210
Training Chem Set III
Organic Chemistry: Chem 210 Training Set III
The questions are arranged approximately in the order of the coverage of material in the lecture. This set covers the material of the third exam.
Notes: I. When listing reagents, a slash (/) is used between reagents that are employed simultaneously, and a semicolon (;) is used between reagents that are employed in a stepwise fashion. II. The stereochemistry conventions are illustrated below:
Br Br Br Br
OH
No stereochemistry shown
OH
Absolute stereochemistry shown
OH
Relative stereochemistry shown
OH
Absolute stereochemistry on one center, unspecified stereochemistry on the other
III. Abbreviations: Me = methyl, Et = ethyl, Pr = propyl, Bu = butyl, Pe = pentyl, Ph = phenyl (i.e. benzene as a substituent), AcO = acetate (H3CCOO), MCPBA = mchloroperbenzoic acid.
1. In the polar reaction of vinyl chloride with HBr the only product formed is 1,1bromochloroethane (not 1-bromo-2-chloroethane): ClCH=CH2 + HBr ClBrCHCH3 (not: ClCH2CH2Br)
What is the best explanation for this preference? The electrophile prefers to add to the chlorine-substituted carbon. Chlorine is causing steric hindrance for the addition of the bromine. The bromine electrophile is attracted to the lone electron pairs on chlorine. The two possible carbocations formed have the same stabilities, but 1,1bromochloroethane is much more stable than 1-bromo-2-chloroethane. e) The carbocation formed by protonation on the unsubstituted carbon is stabilized by resonance. f) A bromonium ion prevents attack on the carbon bearing the chlorine. a) b) c) d)
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Chem 210
Training Set III
2. The molecule of I-N3 adds to alkenes by an electrophilic mechanism similar to that of Br2. Taking into account the relative electronegativity of I (2.5) and N (3.0), and the fact that N3 is a stable anion, what is the most likely product of the following reaction?
I-N3
?
CH3
I a) H
N3 b) CH3
N3 H
I c) CH3 I
H
N3 d) CH3 N3
H
I
CH3
N3 e) I
H f) CH3 N3
I
H
CH3
3. Which of the compounds listed is the product of the following reaction?
4. Which of the following is not a redox reaction?
Page 2 of 16
Chem 210
Training Set III
5. When 4-penten-1-ol is treated with aqueous bromine, a cyclic bromo-substituted ether is formed rather than the expected bromohydrin. Select the explanation that best accounts for this result.
Br2 OH H 2O Br O
a) The ether is the result of a hydride shift in the initially formed carbocation. b) The ether is formed in the intramolecular nucleophilic attack on the initially formed bromonium ion. c) The reaction is initiated by the protonation of the system by the OH group. d) The ether is formed by a nucleophilic attack of the bond on the OH group. e) The initially formed bromonium ion undergoes an alkyl shift to form new C-O bond. f) Before any addition to the double bond, the OH group is replaced by Br. 6. We have discussed three ways to convert alkenes to alcohols: (A) acid-catalyzed hydration, (B) hydroboration-oxidation, and (C) oxymercuration-demercuration. Which of the following statements about these reactions is incorrect? a) B results in the syn stereochemistry of the -H and -OH groups, while A and C show no clear stereochemical preference. b) A and C give Markovnikov products, while B results in anti-Markovnikov regioselectivity. c) Carbocation rearrangements are observed for A, but unrearranged products are obtained from B and C. d) In all three reactions water serves as a nucleophile. e) In A a Brnsted acid is the electrophile, while in B and C Lewis acids play that role. f) B and C require consecutive additions of different reagents or catalysts, while in A only one reagent or catalyst is required. g) In B and C compounds of boron are involved, while in A no boron-derived chemicals are required. 7. Which product will result from the following reaction?
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Chem 210
Training Set III
8. What is the best description of the mechanism of the following transformation?
OH OH H
+
O
-H2O
OH2 OH OH
a)
H+ H2O
OH OH2
-H2O
OH
H O
O
OH O H
b)
H+ H2O
OH O
-HO-
O
H OH OH
OH2 -H2O O
c)
H+ H2O
HO
OH2
-H2O
O H2O
OH2 H OH OH H+ H2O OH OH2 OH2 H O O
d)
-H2O
O
9. Give the product of the following reaction.
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Chem 210
Training Set III
10. Which of the following will react with periodic acid (HIO4) to give an aldehyde product?
11. Compound A reacts with ozone (O3) to produce compounds I and II. What is the structure of compound A?
12. Compound B has a molecular formula of C6H12. It reacts with KMnO4to produce two identical ketones. It reacts with ozone (O3) to produce the same two products. What is the structure of compound B?
