3) The delocalized π system in benzene is formed by a cyclic overlap of 6 orbitals. A) s B) p C) sp D) sp2 E) sp3

Transcription

1 Chapter 8 Questions 1) Which of the following statements is incorrect about benzene? A) All of the carbon atoms are sp hybridized. B) It has delocalized electrons. C) The carbon-carbon bond lengths are all the same. D) The carbon-hydrogen bond lengths are all the same. E) All twelve atoms lie in the same plane. 2) Which of the following statements about benzene is correct? A) All of the carbon atoms are sp3 hybridized. B) It has no delocalized electrons. C) The carbon-carbon bond length is longer than that of ethane. D) It is a planar molecule. E) The carbon-hydrogen bonds are not the same length. 3) The delocalized π system in benzene is formed by a cyclic overlap of 6 orbitals. A) s B) p C) sp D) sp2 E) sp3 4) Give the hybridization, shape, and bond angle of a carbon in benzene. 5) Identify the resonance hybrid. A) B) C) D) E) A, B, and C. 6) Which of the following pairs are resonance structures? 1

2 7) Which of the following is not a resonance structure of the species shown? 8) In which of the following does resonance delocalization of electron density not play a role? 2

3 A) allyl cation B) benzyl anion C) CO3 2- D) O3 E) cyclohexyl radical 9) Draw the arrows to go from one resonance structure to another. 10) Draw two other resonance contributors for the following compound: 11) Does the following structures represent different compounds or resonance contributors? 12) Draw the important resonance structure of: 13) Draw the important resonance structures of: 3

4 14) Draw all major resonance contributors of the species below. 15) Draw the arrows to go from one resonance structure to another. 16) Identify the correctly drawn arrows. A) B) C) D) E) 17) Rate the following molecules in decreasing order of stability: 4

5 18) Identify the most stable structure(s). A) B) C) D) E) 19) Which of the following statements concerning resonance contributors and resonance hybrids is not correct? A) The fewer nearly equivalent resonance contributors are in the structure, the greater the resonance energy. B) A resonance hybrid is more stable than the predicted stability of any of its resonance contributors. C) The greater the number of relatively stable resonance contributors, the greater the resonance energy. D) The greater the predicted stability of a resonance contributor, the more it contributes to the resonance hybrid. E) none of the above 20) What is suggested by the fact that benzene's molar heat of hydrogenation is 36 kcal less than three times the molar heat of hydrogenation of cyclohexene? 21) Aromatic molecules contain π electrons. A) no B) 4n + 2 (with n an integer) C) 4n + 2 (where n = 0.5) D) 4n (with n an integer) E) unpaired 22) The following molecule is not aromatic. Why? 23) Is the following molecule aromatic? Explain. 5

6 24) Which of the following is an aromatic hydrocarbon? 25) Which of the following is aromatic? 26) Which of the following is aromatic? A) cyclopentadienyl cation B) 1,3-cyclohexadiene C) cyclobutenyl anion D) 1,3,5-hexatriene E) cycloheptatrienyl cation 27) Provide the structure of indole. 28) Which of the following is an allylic cation? 6

7 29) Which of the following is a benzylic cation? 30) Which of the following is the most stable cation? 31) Which of the following is the most stable diene? 7

8 32) What descriptive term is applied to the type of diene represented by 2,4-hexadiene? A) conjugated diene B) cumulated diene C) isolated diene D) alkynyl diene E) none of the above 33) What descriptive term is applied to the type of diene represented by 1, 5-octadiene? A) conjugated diene B) cumulated diene C) isolated diene D) alkynyl diene E) none of the above 34) Which of the following is a cumulated diene? 35) Which of the following is a conjugated diene? 36) Which of the following compounds is more stable? Explain. 37) Arrange the following unsaturated hydrocarbons in order of decreasing reactivity toward HBr addition: 8

9 38) Identify the most stable carbocation. A) B) C) D) E) 39) Identify the most stable carbocation. A) B) C) D) E) 9

10 40) Which of the following is/are the major product(s) of the following reaction? A) I B) I and II C) I and III D) II E) III 41) Why is phenol a stronger acid than cyclohexanol? 42) Which of the following is/are the main product(s) of the following reaction? CH2 CH CH CH2? A) B) C) D) A and B E) A and C 10

11 43) What is/are the product(s) from the following reaction? A) I only B) II only C) I is minor, II is major D) I is major, II is minor E) equal amounts of I and II 44) What is/are the product(s) of the following reaction? A) I only B) II only C) III only D) I and II E) I and III 45) What compound results from the 1, 4-addition of one equivalent of HBr to 1, 3-butadiene? A) 1-bromo-1-butene B) 2-bromo-2-butene C) 4-bromo-1-butene D) 3-bromo-1-butene E) 1-bromo-2-butene 11

12 46) Provide the structure of the major product which results from 1,2-addition of HBr to the diene shown below. 47) Provide the structure of the major product which results from 1,4-addition of Br2 to the diene shown below. 48) Give the major organic product(s) for the reaction. A) B) C) D) E) 12

13 49) What is the thermodynamic product for the following reaction? A) I B) II C) III D) IV E) V 13

14 50) What is the kinetic product for the following reaction? A) I B) II C) III D) IV E) V 51) What is/are the product(s) from the following reaction? A) II Minor, III Major B) II Major, III Minor C) III only D) I and II E) II and III 14

15 52) What is/are the product(s) from the following reaction? A) I only B) II only C) III only D) I and II E) II and III 53) What is the product from the following reaction? A) I B) II C) III D) IV E) V 15

16 54) Which of the following conjugated dienes would not react with a dieneophile in a Diels- Alder reaction? A) I B) II C) III D) IV E) I and III 55) Which of the following dienes is the most reactive in a Diels-Alder reaction? A) I B) II C) III D) IV E) V 16

17 56) What diene and what dieneophile would be used to synthesize the following compound? A) I B) II C) III D) IV E) V 57) Which of the following terms best describes a Diels-Alder reaction? A) a [4+2] cycloaddition B) a [2+2] cycloaddition C) a sigmatropic rearrangement D) a 1, 3-dipolar cycloaddition E) a substitution reaction 17

18 58) What is the product of the following Diels-Alder reaction? 59) What diene and what dieneophile could be used to prepare the following? 60) Provide the structure of the major organic product in the following reaction. 18