chem 2425. chapter 18. ethers and epoxides; thiols and

1 CHEM 2425. Chapter 18. Ethers and Epoxides; Thiols and Sulfides (homework) W

CHEM 2425. Chapter 18. Ethers and Epoxides; Thiols and Sulfides (homework) W

Short Answer

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

1. Draw: tetrahydrofuran

2. Draw: 12-crown-4

3. Draw: 1-isopropoxycyclopentene

4. Draw: allyl benzyl ether

5. Draw: diethyl ether

6. Draw: 3-methyl-1-butanethiol

7. Draw: cyclopropyl ethyl sulfide

IUPAC Naming Instructions: Provide proper IUPAC names.

8. Name:

9. Name:

10. Name:

Exhibit 18-1

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


11. Refer to Exhibit 18-1. Write the complete stepwise mechanism for the reaction. Show all intermediate

structures and all electron flow with arrows.

12. Refer to Exhibit 18-1. Mechanistically, the Williamson ether synthesis outlined above is:

a. an E1 process

b. an SN1 process

c. an E2 process

d. an SN2 process

13. Refer to Exhibit 18-1. Alternatively, cyclopentyl methyl ether may be synthesized from cyclopentene. Outline

a synthesis of cyclopentyl methyl ether from cyclopentene.

14. Diphenyl ether is inert to cleavage by HI or HBr. Explain.

15. Write the complete stepwise mechanism for the reaction below. Show all electron flow with arrows and draw

all intermediate structures.

Exhibit 18-2

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

Acetals are a special class of ethers which have two ether linkages at a single carbon. Tetrahydropyranyl

ethers are acetals that are easily cleaved with mild aqueous acids at room temperature to yield alcohols.

16. Refer to Exhibit 18-2. Draw arrows showing the electron flow for this reaction on the structures provided

below.


17. Refer to Exhibit 18-2. This ether cleavage occurs so easily under such mild conditions because the

carbocation intermediate in step two is very stable. Explain why this carbocation is stabilized.

18. When 1,2-epoxypropane is treated with sodium ethoxide in ethanol 1-ethoxy-2-propanol is the major product

while only a trace amount of 2-ethoxy-1-propanol is produced. Explain these results based on the reaction

mechanism.

Exhibit 18-3

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

Epoxides are synthesized industrially in one step by silver oxide air oxidation of ethylene and on a laboratory

scale in one step by treating an alkene with m-chloroperoxybenzoic acid. An alternative two step process

converts alkenes to halohydrins, which are converted by treatment with base to epoxides.

19. Refer to Exhibit 18-3. Show electron flow with arrows on the structures provided below for each step in the

above transformation.


20. Refer to Exhibit 18-3. The synthesis of epoxides by base treatment of halohydrins is an example of an

intramolecular:

a. SN1 reaction

b. hydrolysis reaction

c. dehydration reaction

d. Williamson ether synthesis

Exhibit 18-4

Propose structure(s) for the starting material(s), reagent(s), or major organic product(s) of the following

reactions or sequences of reactions. Show all relevant stereochemistry.

21.

22.

23.


24.

25.

26.

27.

28.

29.

30.


31.

32.

33.

34.

35. Propose a synthesis of 1,4-dioxane, starting from 1,2-dibromoethane as the only source of carbon.

36. Choose the best reagent for carrying out the following reactions from the list below. Place the letter of the

reagent(s) in the box over the reaction arrow. Use only one letter per box.


A. NaH, then CH3I B. NaOCH3, CH3OH

C. m-ClC6H4CO3H D. CH3MgBr in ether, then H3O+

E. warm H2SO4/H2O F. Hg(O2CCF3)2, CH3OH

G. H2/Pd H. PCC, CH2Cl2

I. Cl2, H2O J. LiAlH4 in ether, then H3O+

37. Complete the synthetic sequence below by drawing the structures of the reaction in the boxes provided.

38. Show how the ether below could be prepared from toluene and any other necessary reagents. Show all

reagents and all intermediate structures.

39. Propose a synthesis for the following compound using benzene or toluene and any other reagents necessary.

Show all major intermediate compounds that would probably be isolated during the course of your synthesis.


40. Name the compound shown below. Atoms other than carbon and hydrogen are labeled.

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

42. Predict the product of the following reaction.

43. Draw the structure of the ether that could be used to produce the following compound

.

