Deck 15: Ð Bond Electrophiles Connected to Leaving Groups

Question 1

What is the best leaving group in an S_NAr reaction?

A)fluoride
B)chloride
C)bromide
D)iodide

Answer 1

fluoride

Question 2

Which carboxylic acid derivative would you expect to be most reactive to a nucleophilic acyl substitution reaction?

A)
B)
C)
D)

Answer 2

Question 3

Which of the following best describes cyanate groups in S_NAr reactions?

A)electron withdrawing and activating
B)electron withdrawing and deactivating
C)electron donating and activating
D)electron donating and deactivating

Answer 3

electron withdrawing and activating

Question 4

Which of the following best describes the role of acid in acyl substitution reactions?

A)It activates electrophiles.
B)It activates electrophiles and nucleophiles.
C)It improves leaving group capability.
D)It activates electrophiles and improves leaving group capability.

Question 5

Which of the following best describes DIBAL in the reaction scheme shown below?

A)nucleophilic and oxidizing
B)nucleophilic and reducing
C)electrophilic and oxidizing
D)electrophilic and reducing

Question 6

How many equivalents of a Grignard reagent will an ester react with?

A)0
B)1
C)2
D)3

Question 7

Which of the following best describes the conditions required to reduce an acid anhydride?

A)LiAlH₄ will accomplish this transformation.
B)NaBH₄ will accomplish this transformation.
C)NaCNBH₃ will accomplish this transformation.
D)Both LiAlH₄ and NaBH₄ will accomplish this transformation.

Question 8

Which of the following reagents can reduce an ester?

A)LiAlH₄
B)NaBH₄
C)NaCNBH₃
D)H₂O

Question 9

What acts as the nucleophile in the first step of the following reaction?

A)hydride
B)lithium
C)aluminum
D)ethyl benzoate

Question 10

Which of the following best describes the role of base in acyl substitution reactions?

A)It activates electrophiles.
B)It activates nucleophiles.
C)It improves leaving group capability.
D)It activates electrophiles and improves leaving group capability.

Question 11

How many hydrides from LiAlH₄ are required to reduce a carboxylic acid?

A)0
B)1
C)2
D)3

Question 12

Why is base added in excess when reacting an acid chloride with an amine?

A)to deprotonate the acid chloride and make it more nucleophilic
B)to deprotonate the amine and make it more nucleophilic
C)to form a salt with the formed HCl byproduct
D)to hydrogen bond with the amine and acid chloride to bring them together

Question 13

When forming an amide from an acid chloride,how many equivalents of amine are required if no base is used?

A)0
B)1
C)2
D)excess

Question 14

Which of the following best describes LiAlH₄ in the reaction scheme shown below?

A)It is a reducing agent.
B)It is an oxidizing agent.
C)It is an acid.
D)It is a base.

Question 15

What is the product of the transformation shown below?

A)
B)
C)
D)

Question 16

What would be the product of the following reaction?

A)
B)
C)
D)

Question 17

Which of the following best describes the relationship between borane and DIBAL?

A)Borane is more electrophilic and more reactive towards carbonyls than DIBAL.
B)Borane is more electrophilic and less reactive towards carbonyls than DIBAL.
C)Borane is less electrophilic and more reactive towards carbonyls than DIBAL.
D)Borane is less electrophilic and less reactive towards carbonyls than DIBAL.

Question 18

What is the role of acid in acid-catalyzed acyl substitution reactions?

A)It protonates the carbonyl oxygen,making the carbon more electrophilic.
B)It protonates the nucleophile,making it more nucleophilic.
C)It protonates the carbonyl oxygen,making the carbon more negatively charged.
D)It makes the solvent more polar,improving the rate of substitution reactions.

Question 19

What is the rate determining step in an S_NAr reaction?

A)deprotonation of the nucleophile
B)nucleophilic attack of the aromatic ring
C)resonance stabilization of the tetrahedral intermediate
D)loss of leaving group

Question 20

What is the major product of the following reaction scheme?

A)
B)
C)
D)

Question 21

What is the major product of the following reaction?

A)
B)
C)
D)No reaction would occur.

Question 22

Which of the following is NOT an intermediate of the reaction shown below?

A)
B)
C)
D)

Question 23

What is the product of the following reaction?

A)
B)
C)
D)

Question 24

What is the major product of the reaction shown below?

A)
B)
C)
D)

Question 25

What is the major product of the reaction shown below?

A)
B)
C)
D)No reaction will occur.

Question 26

Which of the following best describes the set of conditions that can accomplish the transformation shown below?

A)H₃O⁺.propylamine
B)DCC,propylamine
C)1)SOCl₂ 2)excess propylamine
D)Both DCC,propylamine and 1)SOCl₂ 2)excess propylamine will accomplish this transformation.

Question 27

Which of the following reagents will accomplish the transformation shown below?

A)BH₃
B)DIBAL
C)LiAlH₄
D)H₃O⁺/H₂O

Question 28

What is the major product of the reaction shown below?

A)
B)
C)
D)No reaction would occur.

Question 29

What is the rate-determining step of an acid-catalyzed hydrolysis of an ester?

A)protonation of the electrophile
B)breaking of the ð bond and formation of the tetrahedral intermediate
C)breaking of the ó bond and loss of the leaving group
D)protonation of the leaving group

Question 30

What is the major product of the following reaction?

