1. Which of the following reactions would have the smallest energy of activation?.

Transcription

1 Name: Date: 1. Which of the following reactions would have the smallest energy of activation?. A) B) + +. C) D) E) Which of the following reactions would have the smallest energy of activation? A) C4 + C3 + B) C3C3 + C3C2 + C) D) C + CC E) C C C 2 + Page 1

2 3. Which is not an example of resonance? I C 2 =C C 2.. C 2 C=C 2 + II C 2 C 2 III C IV C 2 =C C C 2 C 3. E) None of these are examples of resonance. C 2 C=C C 2 C 3 4. Which of these dienes can undergo the Diels-Alder reaction? A) 1,2-eptadiene B) 1,3-eptadiene C) 1,4-eptadiene D) 1,5-eptadiene E) 1,6-eptadiene 5. In which case is the indicated unshared pair of electrons NT a contributor to the π aromatic system? N N I II III IV E) None of these Page 2

3 6. Which of the following would you expect to be aromatic? I II III IV V 7. In the presence of light, ethane (1 mol) reacts with chlorine (1 mol) to form which product(s)? A) C2C2 B) C3C2 C) C3C2 D) C2C2 E) All of these 8. Which of the reactions listed below would be exothermic? A) C3 C3 2C3 B) C3 + C4 C4 + C3 C) 2(C3)2C (C3)2C C(C3)2 D) + (C3)3C (C3)3C + E) None of the above 9. Which diene would you expect to react most rapidly with maleic anhydride? C C I II III IV V Page 3

4 10. The p-orbital of a methyl radical carbon, C3, contains how many electrons? A) 1 B) 2 C) 3 D) 4 E) Which of the following contributors to the resonance stabilized hybrid formed when aniline undergoes para-chlorination would be exceptionally stable? : N 2 + N 2 : N 2 : N I II III IV E) None of these 12. The carbon-carbon bonds in benzene are: A) of equal length and are shorter than the double bond of ethene. B) of equal length and are intermediate between a double bond and a single bond. C) of unequal length and are alternately short and long around the ring. D) due only to p-orbital overlap. E) of equal length and intermediate between the carbon-carbon bond lengths in ethene and ethyne. Page 4

5 13. Which of the following free radicals is the most stable? A) B) C) D) C 2 CC 2 CC 2 C 2 C 2 CC 2 CC E) CC The rate of solvolysis in ethanol is least for which of these compounds? A) C65C2 B) C 6 5 C( ) 2 C) (C65)2C C 6 5 C D) E) (C65)3C 15. Which of the following compounds would be most reactive toward electrophilic substitution? C N 2 I II III IV V Page 5

6 16. Which of the following statements about cyclooctatetraene is NT true? A) The compound rapidly decolorizes 2/C4 solutions. B) The compound rapidly decolorizes aqueous solutions of KMn4. C) The compound readily adds hydrogen. D) The compound is nonplanar. E) The compound is comparable to benzene in stability. 17. Which compound would have the shortest carbon-carbon single bond? A) C3 C3 B) C2=C C3 C) C C C C D) C2=C C C E) C2=C C=C2 18. Which set of conditions does not result in allylic halogenation of an alkene? A) 2 at 400 C B) 2 in C4 at 25 C C) 2, RR,hν D) 2 at low concentration in C4 E) N-omosuccinimide in C4, RR 19. Which alkyl halide would be most reactive in an SN1 reaction? A) C65C2C2C2 B) C 6 5 C 2 C C) C 6 5 C 2 C D) C 6 5 C E) C 6 5 CC 2 Page 6

7 20. What would be the major product of the following reaction? peroxides? R I II III IV V 21. The major product(s), A, of the following reaction, C 2 2, hν o C A C 2 C 2 C 2 C 2 C I II III IV would be: C) A mixture of I and II D) III E) IV 22. (Trifluoromethyl)benzene, C65CF3, will A) nitrate rapidly in the ortho-para positions. B) nitrate slowly in the ortho-para positions. C) nitrate rapidly in the meta position. D) nitrate slowly in the meta position. E) fail to nitrate under any conditions. Page 7

8 23. What is the final product, C, obtained via the following reaction sequence? 2 hν A t-buk t-bu heat B i) B 3,TF ii) 2 2, C I II III IV V 24. Which of the following structures would be aromatic? K -2 2K K I II III IV V Page 8

9 25. Which of the following reactions would yield isopropylbenzene as the major product? A) Benzene C C 2 2 S 4 C B) Benzene 2 S 4 C C) Benzene D) Benzene E) All of these Al 3 C 2 C 2 Al The most resistant compound to the action of hot alkaline KMn4 is: A) Pentane B) 1-Pentene C) 2-Pentene D) 2-Pentyne E) Cyclopentene 27. What is the major product obtained from the following reaction sequence? 2 hν A EtNa Et heat i) 3 ii) Zn, Ac I II III IV V B C Page 9

10 28. What would be the major product of the following reaction? NBS, RR? light I II III IV V 29. Which of the following carbocations would be most stable? A) C 6 5 C 2 C 2 CC 2 B) C 2 C 6 5 C 2 C 2 C C) C 6 5 C 2 C 2 C D) E) C 6 5 C 2 CC C 6 5 CC 2 C Page 10

