Deck 21: Alpha Carbon Chemistry: Enols and Enolates

Question 1

Which one of the following compounds is most likely to favor the enol tautomer over the ketone tautomer?

A) I
B) II
C) III
D) IV
E) V

Answer 1

I

Question 2

Arrange the following indicated hydrogens in decreasing order (most to least) of acidity.

A) I > II > III > IV
B) IV > II > III > I
C) III > II > I > IV
D) II > I > III > IV
E) III > I > II > IV

Answer 2

III > I > II > IV

Question 3

Which of the following is a keto-enol tautomeric pair?

A) I
B) II
C) III
D) IV
E) V

Answer 3

IV

Question 4

Which carbon atom has the most acidic hydrogen in the following compound?

A) I
B) II
C) III
D) IV
E) V

Question 5

Which one of the following compounds is most acidic?

A) ethyl acetoacetate
B) 2-butanone
C) ethyl pentanoate
D) 1-butanol
E) 3-pentanone

Question 6

Explain why the following equilibrium favors the enol tautomer.

Question 7

Which is the most acidic hydrogen in the following compound?

A) I
B) II
C) III
D) IV
E) V

Question 8

Explain why the following equilibrium favors the enol tautomer.

Question 9

Which of the following indicated $\alpha$ -hydrogens is most acidic?

A) I
B) II
C) III
D) IV
E) V

Question 10

Which of the following statements explains the keto-enol equilibrium shown below?

A) simple enols are more stable
B) the enol tautomer is stabilized by the conjugated $\pi$ system
C) the enol tautomer is stabilized by the intramolecular hydrogen bonding
D) the diketone is less coplanar
E) both B and C

Question 11

How many gamma hydrogens are in 2-pentanone?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 12

Which one of the following compounds is most likely to favor the enol tautomer over the ketone tautomer?

A) I
B) II
C) III
D) IV
E) V

Question 13

Which of the following is (are) a keto-enol tautomeric pair(s)?

A) I
B) II
C) III
D) I and II
E) I and III

Question 14

Which one of the following indicated hydrogens is most acidic?

A) I
B) II
C) III
D) IV
E) V

Question 15

Provide the structure of the enol when 3,3,6-trimethyl-4-heptanone is treated with acid.

Question 16

How many alpha hydrogens are in 2-pentanone?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 17

Which of the following is a keto-enol tautomeric pair?

A) I
B) II
C) III
D) IV
E) None of these

Question 18

Which is the most acidic hydrogen in the following compound?

A) I
B) II
C) III
D) IV
E) V

Question 19

Which is the most acidic hydrogen in the following compound?

A) I
B) II
C) III
D) IV
E) V

Question 20

How many beta hydrogens are in 2-pentanone?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 21

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) none of these

Question 22

Provide the reagents necessary to carry out the following conversion.

Question 23

Which of the following bases will completely convert 1,4-cyclohexanedione into an enolate?

A) sodium hydroxide
B) sodium ethoxide
C) LDA
D) sodium hydride
E) both C and D

Question 24

Which of the following compounds would NOT undergo racemization in the presence of a base?

A) I
B) II
C) III
D) IV
E) II and III

Question 25

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) none of these

Question 26

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 27

Which of the following compounds represents an enolate?

A) I
B) II
C) III
D) IV
E) both B and C

Question 28

Provide the reagents necessary to carry out the following conversion.

Question 29

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 30

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 31

Which one of the following compounds would undergo racemization at the $\alpha$ -stereocenter in the presence of a base?

A) I
B) II
C) III
D) IV
E) none of these

Question 32

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 33

Provide both resonance structures of the enolate formed when the following ketone is treated with a base.

Question 34

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) none of these

Question 35

Provide both resonance structures of the enolate formed when the following ester is treated with a base.

Question 36

Provide the structure of the enolate when acetophenone is treated with a strong base.

Question 37

Provide both resonance structures of the enolate formed when the following ketone is treated with a base.

Question 38

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 39

Provide the reagents necessary to carry out the following conversion.

Question 40

Predict the major product for the following reaction and provide a curved arrow mechanism for the formation of the product.

