CHEM 2425. Chapter 24. Amines and Heterocycles …

1 CHEM 2425. Chapter 24. Amines and Heterocycles (homework) W

CHEM 2425. Chapter 24. Amines and Heterocycles (homework) W

Short Answer

Exhibit 24-1

Classify each of the following nitrogen atoms in the following compounds as primary, secondary, tertiary, or

quaternary.

1.

2.

3.

4.

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

5. Draw: diisopropylamine

6. Draw: N,N-dimethylcyclopentanamine

7. Draw: 1,4-butanediamine

IUPAC Naming Instructions: Provide proper IUPAC names.


8. Name:

9. Name:

10. Name:

11. Name:

12. Name:

Exhibit 24-2

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

Methamphetamine can be synthesized by reacting phenyl-2-propanone with methylamine in the presence of

H2/Ni.


13. Refer to Exhibit 24-2. Identify the nucleophile in the initial reaction of phenyl-2-propanone to yield

intermediate A.

14. Refer to Exhibit 24-2. Although the yield of methamphetamine is good, some unreacted phenyl-2-propanone

remains after the reaction is complete. Describe how methamphetamine can be separated from

phenyl-2-propanone.

Exhibit 24-3

Refer to the Table of pKas below to answer the following question(s):

pKas of Some Arylammonium Ions

Y pKa

H 4.63

1.74

NH2 6.15

15. Refer to Exhibit 24-3. Explain the difference in acidity between p-cyanoanilinium ion and anilinium ion. Use

both words and structures.

16. Refer to Exhibit 24-3. Explain the difference in acidity between p-aminoanilinium ion and anilinium ion. Use

both words and structures.

17. Rank the following compounds in order of increasing basicity. Label the least basic compound "1" and the

most basic compound "4". Place the number corresponding to the compound's rank in the blank below the

compound.

18. When a THF solution of phenyl-2-propanone and bromobutane is treated with 50% aqueous NaOH, poor

yields of 3-phenyl-2-heptanone result. However, when a small amount of benzyltriethylammonium chloride is

added to the reaction mixture, the yield of 3-phenyl-2-heptanone increases to 90%. Explain these results.


Exhibit 24-4

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

19. Refer to Exhibit 24-4. Draw arrows on the structures provided below which show electron flow in the

complete stepwise mechanism for the reaction above.

20. Refer to Exhibit 24-4. This reaction is an example of:

a. a Curtius rearrangement

b. a Hofmann elimination reaction

c. a Gabriel synthesis


d. a Hofmann rearrangement

Exhibit 24-5

Give the major organic product(s) of each 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.

Exhibit 24-6

Show how each of the following transformations might be best accomplished. More than one step may be

required. Show all reagents and all intermediate structures.


34.

35.

36.

37.

Exhibit 24-7

Choose the best series of reactions for accomplishing each conversion below.

38.

a.

b.

c.

d.


39. Mescaline is a hallucinogenic alkaloid isolated from peyote cactus. Synthesize mescaline from

3,4,5-trimethoxytoluene. Show all reagents and all intermediate structures.

Exhibit 24-8

Refer to the data below to answer the following question(s):

Triclocarban is a disinfectant prepared from 3,4-dichloroaniline and 4-chlorophenylisocyanate.

40. Refer to Exhibit 24-8. Prepare 4-chlorophenylisocyanate from toluene.

41. Refer to Exhibit 24-8. Prepare 3,4-dichloroaniline from benzene.

42. Draw the structures for each of the intermediates in the boxes provided for the synthesis below.


43. Name the following substance. Atoms other than carbon and hydrogen are labeled.

44. Draw the product of the reaction of the following substance with 1.) LiAlH4 in ether, 2.) H2O with the

following substance. From what alkyl bromide could this substance be produced when reacted with NaCN?

Atoms other than carbon and hydrogen are labeled.


45. Write the equation for the reaction represented by the pKa of methyl amine.


CHEM 2425. Chapter 24. Amines and Heterocycles (homework) W

Answer Section

SHORT ANSWER

1. ANS:

The nitrogen atom in ephedrine is secondary.

PTS: 1

2. ANS:

The nitrogen atom in amphetamine is primary.

PTS: 1

3. ANS:

The nitrogen in mepiquat chloride is a quaternary ammonium salt.

PTS: 1

4. ANS:

The nitrogen atom in fexofenadine is tertiary

PTS: 1

5. ANS:

PTS: 1

6. ANS:

PTS: 1

7. ANS:

H2NCH2CH2CH2CH2NH2

PTS: 1

8. ANS:

N-isopropyll-N-methylcyclobutylamine

PTS: 1

9. ANS:


2,4-hexanediamine

PTS: 1

10. ANS:

methyl 2-aminobutanoate

PTS: 1

11. ANS:

N-ethylaniline

PTS: 1

12. ANS:

p-nitroaniline

PTS: 1

13. ANS:

The nucleophile is methylamine.

PTS: 1

14. ANS:

Dissolve the reaction mixture containing the ketone and amine in ether and extract with aqueous HCl. The

basic amine will dissolve in the aqueous layer as its hydrochloric salt. The neutral ketone will remain in the

ether layer. Separate the two layers and neutralize the aqueous layer with NaOH. Extract the neutralized layer

with ether. The purified amine will dissolve in the ether.

PTS: 1

15. ANS:

p-Cyanoanilinium ion is a stronger acid (pKa = 1.74) than anilinium ion (pKa = 4.63). p-Cyanoanilinium ion

gives up a proton on nitrogen more readily than anilinium ion because the electron-withdrawing cyano group

polarizes the benzene ring and thus decreases the stability of the positively charged ion.

PTS: 1

16. ANS:

p-Aminoanilinium ion (pKa = 6.15) is less acidic than anilinium ion (pKa = 4.63) because p-aminoanilinium

ion is stabilized by the electron-donating amino group. The p-amino group donates electron density to the

benzene ring, which helps stabilize the positive charge on nitrogen.


PTS: 1

17. ANS:

PTS: 1

18. ANS:

The reaction that is occurring is a carbonyl -substitution reaction. Hydroxide ion abstracts a proton from C-l

on phenyl-2-propanone to generate an enolate ion, which then undergoes SN2 attack at the primary carbon of

bromobutane. However, since the organic layer and water layer are immiscible, the hydroxide is unable to

come into contact with the ketone in the organic phase, so there is little or no reaction.

When the quaternary ammonium salt is added, it dissolves in both the aqueous and organic layers. When it

moves into the organic layer, it takes hydroxide ion with it, to preserve the charge neutrality. Once in the

organic layer, hydroxide ion reacts with the ketone to generate the enolate, which then undergoes SN2

displacement of bromide to give the carbonyl -substitution product.

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:

c

PTS: 1

39. ANS:

PTS: 1

40. ANS:

PTS: 1

41. ANS:


PTS: 1

42. ANS:

PTS: 1

43. ANS:

N,N-dimethylbutylamine

PTS: 1

44. ANS:

PTS: 1

45. ANS:

PTS: 1

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CHEM 2425. Chapter 24. Amines and Heterocycles …