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Practice questions to study organic chemistry...

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Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

Chapter 1: Structure Determines Properties! 1. What is the ground state electron configuration of carbon? A) 1s22s22px1 B) 1s22s22px2 C) 1s22s22px12py1 D) 1s22s22px22py1 Ans: C 2. Which of the following has (have) the same electron configuration as Ne? Na- Mg2+ O2- Mg+ A) Na- and O2- B) Mg2+ and O2Ans: B

C) Mg+ and O2-

D) only Mg2+

3. What is the letter designation given to dumbbell shaped orbitals like the one depicted below?

A) s B) p Ans: B

C) d

D) f

4. What is the charge on the phosphorus ion in Na3P? A) -3 B) -1 C) +1 D) +3 Ans: A 5. Predict which bond is the most polar in ethanol, CH3CH2OH? A) C—C B) C—H C) C—O D) O—H Ans: D 6. Which one of the following is the conjugate base of NH3? A) NH4+ B) H+ C) N3- D) NH2– Ans: D 7. Which one of the following is the ionic compound formed between magnesium and chlorine? A) MgCl B) MgCl2 C) Mg2Cl3 D) MgCl3 Ans: B

Page 1 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

8. Identify the condensed formula of the following structure:

A) (CH3)2CHCHClCH(CH3)2 B) CH3CH(CH3)CHClCH(CH3)2 Ans: C

C) D)

(CH3)2CHCHClC(CH3)3 (CH3)3CCHClCH(CH3)3

9. What is the chemical formula of the following carbon skeleton diagram?

A) C8H14 B) C8H16 Ans: C

C) C8H18

D) C8H20

10. How many hydrogen atoms are there on carbon atoms 1 and 2, respectively, in the structure below?

A) 4, 1 B) 4, 0 Ans: D

C) 3, 1

D) 3, 0

11. How many C3H8O constitutional isomers are possible? A) one B) two C) three D) four Ans: C

Page 2 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

12. Which of the following best describes the relationship between the following two structures?

A) B) C) D) Ans:

identical compounds resonance structures constitutional isomers different compounds with different constitutions A

13. How many constitutional isomers of C4H9Br are possible? A) one B) two C) three D) four Ans: D 14. How many constitutional isomers of C3H6Cl2 are possible? A) three B) four C) five D) six Ans: B 15. What is the formal charge on the carbon atom?

A) +1 B) 0 Ans: C

C) -1

D) -2

Page 3 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

16. Which of the following describes the relationship between the following two structures?

A) B) C) D) Ans:

identical structures resonance forms constitutional isomers different compounds with different compositions A

17. Which of the following describes the relationship between the following two structures?

A) B) C) D) Ans:

identical structures resonance forms constitutional isomers different compounds with different compositions B

18. What is the formal charge on the oxygen atom in the structure below?

A) -1 B) 0 Ans: C

C) +1

D) +2

19. What is the formal charge on the nitrogen atom in the structure below?

A) -1 B) 0 Ans: C

C) +1

D) +2

Page 4 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

20. The formal charges on the nitrogen and oxygen in the following structures are, respectively

A) +1, -1 Ans: B

B) 0, -1

C) +1, 0

D) 0, 0

21. In which of the following compounds would you expect Cl to have a partial positive charge? A) HCl B) CCl4 C) NaCl D) HOCl Ans: D 22. Based on the VSEPR model, which of the following species has (have) a trigonal planar geometry? I. BCl3 II. NH3 III. NO3¯ A) only I B) I and II C) I and III D) I, II, and III Ans: C 23. Based on VSEPR theory, which of the following species has (have) a trigonal pyramidal geometry? I. CO32- II. NH3 III. CH3+ A) only I B) only II C) I and II D) II and III Ans: B 24. Which of the following species has(have) a linear geometry? I. CO2 II. NO2+ III. NO2¯ A) only I B) only II C) I and II D) I, II, and III Ans: C 25. Which of the following molecules would you expect to have a dipole moment? I. CO2 II. HCN III. CHCl3 A) II and III B) only II C) only III D) I, II, and III Ans: A 26. Which of the following molecules would you expect to have a dipole moment? I. CH2Cl2 II. CH3Cl III. CCl4 A) only I B) only II C) I and II D) I, II, and III Ans: C 27. The H—C—H bond angles in ethylene, C2H4, are closest to A) 90o B) 109.5o C) 120o D) 180o Ans: C