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Chem 210
Training Set III
13. Which of the following C11H16 hydrocarbons will not produce the carbonyl compounds shown below when treated with ozone?
C11H16
1) O3 2) Zn/AcOH + O O O
H O O
H + H2CO
a)
b)
c)
d)
e)
14. Which compound can most easily undergo elimination to give an alkyne?
15. Alkyne hydrogens are more acidic than alkene or alkane hydrogens because: a) The lone pair on alkyne carbon has higher s character. b) The anion formed is more stable. c) The electrons in the sp orbital are closer to the nucleus. d) All of the above. 16. Which reagents will give the following product?
a) H2/Pd/C
b) H2/Lindlar's catalyst
c) Li/NH3
d) H+/H2O
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Chem 210
Training Set III
17. Selected bond angles for five hydrocarbons are shown below. Arrange these hydrocarbons according to their pKa values, from the lowest to the highest. Assume that the structures of the corresponding conjugate bases are very similar to the hydrocarbons.
128o H H H H 109.5o H H H 115
o
H H H H H 108o H H 117o
180o H
H
A
B
C
D
E
a) E<B<D<C<A b) D<A<B<C<E c) B<D<A<E<C d) E<D<C<B<A
e) A<C<D<B<E f) E<C<B<A<D g) C<E<A<D<B h) A<B<C<D<E
18. Which reagents would be best to perform the following reaction?
a) BH3; NaOH/H2O2 c) NaNH2; CH3I; HgSO4/H2O/H2SO4
b) HgSO4/H2O/H2SO4 d) OsO4; HIO4
19. Which of the following synthetic schemes may be used to prepare the molecule shown below?
O
O
a) React acetylene with NaNH2/NH3; add half of an equivalent of 1,4dibromobutane; then add H2O/H2SO4/HgSO4 b) React acetylene with NaNH2/NH3; add one equivalent of 1,6-dibromohexane; then add BH3THF followed by OH/H2O2. c) React 1,6-octadiene with O3 followed by Zn/AcOH d) React 1,2-dimethylcyclohexene with KMnO4/H+ e) React cyclooctene with OsO4/pyridine; NaHSO3 followed by HIO4 f) Both (a) and (b) may work g) Both (a) and (d) may work h) Both (b) and (e) may work i) Both (c) and (e) may work
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Chem 210
Training Set III
20. What reagents (and in what sequence) would you use to carry out the following reaction?
several steps
a) (1) Cl2/h followed by KOH, (2) Br2/CCl4 followed by KOH b) (1) Br2/heat followed by KOH, (2) NBS/DMSO/H2O followed by KOH c) (1) KOH followed by Br2/heat, (2) Br2/CCl4 followed by KOH d) (1) KOH followed by Br2/H2O, (2) HBr followed by KOH e) (1) Cl2/h followed by NaOH, (2) HBr followed by KOH f) (1) Br2/H2O followed by NaOH, (2) Br2/H2O followed by NaOH g) (1) Br2/h followed by NaOH (2) OsO4/NaHSO3 followed by HBr 21-24. From the list below (a-j), select the appropriate reagent(s) for each step (21-24) of the following transformation: 21 Ph Br Ph 23 Br 22
Ph
Ph O a) PBr3 b) BH3THF followed by OH/H2O2 c) HgSO4/H2O/H2SO4 d) HBr/ether e) NaNH2/NH3 and PhCCH
Ph
24
Ph Ph
f) Br2/CCl4 g) NaNH2 h) H2/Lindlar's catalyst i) NaNH2/NH3 and PhCH2Br j) O3 followed by Zn/H+
