituted a carbocation is, the more stable it is.

Section reference: 19.1

b. B

Feedback: Carbocations are electron deficient species with a positively charged carbon atom. Generally, the carbon atom is sp² hybridized with the remaining p orbital being empty. Carbocations can be stabilised inductively and mesomerically using electron-donating groups. As a rule of thumb, the more substituted a carbocation is, the more stable it is.

Section reference: 19.1

c. C

Feedback: Carbocations are electron deficient species with a positively charged carbon atom. Generally, the carbon atom is sp² hybridized with the remaining p orbital being empty. Carbocations can be stabilised inductively and mesomerically using electron-donating groups. As a rule of thumb, the more substituted a carbocation is, the more stable it is.

Section reference: 19.1

d. D

Feedback: Carbocations are electron deficient species with a positively charged carbon atom. Generally, the carbon atom is sp² hybridized with the remaining p orbital being empty. Carbocations can be stabilised inductively and mesomerically using electron-donating groups. As a rule of thumb, the more substituted a carbocation is, the more stable it is.

Section reference: 19.1

e. E

Feedback: Carbocations are electron deficient species with a positively charged carbon atom. Generally, the carbon atom is sp² hybridized with the remaining p orbital being empty. Carbocations can be stabilised inductively and mesomerically using electron-donating groups. As a rule of thumb, the more substituted a carbocation is, the more stable it is.

Section reference: 19.1

Type: matching question

Title: Chapter 19 Question 07

7) Match the following acids to their acidity constant, K_a (in water):

Feedback:

Section reference: 19.2

a. K_a = 10^-5 = D

b. K_a = 10^-7 = A

c. K_a = 10^-16 = C

d. K_a = 10^-50 = B

Type: multiple choice question

Title: Chapter 19 Question 08

8) Using the pK_a data provided, pick out the acid that is most dissociated in water.

a. Acid A; pK_a = ‑9

Feedback: An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Conversely, the smaller the pK_a, the stronger the acid.

Section reference: 19.2

b. Acid B; pK_a = 0

Feedback: An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Conversely, the smaller the pK_a, the stronger the acid.

Section reference: 19.2

c. Acid C; pK_a = +2

Feedback: An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Conversely, the smaller the pK_a, the stronger the acid.

Section reference: 19.2

d. Acid D; pK_a = +50

Feedback: An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Conversely, the smaller the pK_a, the stronger the acid.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 09

9) Which of the following phenols has the largest acidity constant, K_a?

a. A

Feedback: An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Phenols are generally more acidic than alcohols and less acidic than carboxylic acids.

Section reference: 19.2

b. B

Feedback: An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Phenols are generally more acidic than alcohols and less acidic than carboxylic acids.

Section reference: 19.2

c. C

Feedback: An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Phenols are generally more acidic than alcohols and less acidic than carboxylic acids.

Section reference: 19.2

d. D

Feedback: An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Phenols are generally more acidic than alcohols and less acidic than carboxylic acids.

Section reference: 19.2

e. E

Feedback: Correct. An acidity constant is a thermodynamic measure of acidity. The larger the value of K_a, the stronger the acid. Phenols are generally more acidic than alcohols and less acidic than carboxylic acids.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 10

10) Toluene can be deprotonated using n-BuLi in THF; pick out its conjugate base:

a. A

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. In order to consider this stability, you will need to look at inductive and resonance stabilisation for each conjugate base.

Section reference: 19.2

b. B

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. In order to consider this stability, you will need to look at inductive and resonance stabilisation for each conjugate base.

Section reference: 19.2

c. C

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. In order to consider this stability, you will need to look at inductive and resonance stabilisation for each conjugate base.

Section reference: 19.2

d. D

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. In order to consider this stability, you will need to look at inductive and resonance stabilisation for each conjugate base.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 11

11) From the following molecules, pick out the strongest base:

a. A

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

b. B

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

c. C

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

d. D

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 12

12) From the following molecules, pick out the strongest acid:

a. A

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. In order to consider this stability, you will need to look at inductive and resonance stabilisation for each conjugate base.