Page 5 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

28. The C—C—C bond angle in propane, C3H8, is closest to A) 90o B) 109.5o C) 120o D) 180o Ans: B 29. The C—C—C bond angle in propyne, shown below, is

A) 90o B) 109.5o Ans: D

C) 120o

D) 180o

30. The hybridization of carbon atoms 1, 2, and 3 in the following are, respectively

A) sp, sp, and sp2 B) sp, sp, and sp3 Ans: C

C) D)

sp2, sp2, and sp3 sp2, sp3, and sp3

31. How many pi bonds are present in the following structure?

A) one B) two Ans: C

C) three

D) four

32. The carbon-carbon single bond in the following is formed by the overlap of which two orbitals?

A) sp-sp B) sp2-sp Ans: B

C) sp2-sp2

D) sp2-sp3

33. What are the formal charges of boron and nitrogen, respectively, in the following structure?

A) -1 and +1 Ans: A

B) -1 and 0

C) 0 and +1

D) 0 and 0

Page 6 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

34. Which one of the following is isoelectronic with CO2? A) NO2¯ B) NO2+ C) NO2 D) O3 Ans: B 35. In which of the following does hydrogen have a partial negative charge based on electronegativity? A) BH3 B) CH4 C) NH3 D) H2O Ans: A 36. Which of the following species have a zero formal charge on its carbon atom?

A) I and II Ans: B

B) II and IV

C) III and IV

D) I, II, and III

37. Which one of the following species is formed when diazomethane loses a nitrogen molecule?

diazomethane

A) A B) B C) C D) D Ans: A

Page 7 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

38. Which species is formed when the CH3N2+ cation loses a nitrogen molecule?

A. H3C B. H2C C. H3C • D. H3C A) A B) B C) C D) D Ans: A 39. Give the molecular formula of the compound shown below:

A) C8H16O Ans: D

B) C9H18O C) C10H18O

D) C10H20O

40. The electron pair movement depicted below produces a second resonance form for the species. What is the formal charge on the nitrogen atom for this second resonance form?

A) -2 B) -1 Ans: B

C) 0

D) +1

41. Which statement correctly describes the structures of BH3 and NH3? A) Both are trigonal and planar. B) Both are pyramidal. C) BH3 is trigonal planar and NH3 is trigonal pyramidal. D) BH3 is trigonal pyramidal and NH3 is trigonal planar. Ans: C

Page 8 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

42. Which one of the following is the conjugate acid of ethanol? A) CH3CH2O– B) CH3CH2O+ C) CH3CH2OH2+ D) CH3CH2OH3+ Ans: C 43. In the equilibrium below, the strongest base is: (pKa H2O = 15.7, pKa NH3 = 36)

A) A B) B C) C D) D Ans: B 44. In the equilibrium below, the strongest acid is:

A) A B) B C) C D) D Ans: A

Page 9 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

45. Which one of the following is the strongest base?

A) A B) B C) C D) D Ans: A 46. Which one of the following mechanistically depicts the protonation of methanol by hydrogen bromide?

A) A B) B C) C D) D Ans: A

Page 10 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

47. Which one of the following is the strongest acid? A) FCH2CO2H B) ClCH2CO2H C) BrCH2CO2H Ans: A

Prof. Sivaguru Jayaraman

D) ICH2CO2H

48. Which one of the following has the largest acid equilibrium constant, Ka? A) CH3CO2H B) CH2ClCO2H C) CHCl2CO2H D) CCl3CO2H Ans: D 49. For which of the following does the equilibrium favor reactants.

A) A B) B C) C D) D Ans: C 50. Identify the resonance structure which results from the following "electron pair movements".

A) A B) B C) C D) D Ans: A

Page 11 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

51. A Lewis structure of the azide ion, N3¯, is shown below. The formal charge on the middle nitrogen atom is:

A) +2 B) +1 Ans: B

C) 0

D) –1

52. Identify the species which results from the following movement of electron pairs.

A) A B) B C) C D) D Ans: A

Page 12 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

53. The most stable resonance contributor of this would be:

A) A B) B C) C D) D Ans: B 54. What is the molecular formula of aspirin? O O OH O

A) A B) B C) C D) D Ans: C 55. Which of the following is not identical to the others?

A

B

C

D

A) A B) B C) C D) D Ans: D

Page 13 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

56. Which of the line-bond structures below cannot represent a stable molecule? B.

A.

C.

D.

