Chem 2425 Test 3 Review

Transcription

1 Name: Class: Date: ID: A Chem 2425 Test 3 Review Draw structures corresponding to each of the given names. 1. cis-1,3-cyclopentanedicarboxylic acid 2. cyanoacetic acid 3. 2-propenamide Provide proper IUPAC names. 4. Name: 5. Name: 6. Name: 7. Name: 8. Name: 1

2 Name: ID: A 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 CN OCH Explain why cyanoacetic acid and methoxyacetic acid are more acidic than their correspondingly substituted benzoic acid counterparts. 10. 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. 11. Explain the differences in acidity between p-methoxybenzoic acid and m-methoxybenzoic acid. Give the major organic product(s) for each of the following reactions or sequences of reactions. Show all relevant stereochemistry

3 Name: ID: A 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. Tollens' Reagent 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 + j. CH 3I f. CrO 3, H 2 SO 4, H 2 O 16. CH 3 CH=CHCH 2 COOH CH 3 COOH + HOOCCH 2 COOH What is the order of decreasing reactivity towards nucleophilic acyl substitution for the carboxylic acid derivatives? (most reactive first) 19. a. I, II, III, IV b. I, III, IV, II c. II, IV, III, I d. II, I, III, IV 20. Write the complete stepwise mechanism for the basic hydrolysis of acetamide, shown below. Show all electron flow with arrows and draw all intermediate structures. 3

4 Name: ID: A Provide structure(s) for the starting material(s), reagent(s) or the major organic product(s) of each of the following reactions or sequences of reactions. Show all relevant stereochemistry

5 Name: ID: A Choose the best reagent(s) from the list provided below for carrying out the following transformations. Place the letter corresponding to the best choice in the blank to the left of the transformation. a. (Ph) 2 CuLi, ether f. 1. DIBAH, toluene b. NaBH 4, ethanol 2. H 3 O + c. 1. CH 3 MgBr, ether g. 1. (Ph) 2 CHMgBr 2. H 3 O + 2. H 3 O + d. 1. LiAlH 4, THF h PhMgBr, ether 2. H 3 O + 2. H 3 O + e. (CH 3 ) 2 CuLi, ether 29. Show how you would accomplish each of the following transformations. More than one step may be required. Show all reagents and all intermediate structures

6 Name: ID: A 32. For each pair of compounds below, tell which spectroscopic technique you would use to distinguish between the two members of the pair. Tell what differences you would expect to see

7 Chem 2425 Test 3 Review Answer Section SHORT ANSWER 1. ANS: 2. ANS: 3. ANS: 4. ANS: phenylacetonitrile or 2-phenylethanenitrile 5. ANS: Ethyl p-aminobenzoate 6. ANS: bis(2-methylpropanoic) anhydride 7. ANS: methyl phenylacetate 8. ANS: N-cyclopentyl-3-methylbutanamide 1

8 9. 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. 10. 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. 2

9 11. 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. 12. ANS: 13. ANS: 14. ANS: 3

10 15. ANS: 16. ANS: a 17. ANS: g 18. ANS: e 19. ANS: b 20. ANS: 21. ANS: 4

11 22. ANS: 23. ANS: 24. ANS: 25. ANS: 26. ANS: 5

12 27. ANS: 28. ANS: 29. ANS: a 30. ANS: 6

13 31. ANS: 32. ANS: 33. ANS: IR 2250 cm 1 (nitrile) cm 1 (four-membered lactam) Although you would not be expected to know the absorption of a four-membered lactam, you should be able to predict that IR spectroscopy would differentiate these two compounds based solely on the nitrile absorption in the first compound and the fact that the lactam would have a carbonyl absorption somewhere in the region of cm ANS: IR 1820, 1760 cm cm 1 (acid OH) (anhydride) cm 1 (carboxyl) 1715 cm 1 (ketone) 1 H NMR one triplet three overlapping triplets one quartet one quartet one singlet 7