Section reference: 19.2

b. B

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. In order to consider this stability, you will need to look at inductive and resonance stabilisation for each conjugate base.

Section reference: 19.2

c. C

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. In order to consider this stability, you will need to look at inductive and resonance stabilisation for each conjugate base.

Section reference: 19.2

d. D

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. In order to consider this stability, you will need to look at inductive and resonance stabilisation for each conjugate base.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 13

13) From the following molecules, pick out the strongest base:

a. A

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

b. B

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

c. C

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

d. D

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

e. E

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 14

14) From the following molecules, pick out the weakest base:

a. A

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

b. B

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

c. C

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

d. D

Feedback: Correct. As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

e. E

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid. Also, the weaker the base, the stronger the conjugate acid.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 15

15) From the following carbocations, pick out the most acidic:

a. A

Feedback: Correct. As a rule of thumb, the more stable the conjugate base, the stronger the acid.

Section reference: 19.2

b. B

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid.

Section reference: 19.2

c. C

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid.

Section reference: 19.2

d. D

Feedback: As a rule of thumb, the more stable the conjugate base, the stronger the acid.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 16

16) For the following reaction, deduce whether it involves oxidation, reduction or neither:

a. Oxidation

Feedback: In order to deduce whether this process involves oxidation or reduction, the relative oxidation levels of the product and the starting material must be considered.

Section reference: 19.2

b. Reduction

Feedback: In order to deduce whether this process involves oxidation or reduction, the relative oxidation levels of the product and the starting material must be considered.

Section reference: 19.2

c. Neither

Feedback: In order to deduce whether this process involves oxidation or reduction, the relative oxidation levels of the product and the starting material must be considered.

Section reference: 19.2

Type: multiple choice question

Title: Chapter 19 Question 17

17) Pick out the term which describes the following reaction:

a. Radical elimination

Feedback: Bromination of an alkene is is an addition process as two reagents (alkene and Br₂) are required to form a single product.

Section reference: 19.2

b. Nucleophilic substitution

Feedback: Bromination of an alkene is an addition process as two reagents (alkene and Br₂) are required to form a single product.

Section reference: 19.2

c. Electrophilic addition

Feedback: Bromination of an alkene is an addition process as two reagents (alkene and Br₂) are required to form a single product.

Section reference: Section 19.2

Type: multiple choice question

Title: Chapter 19 Question 18

18) Pick out the term which describes the following reaction:

a. Chemoselectivity

Feedback: Addition of an unsymmetrical molecule, like HCl, to an unsymmetrical alkene, such as cyclohexa-1,3-diene, can give two different chlorocyclohexene products.

Section reference: 19.3

b. Stereoselectivity

Feedback: Addition of an unsymmetrical molecule, like HCl, to an unsymmetrical alkene, such as cyclohexa-1,3-diene, can give two different chlorocyclohexene products.

Section reference: 19.3

c. Regioselectivity

Feedback: Addition of an unsymmetrical molecule, like HCl, to an unsymmetrical alkene, such as cyclohexa-1,3-diene, can give two different chlorocyclohexene products.

Section reference: 19.3

Type: multiple response question

Title: Chapter 19 Question 19

19) Pick out the terms which describe the following reaction. Please select all that apply.

a. Chemoselectivity

Feedback: Reduction of the ketone with sodium borohydride gives the corresponding secondary alcohol.

Section reference: 19.3

b. Regioselectivity

Feedback: Reduction of the ketone with sodium borohydride gives the corresponding secondary alcohol.

Section reference: 19.3

c. Stereoselectivity

Feedback: Reduction of the ketone with sodium borohydride gives the corresponding secondary alcohol.