A) A B) B C) C D) D Ans: C 57. Which of the electron-movement arrows below are NOT valid?

A.

C

C C

C B. C

C C

C C

O D.

C.

C A) A B) B C) C D) D Ans: C 58. What atom would have a formal charge in this structure? B

A

C

O N CH2 O H

D

A) A B) B C) C D) D Ans: D

Page 14 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 1 Structure Determines Properties: Answers

Prof. Sivaguru Jayaraman

59. Rank the following in order of decreasing acidity. (more acidic > less acidic)

O

N

N CH3

HO H

H

I

II

CH3

H

III

IV

A) I > IV > III > II B) III > II > I > IV Ans: A

C) D)

IV > I > II > III I > III > IV > II

60. Using resonance principles, on what atom does acid protonate guanidine? B H D

N

A

C H2N

NH2 C

A) A B) B C) C D) D Ans: B 61. What structure would result from these electron movement arrows? ?

O

+

OH O

O A

O

B

C

D

A) A B) B C) C D) D Ans: C 62. What would be the line-bond structure for (CH3)3CCH2CH(CH3)2?

A

B

C

D

A) A B) B C) C D) D Ans: A

Page 15 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 2 Hydrocarbon Frameworks – Alkanes: Answers

Prof. Sivaguru Jayaraman

Chapter 2: Hydrocarbon Frameworks - Alkanes! 1. Alkanes are characterized by the general molecular formula: A) CnH2n-2 B) CnH2n C) CnH2n+2 D) CnH2n+4 Ans: C 2. Cycloalkanes are characterized by the general molecular formula: A) CnH2n-2 B) CnH2n C) CnH2n+2 D) CnH2n+4 Ans: B 3. The carbon-carbon sigma bond in ethane is formed by overlap of which two orbitals? A) 2p-2p B) sp-sp C) sp2-sp2 D) sp3-sp3 Ans: D 4. What is the IUPAC name of the following compound?

A) 4,4-dimethylpentane B) 1-tert-butylpropane Ans: C

C) D)

2,2-dimethylpentane 1,1,1-trimethylbutane

5. The correct IUPAC name of the following compound is

A) 2-ethyl-3,5-dimethylheptane. B) 6-ethyl-5,5-dimethylheptane. Ans: C

C) D)

3,4,4-trimethyloctane. 5,5,6-trimethyloctane.

6. The common name of the following group is

A) n-butyl. Ans: B

B) sec-butyl.

C) isobutyl.

D) tert-butyl.

Page 1 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 2 Hydrocarbon Frameworks – Alkanes: Answers

Prof. Sivaguru Jayaraman

7. Which one of the following is 2,2,5-trimethylhexane? A) (CH3)2CHCH2C(CH3)3 C) CH3CH2CH(CH3)C(CH3)3 B) (CH3)2CHCH2CH2C(CH3)3 D) (CH3)2CHCH2 CH2CH2C(CH3)3 Ans: B 8. The correct IUPAC name of the following is

A) 2,4,7-trimethylnonane. B) 3,6,8-trimethylnonane. Ans: A

C) D)

7-ethyl-2,4-dimethyloctane. 2-ethyl-5,7-dimethyloctane.

C) D)

5-ethyl-6-methylheptane 4-ethyl-3-methylheptane

C) D)

3-ethyl-1,1-dimethylcyclopentane 4-ethyl-1,1-dimethylcyclopentane

C) D)

methyl groups. both methine and methylene groups.

9. What is the IUPAC name of the following?

A) 5,6-diethylhexane B) 2,3-diethylhexane Ans: D 10. What is the IUPAC name of the following?

A) 1-ethyl-4.4-dimethylcyclopentane B) 1-ethyl-3,3-dimethylcyclopentane Ans: C 11. Cyclohexane is composed of A) methine groups. B) methylene groups. Ans: B

Page 2 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 2 Hydrocarbon Frameworks – Alkanes: Answers

12. All the carbons in cyclopentane are A) primary carbons. B) secondary carbons. Ans: B

Prof. Sivaguru Jayaraman

C) D)

tertiary carbons. quaternary carbons.

13. The correct name of the following compound is

A) (1-methylpropyl)cyclohexane. B) (2-methylpropyl)cyclohexane. Ans: B

C) D)

(2,2-dimethylethyl)cyclohexane. (2,2-dimethylpropyl)cyclohexane.

