pg. 1 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

Short Answer

Drawing Instructions: Draw structures corresponding to each of the given names.

1. Draw: 2,2,2-trichloroethanal (chloral)

2. Draw: benzophenone

3. Draw: trans-3-isopropylcyclohexanecarbaldehyde

4. Draw: 5,5-dimethyl-1,3-cyclohexanedione (dimedone)

IUPAC Naming Instructions: Provide proper IUPAC names.

5. Name:

6. Name:

7. Name:

Exhibit 19-1

Consider the reaction below to answer the following question(s):

8. Refer to Exhibit 19-1. Write the complete stepwise mechanism for the reaction shown above. Show all

intermediate structures and all electron flow with arrows.

9. Refer to Exhibit 19-1. The substance formed on addition of water to an aldehyde or ketone is called a

hydrate or a/an:

pg. 2 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

a. vicinal diol

b. geminal diol

c. acetal

d. ketal

10. Refer to Exhibit 19-1. The exact position of the equilibrium between ketones/aldehydes and their hydrates

depends on the structure of the carbonyl compound. Although the equilibrium favors the carbonyl

compound in most cases, cyclopropanone forms a stable hydrate. Explain this phenomenon based on the

structures of cyclopropanone and its hydrate.

11. Refer to Exhibit 19-1. Many nucleophilic addition reactions of aldehydes and ketones are catalyzed by

acid or base. Bases catalyze hydration by:

a. making the carbonyl group more electrophilic

b. shifting the equilibrium of the reaction

c. making the carbonyl group less electrophilic

d. converting the water to hydroxide ion, a much better nucleophile

Exhibit 19-2

Consider the data below to answer the following question(s).

Cyanohydrins are important intermediates in the synthesis of -hydroxycarboxylic acids from ketones and

aldehydes. The nitrile functional group can be hydrolyzed by aqueous acid to yield a carboxylic acid.

Nitriles can also be hydrolyzed to carboxylic acids using aqueous base. Unfortunately, when a

cyanohydrin is treated with aqueous base the original carbonyl compound is isolated.

12. Refer to Exhibit 19-2. The reaction of an aldehyde with hydrogen cyanide is an example of _____

reaction.

a. a nucleophilic substitution

b. an electrophilic addition

c. an electrophilic substitution

d. a nucleophilic addition

13. Refer to Exhibit 19-2. Identify the electrophile in the reaction of benzaldehyde with hydrogen cyanide.

pg. 3 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

14. Refer to Exhibit 19-2. The reaction of benzaldehyde with hydrogen cyanide is catalyzed by the addition of

a small amount of KCN. Write the complete reaction mechanism for the KCN-catalyzed reaction. Show

all electron flow with arrows and show all intermediate structures.

15. Refer to Exhibit 19-2. Formulate a reasonable mechanism for the reaction of the cyanohydrin of

benzaldeyhe, shown above, with aqueous NaOH. Show all intermediate structures and all electron flow

with arrows.

16. In the Wittig reaction, a phosphorus ylide adds to a ketone or aldehyde to yield an alkene. Write the

complete stepwise mechanism for the Wittig reaction shown below. Show all intermediate structures and

all electron flow with arrows.

Exhibit 19-3

Consider the reaction below to answer the following question(s).

17. Refer to Exhibit 19-3. The catalyst in this reaction is:

18. Refer to Exhibit 19-3. The product of this reaction is called:

a. an ylide

b. an acetal

c. a gem diol

d. a hydrate

19. Refer to Exhibit 19-3. Write the complete stepwise mechanism for this reaction. Show all electron flow

with arrows and show all intermediate structures.

Exhibit 19-5

Give the major organic product(s) for each of the following reactions or sequences of reactions. Show all

relevant stereochemistry.

pg. 4 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

20.

21.

22.

23.

24.

25.

26.

27.

pg. 5 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

28.

Exhibit 19-6

Choose the BEST reagent for carrying out each of the following conversions.

29.

a. LiAlH4, THF

b. NaBH4, ethanol

c. 1. DIBAH, toluene

2. H3O+

d. All of the above work well

30.

a. LiAlH4, ether

b. NaBH4, ethanol

c. CrO3, pyridine

d. H2/Pd

31.

a. 1. PhMgBr, ether

2. H3O+

b. 1. PhCH2MgBr, ether

2. H3O +

c. (C6H5)3P=CHC 6H5, THF

d. Li(C6H5) 2Cu, ether

pg. 6 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

32.

a. 1. PhMgBr, ether

2. H3O+

b. 1. PhCH2MgBr, ether

2. H3O+

c. (C6H5)3P=CHC6H5, THF

d. Li(C6H5)2Cu, ether

33.

a. NaBH4, ethanol

b. CH2PPh3

c. NaOH, H2O

d. All of the above

Exhibit 19-7

Show how the Wittig reaction might be used to prepare each of the following alkenes. Identify the alkyl

halide and the carbonyl components that would be used in each synthesis.

34.

35.

Exhibit 19-8

Show how the following conversions might be accomplished. Show all reagents and all intermediate

structures. More than one step may be required.

36.

pg. 7 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

37.

38.

