CHAPTER 21 HW: ALDEHYDES + KETONES

Transcription

1 CAPTER 21 W: ALDEYDES + KETES MECLATURE 1. Give the name for each compound (IUPAC or common name). C Structure 2 ame Structure ame 2. Draw each compound. Structure ame dicyclohexyl ketone 1,1,1-trifluoro-3-pentanone (Z)-3,6-dimethyl-3-heptenal SPECTRSCPY 3. In the 1 MR spectrum of butanal, the signal at 2.40 ppm is a triplet of doublets (approximate J s are 2 z and 7 z). Explain the splitting of this signal, including a sketch of a tree diagram. Page 1

2 4. f compounds A-D, C 3 C 3 Br Br Br A B C D Br a. Which compound would have the following 13 C MR spectra (briefly explain)? δ = 165.9, 132.1, 131.5, 129.1, 127.4, 51.5 ppm Which compound would have the following 13 C MR spectra (briefly explain)? δ = 199.8, 140.3, 135.4, 131.5, 131.0, 127.7, 121.2, 28.6 ppm 5. Below are 1 and 13 C MR spectra of a compound with a formula of C 5 8. Determine the structure, then assign the peaks in the 1 MR spectrum PPM PPM Page 2

3 6. Cyclohexanone has a strong signal in its IR spectrum at 1718 cm -1, while 2-cyclohexenone has a strong signal at 1691 cm -1. Both signals represent vibration of the same kind of bond. Explain why the absorption in 2-cyclohexenone is at a lower wavenumber, including resonance structures. 7. An IR is taken of a mixture of the two compounds below. Two strong signals are noted in the mixed IR spectrum at 1666 and 1692 cm -1, representing the carbonyl stretching modes. Which signal corresponds to which compound? Briefly explain. C= Stretch WITTIG REACTI 8. Give the curved arrow mechanism for each reaction. a. C 3 C 2 Br a. PPh 3 nbuli 3 C C PPh 3 3 C C PPh 3 3 C C PPh 3 Page 3

4 8 continued c. PPh 3 9. Draw both stereoisomers that can be formed in this Wittig reaction. Ph 3 P 10. Give the major product of each reaction (one stereoisomer is sufficient). C 3 C 2 C=PPh a. 3 Ph 3 P c. C C 3 PPh 3 d. 2 C PPh Use a Wittig reaction to produce each alkene, starting from an ylide. C 3 C 2 C 2 C 3 a. C C C 3 C 2 Page 4

5 12. Use a Wittig reaction to produce this alkene, starting from an alkyl halide. YDRATES 13. Give the curved arrow mechanism that shows the formation of hydrate under each set of conditions. a. trace - 2 trace Compound E has a higher percentage of hydrate relative to carbonyl in aqueous solution than compound F. Explain this trend, including energy diagrams with your explanation. E F Page 5

6 15. Compound G has a smaller equilibrium constant (K eq ) for hydrate formation than compound. Explain this trend, including energy diagrams with your explanation. 2 C 3 CF 3 G K eq = 1.06 K eq = 2.9 x 10 4 K eq R R 16. In each pair, predict which would have a greater percentage of hydrate relative to carbonyl when the two forms are at equilibrium in water. Briefly explain each answer. Pair A Brief Explanation: Pair B Brief Explanation: Brief Explanation: Pair C C 3 C 3 Brief Explanation: Pair D 3 Page 6

7 ACETALS 17. Give the curved arrow mechanism for this acetal formation reaction. C 2 C 3 + C 2 C 3 C 3 C Explain why acid is catalytic in the formation of an acetal. (Use the mechanism in the previous problem.) 19. Give the curved arrow mechanism for this reaction. + Page 7

8 20. Give the major organic product for each reaction. a. + C 3 C 2 c. + + d. C + C In order to achieve good yields for most acetal formations, they need to be driven by Le Châtelier s Principle. Explain why good yields are easier to achieve when reacting aldehydes than when reacting ketones. 22. Show all organic products of these reactions. a. C 3 + d. C C + 2 e. 3 C C c. + 2 f. 3 C C 3 C Page 8

9 23. Give the curved arrow mechanism for each reaction. a. C 3 C C c. C 2 C C 3 C 2 d. + Page 9

10 24. Milder conditions can be used to hydrolyze acetal J than to hydrolyze acetal K. Explain their difference in reactivity. C 3 C 3 J C 3 K C3 PRTECTIG GRUPS 25. Design a synthesis that uses cyclopentanone and 4-bromobutanal to efficiently produce the aldehyde shown. + Br 26. The following multi-step synthesis converts benzene into a dicarbonyl species. a. Give the reagents needed to complete each step in the sequence. Br Br Br MgBr Briefly explain why the synthesis below does not work well. Cl Cl AlCl 3 AlCl 3 Page 10

11 IMIES + EAMIES 27. Give the curved arrow mechanism for each reaction. a. C 3 2 trace + C3 + 2 C 3 C trace + 3 C C 3 c. 2 2 trace Page 11

12 28. Draw both stereoisomers that can be formed in this reaction. 2 mild acid 29. Give the major organic product for each reaction (one stereoisomer is sufficient). a. C C 3 2 trace + d. trace + 2 (C3 ) 2 p 5 e. trace + c. f. trace + 3 trace Give the curved arrow mechanism for each reaction. a. + C 2 2 C 3 + C 3 C 2 2 Page 12

13 30 continued C 3 C 2 2 c. 3 C C C 3 C Give the major organic product for each reaction. a. C d. Ph C e. + 2 c. C 3 C f. 3 C Ph + 2 Page 13

14 REACTI SUMMARY 32. Give the major organic product for each reaction. a. K a. a 2 cyclopentanone c. + workup c. + C 3 C 2 d. Br a. Li (s) pentanal c. + workup e. Ph 3 P=CC 3 f. abd 4 C 3 C 2 D g. cat. + C 3 C 2 2 h. + 2 i. a. (C 3 C 2 ) 2 CuLi + workup Page 14