Section reference: 19.3

Type: multiple response question

Title: Chapter 19 Question 20

20) Pick out the terms which describe the following reaction. Please select all that apply.

a. Chemoselectivity

Feedback: Reduction of the alkyne with hydrogen, Pd and Lindlar’s catalyst gives the corresponding alkene.

Section reference: 19.3

b. Regioselectivity

Feedback: Reduction of the alkyne with hydrogen, Pd and Lindlar’s catalyst gives the corresponding alkene.

Section reference: 19.3

c. Stereoselectivity

Feedback: Reduction of the alkyne with hydrogen, Pd and Lindlar’s catalyst gives the corresponding alkene.

Section reference: 19.3

Type: true-false

Title: Chapter 19- Question 21

21) In general, the more stable the carbanion or carbocation, the higher the equilibrium constant (K) and the greater the concentration of the product carbanion or carbocation at equilibrium.

a. True

Feedback: In general, the more stable the carbanion or carbocation, the higher the equilibrium constant (K) and the greater the concentration of the product carbanion or carbocation at equilibrium.

Section reference: 19.1

b. False

Feedback: Type feedback here (maximum of 1000 characters (including spaces))

Section reference: 19.1

Type: multiple response question

Title: Chapter 19 Question 22

22) Select those from A-D that are electron donating groups through mesomeric effects (also known as resonance effects).

Feedback: Whereas inductive effects involve the movement electrons through the sigma bonds, mesomeric effects involve the delocalization of electron density through pi bonds. Groups and atoms can be classified as having a negative mesomeric effect (−M) or a positive mesomeric effect (+M). Like inductive effects, mesomeric effects can lead to stabilization of carbocations, carbanions, and radicals by delocalization.

Section reference: 19.1

a. A

b. B

c. C

d. D

Type: multiple response question

Title: Chapter 19 Question 23

23) Select molecules below that have conjugated double bonds (select all correct answers)

Feedback: Mesomeric effects can be effective longer distances than inductive effects, provided that the molecules are conjugated. Conjugated systems have alternate single and double bonds which are appropriately positioned for the movement of pairs of electrons.

Section reference: 19.1

a. B

b. C

c. D

d. A

Type: multiple choice question

Title: Chapter 19 Question 24

24) An electronegative atom (e.g. F) bonded to a carbon chain causes a polarization of the C–C bonds. The notation “– I” is often used to represent this, but to what does this refer?

a. negative inductive effect

Feedback: The polarization of the C−C bonds caused by the C−F bond is called a negative inductive effect and the chlorine atom is referred to as a −I group. It is called a −I group because it draws electrons away from the carbon chain.

Section reference: 19.1

b. positive induction effect

Feedback: Positive induction effect is the donation of electrons through sigma bonds and is symbolised by +I. Few groups are classified as +I, with alkyl groups being an important +I group. Considering this example has an electronegative atom, it is not positive inductive effect.

Section reference: 19.1

c. hyperconjugation

Feedback: Hyperconjugation describes the donation of electrons from nearby C−H or C−C σ bonds, This example discusses the term for the electronegative group.

Section reference: 19.1

d. resonance

Feedback: Stabilization of neutral molecules or ions by delocalization of bonding or non-bonding electrons is called resonance. Considering this example is discussing polarisation through sigma bonds, resonance is not important here.

Section reference: 19.1

Type: true-false

Title: Chapter 19 Question 25

25) The symmetrical cleavage of a covalent bond is called heterolytic cleavage.

a. True

Feedback: The symmetrical cleavage of a covalent bond is called homolytic cleavage (homolysis). As the bond breaks in homolytic cleavage both atoms in the bond will receive one electron from the bond each. Each atom from the bond now contains an unpaired electron and is therefore a radical.

Section reference: 19.1

b. False

Feedback: The symmetrical cleavage of a covalent bond is called homolytic cleavage (homolysis). As the bond breaks in homolytic cleavage both atoms in the bond will receive one electron from the bond each. Each atom from the bond now contains an unpaired electron and is therefore a radical.

Section reference: 19.1