14. The correct IUPAC name of the following compound is

A) (1-methylhexyl)cyclopentane. B) (1-pentylethyl)cyclopentane. Ans: C

C) D)

2-cyclopentylheptane. 1-cyclopentyl-2-heptane.

15. The C—C sigma bond in acetylene is formed by the overlap of which two orbitals?

A) 2p-2p Ans: B

B) sp-sp

C) sp2-sp2

D) sp3-sp3

16. The boiling point of isobutane (-10.2°C) is lower than n-butane (-0.4°C) because isobutane has A) weaker intermolecular van der Waals forces. B) stronger intermolecular van der Waals forces. C) weaker dipole-dipole attractive forces. D) stronger dipole-dipole attractive forces. Ans: A

Page 3 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 2 Hydrocarbon Frameworks – Alkanes: Answers

Prof. Sivaguru Jayaraman

17. Which of the following are constitutional isomers?

A) I, II, and III B) I, III, and IV Ans: A

C) D)

only I and III all are constitutional isomers

18. Arrange the following isomeric alkanes in order of increasing boiling point. I. n-heptane II. 2,3-dimethylpentane III. 2,2,3-trimethylbutane A) I < II < III B) II < III < I C) III < I < II D) III < II < I Ans: D 19. The oxidation states of carbon range from A) 0 to +2. B) 0 to +4. C) –4 to 0. D) –4 to +4. Ans: D 20. Which of the following has(have) a higher oxidation state of carbon than the carbon in formaldehyde, H2C=O? I. CH3OH II. HCO2H III. H2CO3 A) I B) III C) II and III D) I, II, and III Ans: C 21. The tert-butyl group can also be called A) 1,1-dimethylpropyl. B) 1,1-dimethylethyl. Ans: B

C) D)

2,2-dimethylpropyl. 2,2-dimethylethyl.

Page 4 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 2 Hydrocarbon Frameworks – Alkanes: Answers

Prof. Sivaguru Jayaraman

22. Carbon atoms 1, 2, and 3 in the following structure are classified, respectively, as

A) tertiary, primary, secondary. B) quaternary, primary, tertiary. Ans: D

C) D)

quaternary, secondary, secondary. quaternary, secondary, tertiary.

23. Identify the isomer of C6H14 that only has primary and tertiary carbons. A) hexane B) 2,2-dimethylbutane C) 3-methylpentane D) 2,3-dimethylbutane Ans: D 24. Why can heats of combustion of constitutional isomers of hydrocarbons be used to measure their stabilities? I. Combustion of constitutional isomers gives different final states. II. Combustion of constitutional isomers gives the same final states. III. Constitutional isomers of hydrocarbons have the same potential energies. IV. Constitutional isomers of hydrocarbons have different potential energies. A) only I B) only II C) I and III D) II and IV Ans: D 25. The heats of combustion (-ΔH°) of heptane and 3,3-dimethypentane are 4,817 and 4,809 kJ/mol, respectively. Which statement is true? A) Heptane is 8 kJ/mol more stable then 3,3-dimethylpentane. B) 3,3-Dimethylpentane is 8 kJ/mol more stable than heptane. C) Stabilities cannot be compared since they are not isomers. D) Stabilities cannot be compared since they give different combustion products. Ans: B 26. The reaction of acetylene with hydrogen gas is shown below. Which statements are true concerning the reaction?

I. Acetylene is oxidized to ethane. II. Acetylene is reduced to ethane. III. Carbon changes oxidation state from -1 to -3. IV. Hydrogen (from H2) changes oxidation state from 0 to +1. A) I and III B) II and IV C) I, III, and IV D) II, III, and IV Ans: D

Page 5 Chem 341: Organic Chemistry, Prof. Sivaguru Jayaraman, Fall 2010.

Chapter 2 Hydrocarbon Frameworks – Alkanes: Answers

Prof. Sivaguru Jayaraman

27. How many methine groups are there in isopropylcyclopentane? A) one B) two C) three D) four Ans: B 28. What is the total number of constitutional isomers with the formula C5H12? A) two B) three C) four D) five Ans: B 29. What is the IUPAC name of the following?

A) 6-isopropyl-3-methylnonane B) 6-propyl-3-methylnonane Ans: A

C) D)

2-ethyl-5-isopropyloctane 2-ethyl-5-propyloctane

30. How many moles of O2 gas would be consumed in the complete combustion of 0.100 mole of C5H12? A) 0.100 mole...