11 30. Each of the five disubstituted benzenes shown below is nitrated. In which of these cases does the arrow not indicate the chief position of nitration. C NC C N 2 C 2 I II III IV V 31. Which is the major product of the following reaction? + C C? C C C C C C C C C C I II III IV V Page 11

12 32. 4-Chloro-3-nitro-benzaldehyde is: N 2 N 2 2 N I II III N 2 IV N 2 V 33. Which would be the major product(s) of the following reaction? N 3 2 S 4? N 2 N 2 3 S I II D) I and II in roughly equal amounts E) I and III in roughly equal amounts III Page 12

13 34. What is the Birch reduction product of the following reaction? Na, N 3 (l) Et? I II III IV V 35. What would you expect to be the major product obtained from the following reaction? C S 3 2 Fe 3? C C C C S 3 S 3 S 3 I II III IV E) Equal amounts of II and IV S Which of the following dienes would you expect to be the most stable? A) C3C2C=CC2C=CC3 B) C3C=CC=CC2C3 C) C2=CC2C2C2C=C2 D) C2=CC=CC2C2C3 E) C3C2C=C=CC2C3 Page 13

14 37. A good synthesis of ( ) 3 C C would be: A) Benzene B) Benzene C Al 3 ( ) 3 C Al 3 ( ) 3 C Al 3 C Al 3 C C) Benzene Al 3 D) More than one of these E) None of these ( ) 2 C C 2 F 38. Which free radical would be most stable? A) CC C 2 B) C) D) E) C 2 CC 2 C 2 CC 2 C 2 CC C 2 CC 39. Benzene is susceptible to electrophilic attack primarily because of its. Page 14

15 40. Unsymmetrical alkenes give Markovnikov products through the most stable intermediates and anti-markovnikov products through the most stable intermediates. 41. Stereochemically speaking, the Diels-Alder reaction is and occurs with of the dienophile stereochemistry. 42. A covalent bond breaking so that each of the resulting intermediates bears a single unpaired electron is an example of bond cleavage. 43. In a chain-propagating step, one radical. 44. Suggest a reasonable synthetic strategy for the synthesis of 3,5-dinitrobenzyl alcohol from benzaldehyde. 45. In general, there are three steps to an electrophilic aromatic substitution reaction. These are: a) formation of an ; b) reaction with an aromatic ring to form an ; and c) loss of a to reform the aromatic system. 46. The Lewis structures of both pyridine and pyrrole have an electron pair on the nitrogen atom, suggesting that both substances might possess basic properties. owever, only pyridine reacts readily with to form pyridinium chloride, while pyrrole is rather unreactive. Explain clearly, using relevant diagrams to illustrate/clarify your answer. 47. Electron-withdrawing groups decrease the electron density on the aromatic ring, causing it to be less reactive than benzene itself towards EAS. These types of groups are called groups. 48. The Diels-Alder reaction is a cycloaddition between a conjugated and a. 49. What product(s) might be obtained via chain-termination step(s) during the reaction of 2-methylpropene with in presence of peroxides? Page 15

16 50. The difference between the amount of heat actually released upon hydrogenation of benzene and that calculated on the basis of the Kekule structure is called the of benzene. Page 16

17 Answer Key 1. C 2. D 3. C 4. B 5. B 6. E 7. E 8. C 9. D 10. A 11. B 12. B 13. E 14. A 15. A 16. E 17. C 18. B 19. D 20. A 21. E 22. D 23. A 24. B 25. E 26. A 27. E 28. C 29. E 30. C 31. D 32. B 33. A 34. D 35. C 36. B 37. B 38. A 39. exposed π system 40. Carbocation; free-radical 41. stereospecific; retention 42. homolytic 43. generates another Page 17

18 N 3 (excess) S 4 heat benzaldehyde 45. electrophile; arenium ion; proton 2 N N 2 NaB N N 2 3,5-dinitrobenzyl alcohol Ṇ. sp 2 + pyridinium chloride N+ pyridinium chloride 46. N + X.. p N + pyrrole not aromatic electron pair: part of aromatic pi sextet Both pyridine and pyrrole are known to exhibit aromatic properties; the nitrogen atom must therefore be sp 2 hybridized in both cases. In the pyridine molecule, this places the electron pair in an sp 2 hybrid orbital, and not involved in the aromatic π sextet needed for aromatic stability; the electron pair is thus available for reacting with, forming pyridinium chloride, while preserving aromatic stability. By contrast, the electron pair in pyrrole must be placed in the p orbital, since all three sp 2 orbitals are used in sigma bonds with neighboring atoms. This allows the electron pair to contribute to aromatic stability by becoming part of the aromatic sextet. Thus, the electron pair on nitrogen is not available for reacting with, because doing so would destroy the aromaticity of the ring. 47. deactivating 48. diene; dienophile Page 18

19 49. The addition of to 2-methylpropene takes place via the formation of the most stable free radical intermediate, by addition of a bromine atom at C1. Two such radicals can couple together via a termination step to afford 1,4-dibromo-2,2,3,3-teramethylbutane as a minor product. Analogous coupling between this radical and a bromine radical leads to the formation of 1,2-dibromo-2-methylpropane as another minor product. peroxides most stable radical intermediate + + termination steps: radical coupling 50. resonance energy Page 19