A)
B)
C)
D)No reaction would occur.

Question 31

What is the product (or products)of the transformation shown below?

A)
B)
C)
D)

Question 32

What is the major product of the reaction shown below?

A)
B)
C)
D)

Question 33

What is the major product of the reaction shown below?

A)
B)
C)
D)

Question 34

Which aromatic ring will react faster to an S_NAr reaction and why?

A)I because fluoride is a better leaving group
B)I because fluoride makes the ring more electrophilic
C)II because chloride is a better leaving group
D)II because chloride makes the ring more electrophilic

Question 35

What is the product of the transformation shown below?

A)
B)
C)
D)

Question 36

Which of the following would be the most reactive in an S_NAr reaction?

A)
B)
C)
D)

Question 37

What is the product of the following reaction?

A)
B)
C)
D)

Question 38

What is the major product of the reaction shown below?

A)
B)
C)
D)

Question 39

What is the product of the following reaction?

A)
B)
C)
D)

Question 40

Which of the following best describes the role of the chloride atom in the nucleophilic acyl substitution reaction of an acid chloride?

A)Its high electronegativity draws electron density away from the carbonyl,making it more electrophilic.
B)Its high electronegativity makes it effective at carrying negative charge and makes it a good leaving group.
C)Its easily protonated by acid makes it an effective electrophile for acid catalyzed reactions.
D)Its high electronegativity draws electron density away from the carbonyl and makes it effective at carrying negative charge,making it more electrophilic.

Question 41

The position of an electron withdrawing substituent has no effect on the reactivity of an aromatic ring in an S_NAr reaction.

Question 42

Sodium cyanoborohydride acts as a nucleophile,whereas sodium borohydride acts as a nucleophile.

Question 43

Lithium aluminum hydride coverts an ester to a secondary alcohol.

Question 44

Aryl fluorides are more reactive then aryl chlorides in S_NAr reactions.

Question 45

Reaction of one equivalent of a Grignard reagent with an ester results in a ketone.

Question 46

Borane converts carboxylic acids into aldehydes.

Question 47

Borane acts as a nucleophile,whereas sodium borohydride acts as a nucleophile.

Question 48

Acid protonates the carboxylic acid derivative in nucleophillic acyl substitutions making it more electrophilic.

Question 49

An alkoxide is a better leaving group then a halide.

Question 50

Dimethylaminopyridine is a better catalyst than pyridine in nucleophilic acyl substitution reactions.

Question 51

Dicyclohexylcarbodiimide is a reagent used to form amides and esters from carboxylic acids.

Question 52

A Grignard reaction will reduce an ester to a tertiary alcohol.

Question 53

Acid chlorides are less electrophilic then acid anhydrides.

Question 54

Electron withdrawing groups make an aromatic ring more reactive to S_NAr reactions.

Question 55

Nucleophillic acyl substitutions go through a trigonal planar intermediate.

Question 56

The tetrahedral intermediate is the result of nucleophilic attack on a carbonyl carbon.

Question 57

DIBAL can reduce acid anhydrides into both aldehydes and alcohols.

Question 58

Borane can reduce an amide to either an amine or an aldehyde.

Question 59

An acyl chloride can be reduced by sodium cyanoborohydride.

Question 60

Esters are more electrophilic then amides.

Question 61

Aldehydes and ketones are more reactive to Grignard reagents than esters.

Question 62

DMAP acts as a(n)_______________ in the reaction of an acid chloride with an amine in excess pyridine.

Question 63

In acid catalyzed hydrolysis of an amide,the acid role in the first mechanistic step is to activate the_______________ .

Question 64

Draw the mechanism for the following nucleophilic acyl substitution reaction.Show the role of DMAP (p-dimethylaminopyridine)in the mechanism along with a resonance state that makes it a better catalyst than pyridine.

Question 65

Saponification is the hydrolysis of an ester in _______________ conditions.

Question 66

Predict the product of the following reaction scheme and draw a mechanism to support it.

Question 67

NaNO₂ forms a diazonium salt from a(n)_______________ .

Question 68

DIBAL reduction of an ester maintained at warm temperature produces a alcohol.

Question 69

In an S_NAr reaction,a cyanate substituent acts as an electron _______________ group.

Question 70

DIBAL reduction of an ester maintained at low temperature produces a ketone.

Question 71

Determine a multistep synthetic scheme to produce the following aromatic product from benzene.Show all intermediates.

Question 72

Reduction of an amide with lithium aluminum hydride results in a(n)_______________

Question 73

The rate-determining step of a nucleophilic acyl substitution reaction is the formation of the tetrahedral intermediate.

Question 74

Nucleophilic attack on a carbonyl carbon forms a(n)_______________ intermediate.

Question 75

Determine a multistep synthetic scheme to produce the following aromatic product from benzene.

Question 76

Predict the product of the following reaction scheme and draw a mechanism to support it.

Question 77

When undergoing a nucleophilic acyl substitution reaction,an acid anhydride leaving group is an alcohol.

Question 78

In the reaction of DIBAL with a carboxylic acid,DIBAL acts as a(n)_______________ .

Question 79

In an S_NAr reaction,the aromatic ð bond acts as a(n)_______________

Question 80

An acid chloride can be formed from a carboxylic acid along with _______________ .