Exhibit 19-9

Consider the data below to answer the following question(s).

C7H14O

IR: 1715 cm1

MS: M+ at m/z = 114, -cleavage fragment at m/z = 71,

McLafferty rearrangement fragment at m/z = 86. 1H NMR: 0.92 (6H, triplet), 1.59 (4H, multiplet), 2.36 (4H, triplet)

39. Refer to Exhibit 19-9. Calculate the degree of unsaturation for this compound.

40. Refer to Exhibit 19-9. What functional group is indicated by the IR data?

41. Refer to Exhibit 19-9. Interpret the mass spectral data.

42. Refer to Exhibit 19-9. Interpret the 1H NMR data.

Exhibit 19-10

Consider the data below to answer the following question(s).

C7H14O

IR: 1715 cm1

MS: M+ at m/z = 114, -cleavage fragment at m/z = 71,

no McLafferty rearrangement fragment 1H NMR:

pg. 8 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

Spectrum obtained from: SDBSWeb: http://www.aist.go.jp/RIODB/SDBS

43. Refer to Exhibit 19-10. Interpret the mass spectral data for this compound.

44. Refer to Exhibit 19-10. Propose a structure for this compound.

45. Name the following compound. Atoms other than carbon and hydrogen are labeled.

pg. 9 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

Answer Section

SHORT ANSWER

1. ANS:

PTS: 1

2. ANS:

PTS: 1

3. ANS:

PTS: 1

4. ANS:

PTS: 1

5. ANS:

4,8-dimethyl-7-nonen-2-one

PTS: 1

6. ANS:

cis-1,3-cyclopentanedicarbaldehyde

PTS: 1

7. ANS:

5-oxoheptanal

pg. 10 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

PTS: 1

8. ANS:

PTS: 1

9. ANS:

b

PTS: 1

10. ANS:

The carbonyl carbon in cyclopropane is highly strained because the preferred bond angle for an

sp2-hybridized carbon is 120 but the real angle is 60. This angle strain is somewhat relieved when

cyclopropanone is hydratedthe preferred bond angle for an sp3-hybridized carbon is about 109.5.

Going from sp2 to sp3 hybridization relieves angle strain by about 10. Thus, the hydrate of cyclopropane

is more stable than the carbonyl form, and the equilibrium lies to the right in this reaction.

PTS: 1

11. ANS:

d

PTS: 1

12. ANS:

d

PTS: 1

13. ANS:

The benzaldehyde is the electrophile in this reaction.

PTS: 1

14. ANS:

PTS: 1

15. ANS:

PTS: 1

pg. 11 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

16. ANS:

PTS: 1

17. ANS:

C

PTS: 1

18. ANS:

b

PTS: 1

19. ANS:

PTS: 1

20. ANS:

pg. 12 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

PTS: 1

21. ANS:

PTS: 1

22. ANS:

PTS: 1

23. ANS:

PTS: 1

24. ANS:

PTS: 1

25. ANS:

pg. 13 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

PTS: 1

26. ANS:

PTS: 1

27. ANS:

PTS: 1

28. ANS:

PTS: 1

29. ANS:

c

PTS: 1

30. ANS:

b

PTS: 1

31. ANS:

d

PTS: 1

32. ANS:

c

PTS: 1

33. ANS:

a

PTS: 1

pg. 14 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

34. ANS:

PTS: 1

35. ANS:

PTS: 1

36. ANS:

PTS: 1

37. ANS:

PTS: 1

38. ANS:

PTS: 1

39. ANS:

The base formula for C7H14O is C7H14. The formula for the saturated compound is C7H16, so the

compound has one degree of unsaturation.

pg. 15 CHEM 2425. Chapter 19. Aldehydes and Ketones_Nucleophilic Addition Reactions (Homework) W

PTS: 1

40. ANS:

Absorption at 1715 cm1 in the infrared spectrum indicates the presence of a carbonyl compound, most

probably a ketone.

PTS: 1

41. ANS:

A fragment at m/z = 71 indicates a loss of 43, or a propyl group, from -cleavage. A fragment at m/z = 86

indicates a loss of 28, or ethylene, from McLafferty rearrangement (transfer of a hydrogen atom from the

gamma carbon to the carbonyl oxygen with concomitant breaking of the bond between the alpha and beta

carbon).

PTS: 1

42. ANS:

The 1H NMR indicates that there are only three different kinds of hydrogen in the molecule. The 6H

triplet is due to two equivalent CH3 groups next to two equivalent CH2 groups, the 4H triplet is due to two

equivalent CH2 groups next to two other equivalent CH2 groups, shifted by a C=O, and the 4H multiplet is

two equivalent CH2 groups between a CH2 and a CH3.

PTS: 1

43. ANS:

A fragment at m/z = 71 indicates a loss of 43, or a propyl group, from -cleavage. The absence of a

McLafferty rearrangement fragment means that there is no hydrogen atom on a gamma carbon, so the

propyl group must be isopropyl, and not n-propyl.

PTS: 1

44. ANS:

2,4-dimethyl-3-pentanone, (CH3)2CHCOCH(CH3)2

PTS: 1

45. ANS:

1-chloro-3-methyl-2-butanone

PTS: 1