Deck 22: Carbonyl Alpha-Substitution Reactions

Question 1

Exhibit 22-3
Consider the reaction below to answer the following question(s).
Refer to Exhibit 22-3.The enolate ion in the reaction is:

Answer 1

C

Question 2

Exhibit 22-1
Refer to the compounds below to answer the following question(s):
Indicate which hydrogens in Compound II are the most acidic.Explain your answer.

Answer 2

The methylene hydrogens are the most acidic because they are flanked by two electron-withdrawing groups,−NO₂ and C=O.The enolate generated by their removal is highly resonance stabilized;it has three resonance forms. In contrast,the enolate generated by the abstraction of a methyl proton is stabilized by only one electron-withdrawing group and has two resonance forms:

Question 3

Exhibit 22-4
Consider the reaction sequence below to answer the following question(s):
Refer to Exhibit 22-4.Write the complete stepwise mechanism for the conversion of Compound X into Compound Y.Show all electron flow with arrows and draw all intermediate structures.

Answer 3

Question 4

Exhibit 22-1
Refer to the compounds below to answer the following question(s):
Refer to Exhibit 22-1.Draw the structures for all enols of Compound I.

Question 5

Exhibit 22-5
Consider the reaction sequence below to answer the following question(s):
Refer to Exhibit 22-5.Conversion of B into C involves hydrolysis of the ester followed by decarboxylation.On the structures provided below,show the electron flow for the decarboxylation step.

Question 6

Exhibit 22-2
Consider the structures below to answer the following question(s).
Refer to Exhibit 22-2.Indicate the most acidic hydrogens in each of the molecules.

Question 7

Exhibit 22-1
Refer to the compounds below to answer the following question(s):
Refer to Exhibit 22-1.Choose the most acidic compound from Compounds I - IV.Explain your choice.

Question 8

Exhibit 22-1
Refer to the compounds below to answer the following question(s):
Refer to Exhibit 22-1.Indicate all the acidic hydrogens in Compounds I through IV.

Question 9

Exhibit 22-5
Consider the reaction sequence below to answer the following question(s):
Refer to Exhibit 22-5.The starting material A in this reaction sequence is called _____.

A)a β-keto ester
B)an α-carboethoxy ketone
C)a malonic ester
D)an acetoacetic ester

Question 10

Exhibit 22-3
Consider the reaction below to answer the following question(s).
Refer to Exhibit 22-3.The weakest acid in the reaction is:

Question 11

Exhibit 22-3
Consider the reaction below to answer the following question(s).
Refer to Exhibit 22-3.On the structures provided above,draw arrows indicating electron flow in the generation of the intermediate C.

Question 12

Exhibit 22-2
Consider the structures below to answer the following question(s).
Rank the molecules above in order of increasing acidity (least acidic to most acidic).

A)III,II,I
B)II,III,I
C)I,II,III
D)II,I,III

Question 13

Exhibit 22-6
Consider the reaction below to answer the following question(s):
Refer to Exhibit 22-6.Write the complete stepwise mechanism for the reaction above.Show all intermediate structures and all electron flow with arrows.

Question 14

Exhibit 22-6
Consider the reaction below to answer the following question(s):
Refer to Exhibit 22-6.Explain the product ratio in this reaction.

Question 15

Exhibit 22-5
Consider the reaction sequence below to answer the following question(s):
Refer to Exhibit 22-5.Conversion of A into B is a type of reaction termed _____.

A)an acylation
B)an enolation
C)an alkylation
D)a phenylation

Question 16

Exhibit 22-4
Consider the reaction sequence below to answer the following question(s):
Refer to Exhibit 22-4.Below are the structures and electron flow for the conversion of Compound Y into Compound Z.Draw the structure of Compound Z.(Hint: Compound Z is an alcohol. )

Question 17

Exhibit 22-3
Consider the reaction below to answer the following question(s).
Refer to Exhibit 22-3.The strongest base in the reaction is:

Question 18

Exhibit 22-5
Consider the reaction sequence below to answer the following question(s):
Refer to Exhibit 22-5.The initial product formed on decarboxylation is an enol,which rapidly equilibrates to its keto form under the acidic reaction conditions.Write the complete stepwise mechanism for the acid-catalyzed conversion of the enol into its keto form,Compound C.

Question 19

Exhibit 22-4
Consider the reaction sequence below to answer the following question(s):
Refer to Exhibit 22-4.Compound X,diethyl propanedioate,is more commonly known as _____.

A)ethyl acetoacetate
B)acetoacetic ester
C)oxalic ester
D)malonic ester

Question 20

Nitroethane [CH₃CH₂NO₂,pK_a = 8.6] is a much stronger acid than ethane [CH₃CH₃,pK_a ≈ 60].Explain.

Question 21

Explain how to use an alkylation reaction to produce: from Atoms other than carbon and hydrogen are labeled.

Question 22

The alkyl halide that should be used to produce octanoic acid via the malonic ester synthesis is:

A)1-bromooctane
B)1-bromohexane
C)1-bromopentane
D)1-bromodecane
E)1-bromoundecane

Question 23

​Draw the mechanism of the acid-catalyzed chlorination of acetophenone in the presence of a base.

Question 24

Draw the structure of the major product formed when the substance represented by the following molecular model is treated with: 1.Br₂/acetic acid,2.pyridine/heat.Atoms of other than carbon and hydrogen are labeled.

Question 25

Explain why the following reaction does not occur to any significant extent respect when the reactant is treated with bromine in the presence of acetic acid.Atoms other than carbon and hydrogen are labeled.
​
​ Reactant Product

Question 26

​Draw the mechanism of enol formation from acetone in a reaction catalyzed by hydrochloric acid.

Question 27

Examine the following generalized structure. This represents

A)the acid catalyzed intermediate between an keto and enol tautomer.
B)the base catalyzed intermediate between an keto and enol tautomer.
C)one of the resonance forms of the acid catalyzed intermediate between an keto and enol tautomer.
D)one of the resonance forms of the acid catalyzed intermediate between an keto and enol tautomer..

Question 28

​Draw the general mechanism of the α-substitution reaction between acetone and the electrophilic methyl group.

Question 29

Write the complete stepwise mechanism for the reaction of cyclopentanone with bromine in acetic acid to give 2-bromocyclopentanone.Show all intermediate structures and all electron flow with arrows.

Question 30

Which of the hydrogen atoms indicated by a number is the most acidic in the structure below? Atoms other than carbon and hydrogen are labeled.

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

Question 31

The following substance is produced using acetoacetic ester synthesis.Atoms other than carbon and hydrogen are labeled. Which of the following regions of an IR spectrum could be used to monitor the progress of the reaction?

A)2850 - 29060 cm^-1
B)2500 - 3100 cm^-1
C)1670 - 1780 cm^-1
D)500 - 600 cm^-1
E)either c or d

Question 32

Using the acetoacetic ester synthesis,to produce 5-methyl-2-heptanone,the alkyl halide that should be used is:

A)1-bromo-2-methylpentane
B)1-bromo-2-methylnonane
C)1-bromo-2-methylbutane
D)1-bromo-2-methyldecane
E)1-bromo-5-methylheptane

Question 33

Which of the following is not correct?

A)Tautomers are constitutional isomers.
B)Tautomers rapidly interconvert.
C)The enol form is generally more stable.
D)Tautomerization is catalyzed by both acids and bases.
E)All of the above are correct with respect to tautomers.