Question 41

Which of the following aldehydes and ketones will give a positive haloform test?

A) 3-heptanone
B) 4-decanone
C) acetone
D) 3-pentanone
E) 3-hexanone

Question 42

Which one of the following is not a possible product when a crossed aldol addition reaction is carried out with ethanal and butanal as reactants?

A) I
B) II
C) III
D) IV
E) V

Question 43

Provide the reactant that would yield m-chlorobenzoic acid using the haloform reaction.

A) I
B) II
C) III
D) IV
E) V

Question 44

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 45

Predict the product for the following reaction.

A) I
B) II
C) III
D) IV
E) no reaction

Question 46

Which of the following ketones will give a positive haloform test?

A) 3-heptanone
B) 3-hexanone
C) cyclohexanone
D) 2-pentanone
E) 2-methyl-3-hexanone

Question 47

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 48

Predict the product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 49

Give the name of the reaction in which a carboxylic acid can undergo alpha halogenation.

Question 50

Predict the product when cyclohexanone reacts with aqueous sodium hydroxide at 100^°C.

A) I
B) II
C) III
D) IV
E) V

Question 51

Which one of the following compounds does not undergo an aldol addition reaction in the presence of aqueous sodium hydroxide?

A) butanal
B) 2-methylbutanal
C) 3-methylpentanal
D) 2,2-dimethylbutanal
E) pentanal

Question 52

Predict the product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 53

Provide the reagents necessary to carry out the following conversion.

Question 54

Predict the major product for the following reaction sequence.

Question 55

Provide the reagents necessary to convert acetophenone to benzoic acid.

A) PCC/CH₂Cl₂
B) 1. NaOH/Br₂
2) H₃O⁺
C) 1. KMnO₄/NaOH/H₂O
2) H₃O⁺
D) 1. Br₂/PBr₃
2) H₂O
E) both B and C

Question 56

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 57

Predict the major product(s) for the following reaction.

A) I
B) II and IV
C) III
D) I and III
E) V

Question 58

Give the organic by-product in a haloform reaction.

Question 59

In an aldol mechanism, the ___________ attacks the aldehyde.

Question 60

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 61

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 62

Provide the reactant(s) that would give the following possible aldol condensation product.

Question 63

Explain why CH₃ONa should not be used for Claisen condensation of ethylbutanoate.

Question 64

Predict the product for the following reaction.

Question 65

Provide the reactants that would give the following aldol condensation product.

A) I
B) II
C) III
D) IV
E) none of these

Question 66

Predict the product(s) for the following reaction.

A) I
B) II
C) III
D) IV
E) all of these

Question 67

Predict the product for the following reaction.

Question 68

Provide the reactant(s) that would give the following aldol condensation product.

A) I
B) II
C) III
D) IV
E) V

Question 69

Identify a reactive starting material in the Claisen condensation.

A) 3-pentanone
B) butanal
C) ethyl butanoate
D) 1-propanol
E) propanoic anhydride

Question 70

Which one of the following is a major product in a Claisen condensation?

A)( $\alpha$ -keto ester)
B) ( $\beta$ -keto ester)
C) ( $\beta$ -hydroxy ester)
D)( $\gamma$ -hydroxyester)
E) ( $\beta$ -diketone)

Question 71

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 72

Provide the reactants that would give the following aldol condensation product.

Question 73

Provide the reactant(s) that would give the following aldol condensation product.

A) I
B) II
C) III
D) IV
E) V

Question 74

Provide the reactant(s) that would give the following possible aldol condensation product.

A) I
B) II
C) III
D) IV
E) V

Question 75

Provide the structure of reactant (X) for the following reaction.

A) I
B) II
C) III
D) IV
E) V

Question 76

Provide the reactants that would give the following aldol condensation product.

A) I
B) II
C) III
D) IV
E) none of these

Question 77

Predict the major product for the following reaction.

Question 78

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) none of these

Question 79

Provide the reactant(s) that would give the following possible aldol condensation product.

Question 80

Predict the major product for the following reaction.

A) I
B) II
C) III
D) IV
E) V