Multiple Choice

Identify the choice that best completes the statement or answers the question.


____ 44. Although not always evident in an IR spectrum, which peak in the IR spectrum below might be due to the

C—O stretch of an ether?

a. 3

b. 1

c. 4

d. 2

____ 45. The following is the proton NMR of a symmetrical alkyl ether. Which peak is most likely due to the protons

adjacent to the ether oxygen atom?

a. 1

b. 3

c. 2

____ 46. How many peaks would appear in the 13

CNMR for the following compound? Atoms other than carbon and

hydrogen are labeled.


a. 6

b. 4

c. 9

d. 5

e. 7

f. 8

____ 47. Consider the following species. Atoms other than carbon and hydrogen are labeled.

Which of the following would be produced upon treatment with I2,?

a.

b.

c.


d.

____ 48. What is the product formed upon treatment of the following substance with hydrogen peroxide at room

temperature, followed by treatment with a peroxyacid? Atoms other than carbon and hydrogen are labeled.

a.

b.

c.

d.

____ 49. Which of the following will undergo rearrangement upon heating?

a. 2-pentenyl phenyl ether


b. 1-propenyl 2-propenyl ether

c. 2-butenyl phenyl ether

d. All will undergo rearrangement.


CHEM 2425. Chapter 18. Ethers and Epoxides; Thiols and Sulfides (homework) W

Answer Section

SHORT ANSWER

1. ANS:

PTS: 1

2. ANS:

PTS: 1

3. ANS:

PTS: 1

4. ANS:

PTS: 1

5. ANS:

CH3CH2OCH2CH3

PTS: 1

6. ANS:

PTS: 1


7. ANS:

PTS: 1

8. ANS:

m-chloroanisole or m-chloromethoxybenzene or (m-chlorophenyl) methyl ether

PTS: 1

9. ANS:

1-ethoxy-2,2-dimethylpropane or ethyl neopentyl ether

PTS: 1

10. ANS:

dicyclohexyl sulfide

PTS: 1

11. ANS:

PTS: 1

12. ANS:

d

PTS: 1

13. ANS:

PTS: 1

14. ANS:

Acidic ether cleavages are typical nucleophilic substitution reactions that take place by either an SN1 or SN2

pathway. Diaryl ethers like diphenyl ether are inert under ordinary acidic conditions because the generation of

an aryl cation is an SN1 process that is energetically unfavorable, and "back-side" attack at the ring carbon

bound to oxygen is sterically unfavorable.

PTS: 1

15. ANS:


PTS: 1

16. ANS:

PTS: 1

17. ANS:

The carbocation generated in the first step of the SN1 process is resonance-stabilized by the adjacent oxygen

lone pairs.

PTS: 1

18. ANS:

Basic nucleophiles like ethoxide react with epoxides in a typical SN2-type process, so attack takes place at the

less hindered epoxide carbon.


PTS: 1

19. ANS:

PTS: 1

20. ANS:

d

PTS: 1

21. ANS:

PTS: 1

22. ANS:

PTS: 1

23. ANS:

PTS: 1


24. ANS:

PTS: 1

25. ANS:

PTS: 1

26. ANS:

PTS: 1

27. ANS:

PTS: 1

28. ANS:

PTS: 1

29. ANS:


PTS: 1

30. ANS:

PTS: 1

31. ANS:

PTS: 1

32. ANS:

PTS: 1

33. ANS:

PTS: 1

34. ANS:


PTS: 1

35. ANS:

PTS: 1

36. ANS:

PTS: 1

37. ANS:

PTS: 1

38. ANS:


PTS: 1

39. ANS:

PTS: 1

40. ANS:

Ethyl hexyl ether or 1-ethyoxyhexane

PTS: 1

41. ANS:

o-mercaptotoluene

PTS: 1

42. ANS:

PTS: 1

43. ANS:


PTS: 1

MULTIPLE CHOICE

44. ANS: D PTS: 1

45. ANS: B PTS: 1

46. ANS: F PTS: 1

47. ANS: C PTS: 1

48. ANS: A PTS: 1

49. ANS: D PTS: 1

chem 2425. chapter 18. ethers and epoxides; thiols and

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