CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W Short Answer Drawing Instructions: Draw structures corresponding to each of the given names. 1. Draw: 2-propylpentanoic acid 2. Draw: cis-1,3-cyclopentanedicarboxylic acid 3. Draw: cyanoacetic acid 4. Draw: m-chlorobenzoic acid 5. Draw: 2-propenenitrile IUPAC Naming Instructions: Provide proper IUPAC names. 6. Name: 7. Name: 8. Name: 9. Name: 1 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
10. Name: 11. What is the correct name for the following structure? a. 2-oxohexanoic acid b. 5-oxohexanoic acid c. methyl butroxoketone d. 4-ketopentanoic acid Exhibit 20-1 Consider the data in the Table below to answer the following question(s): Acidities of Substituted Benzoic and Acetic Acids pk a s at 25 C Y C 6 H 4 COOH Y Y CH 2 COOH meta para H 4.75 4.19 4.19 CN 2.47 3.64 3.55 OCH 3 3.57 4.09 4.46 12. Refer to Exhibit 20-1. Draw the structure of the strongest acid in the table above. 13. Refer to Exhibit 20-1. Explain why cyanoacetic acid and methoxyacetic acid are more acidic than their correspondingly substituted benzoic acid counterparts. 14. Even through the para position is one carbon farther from the carboxy group than the meta position, p-cyanobenzoic acid is more acidic than m-cyanobenzoic acid. Explain the differences in acidity between p-cyanobenzoic acid and m-cyanobenzoic acid. 15. Explain the differences in acidity between p-methoxybenzoic acid and m-methoxybenzoic acid. Exhibit 20-2 Consider the data below to answer the following question(s). 2 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
When CO 2 is bubbled through an ether solution of benzylmagnesium bromide, and the resulting mixture is acidified, phenylacetic acid is produced. Any unreacted benzylmagnesium bromide is converted to toluene in the acidification step. 16. Refer to Exhibit 20-2. Write the complete reaction sequence for the process described above. 17. Refer to Exhibit 20-2. How could you separate phenylacetic acid from toluene? 18. Refer to Exhibit 20-2. This reaction is described as a process. a. carbonylation b. carboxylation c. carbaniolation d. cationation Exhibit 20-3 What is the order of increasing acidity for the following compounds? (least to most) 19. a. IV, I, III, II b. III, II, I, IV c. II, III, I, IV d. III, II, IV, I 20. a. IV, I, III, II b. IV, II, III, I c. II, III, I, IV d. I, III, II, IV 3 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
21. a. IV, II, I, III b. I, II, IV, III c. III, I, II, IV d. III, IV, II, I Exhibit 20-4 Give the major organic product(s) for each of the following reactions or sequences of reactions. Show all relevant stereochemistry. 22. 23. 24. 25. 26. 27. 4 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
28. 29. Exhibit 20-5 Choose the best reagent(s) for carrying out the following conversions from the list below. Place the letter corresponding to the best choice in the blank to the left of the conversion. a. KMnO 4, H 3 O + g. 1. Mg, ether b. CH 3I 2. CO 2 c. NaBH 4, ethanol 3. H 3 O + d. 1. BH 3 h. 1. NaCN 2. H 3 O + 2. H 2 SO 4, H 2, heat e. 1. CH 3 MgBr, ether i. O 3, then Zn and HOAc 2. H 3 O + f. CrO 3, H 2 SO 4, H 2 O 30. CH 3 CH=CHCH 2 COOH CH 3 COOH + HOOCCH 2 COOH 31. 32. 33. Exhibit 20-6 Carboxylic acids are synthesized from alkyl halides via Grignard reagent carboxylation or nitrile hydrolysis. Choose the best method for effecting each of the following conversions. Explain each of your choices. If neither method is appropriate, explain. 5 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
34. 35. 36. 37. Propose a synthesis of the anti-inflammatory drug Ibuprofen from benzene. Show all reagents and all intermediate structures. Assume that ortho and para isomers can be separated. Exhibit 20-7 Show how you would accomplish the following transformations. More than one step may be required. Show all reagents and all intermediate structures. 38. 39. Name the following substance. Atoms other than carbon and hydrogen are labeled. 40. Name the following substance. Atoms other than carbon and hydrogen are labeled. 6 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
7 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W Answer Section SHORT ANSWER 1. ANS: 2. ANS: 3. ANS: 4. ANS: 5. ANS: 6. ANS: 1,5-pentanedioic acid 8 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
7. ANS: o-hydroxybenzoic acid 8. ANS: 5,5-dimethyl-1,3,6-cycloheptatriene-1-carboxylic acid 9. ANS: (E)-2-methyl-2-butenoic acid 10. ANS: phenylacetonitrile or 2-phenylethanenitrile 11. ANS: b 12. ANS: NC CH 2 COOH 13. ANS: Electron-withdrawing groups, like CN and OCH 3, inductively withdraw electron density, which stabilizes the resulting carboxylate anion and, thus, increases the acidity of the carboxylic acid. These inductive effects are strongly dependent on distance. The CN and OCH 3 substituents are closer to the carboxylate in the substituted acetic acids than in the substituted benzoic acids, so their effect is greater. 14. ANS: In p-cyanobenzoic acid, the negative charge of the carboxylate can be better stabilized than in the meta isomer because the electron-withdrawing cyano group polarizes the benzene ring and places a positive charge next to the negatively charged carboxyl group. The same polarization occurs in m-cyanobenzoic acid, but the effect is not as great because the charge is one carbon farther away from the carboxy group. 9 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
15. ANS: p-methoxybenzoic acid is less acidic than m-methoxybenzoic acid because the carboxyl group is directly conjugated, through the benzene ring, with the electron-donating oxygen lone pairs of the methoxy group. This destabilizes the p-methoxybenzoate anion relative to the m-methoxybenzoate anion by placing two negative charges on the carboxylate group. 16. ANS: 17. ANS: 10 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
Extract the ether solution containing the mixture of products with a dilute aqueous solution of sodium hydroxide. This converts phenylacetic acid to its carboxylate salt, which will dissolve in the aqueous layer. The toluene will remain in the ether layer. Separate the aqueous and organic layers, acidify the aqueous layer, and extract with an organic solvent to recover the phenylacetic acid. 18. ANS: b 19. ANS: b 20. ANS: a 21. ANS: c 22. ANS: 23. ANS: 24. ANS: 25. ANS: 11 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
26. ANS: 27. ANS: 28. ANS: 29. ANS: 30. ANS: a 31. ANS: g 32. ANS: f 33. ANS: e 34. ANS: 12 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
Since S N 2 displacements do not occur at tertiary alkyl halides the Grignard reagent carboxylation is the best method for carrying out this conversion. 35. ANS: Amine protons interfere with the formation of Grignard reagents, so nitrile hydrolysis is the best method for carrying out this conversion. 36. ANS: Either method would be appropriate for this conversion. 37. ANS: 38. ANS: 13 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W
39. ANS: 4-hydroxy-2,2-dimethylbutanoic acid 40. ANS: 3-methylbutanenitrile 14 CHEM 2425. Chapter 20. Carboxylic Acids and Nitriles (homework) W