25. Which of the reaction conditions would be best to perform the following reaction?
a) HBr (1 equivalent); Br2 c) Br2 (2 equivalents); H2/Pd/C
b) HBr (2 equivalents); Br2/h c) Br2 (2 equivalents); NaOH
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Chem 210
Training Set III
26-33. Each reaction requires a specific set of reagents and reaction conditions. Select the best set of reagents (a-j) for each transformation (26-33). You do not have to use all of the reagents, and you may use some of the reagents more than once. 26. Which reagent will yield a Markovnikov bromide when reacted with an alkene? 27. Which reagent needs to be used to convert a terminal alkyne to a ketone? 28. Which reagent needs to be used to convert a terminal alkyne to an aldehyde? 29. Which reagent will give a cis diol when reacted with a cyclic alkene? 30. Which is the best reagent to produce cis alkenes from alkynes? 31. Which reagent will give two molecules of organic product per each molecule of alkene reactant? 32. Which reagent will yield an halohydrin when reacted with an alkene? 33. Which reagent will yield an anti-Markovnikov alcohol when reacted with an alkene? a) BH3THF; H2O2/HO b) Hg(OAc)2/H2O; NaBH4 c) Lindlar catalyst/H2 d) O3; Zn/AcOH e) NBS/DMSO/H2O f) KOH g) OsO4/pyridine; NaHSO3 h) HgSO4/H2SO4/H2O i) NaNH2; CH3I j) HBr/ether
34. Which compound has the lowest wavelength of UV absorption (smallest max)?
35. Which of the following molecules will have a * transition in the 200-400 nm region?
a) H2C C CH2 b) c)
d)
e)
f)
36. Under thermodynamic control, which of the following products would predominate?
Page 9 of 16
Chem 210 37. A reaction under kinetic control depends on: a) The product stability (G). b) The activation energies (G). c) The relative energy of the reactants. d) All of the above.
Training Set III
38. Consider the addition of HBr to 1,3-butadiene. Which of the following statements about this reaction is incorrect? HBr + Br A B Br
a) A and B are formed from the same intermediate. b) In the intermediate, the positive charge on the secondary carbon is larger than the charge on the primary carbon, resulting in more rapid formation of A. c) In B the double bond is more stabilized by hyperconjugation than in A. d) At higher temperatures B is the major product. e) Under the kinetically controlled conditions A and B can easily interconvert. f) In the starting diene, the HOMO orbital lobes on the terminal carbons are larger than the corresponding lobes on the internal carbons. g) The first step of the reaction is controlled by the HOMO of the diene, while the second step is controlled by the LUMO of the intermediate. h) There is only one transition state leading to the intermediate, but two different transition states leading to the two products. i) All transition states resemble the intermediate more than they resemble starting diene or the products. 39. Which of the following best describes the MO diagram of the aromatic cycloheptratriene cation?
Page 10 of 16
Chem 210 40. Which of the following is antiaromatic?
Training Set III
41-42. Questions 41 and 42 concern the conjugated cyclic systems shown below (assume all molecules are planar):
A
B
C G
D
E
F c) C, G, F g) B, E, G d) C, D, F
41. Which compounds are aromatic? a) A, E, G b) B, C, G e) D, E, F f) A, D, F 42. Which compounds are antiaromatic? a) A, B, E, G b) A, B, C, G d) A, C, E, G e) B, D, E, G
c) D, E, F, G f) C, D, E, F
43. Compound A shows a large dipole moment. Which structure(s) should be used to adequately explain this observation?
+ _ A B _ + C
D
a) A
b) B
c) C
d) D
e) B and D
44. Which of the following resonance structures is not aromatic?
Page 11 of 16
Chem 210 45. What is the product of the following reaction?
Training Set III
46. Which of the following reaction is not a radical termination step?
47. Which is the least likely product of the following allylic bromination?
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Chem 210
Training Set III
48-51. Questions 48-51 involve use of the following sets of reagents. For each reaction shown, chose the reagent which would best be used to effect the transformation shown. a) PBr3/ether d) NBS/h/CCl4 48.
OH Cl
b) HBr/ether e) Br2/h
c) SOCl2/pyridine f) HCl/ether
g) Cl2/h
49.
HO
H
H
Br
50.
CH3 Br CH2 Br
51.
CH3
CH3 (major product)
52. Only one of the following reactions is likely to work as indicated. Which one?
Page 13 of 16
Chem 210
Training Set III
Selectivity of halogen radicals (per H) 3o 2 5 1600 97000 2o 1 3.5 80 1100 1o 1 1 1 1
F Cl Br I
Page 14 of 16
Chem 210
Training Set III
Page 15 of 16
Chem 210 Answer key: Set 3 1. E 2. C 3. A 4. A 5. B 6. D 7. D 8. A 9. D 10. B 11. A 12. A 13. D 14. D 15. D 16. B 17. D 18. C 19. G 20. A 21. F 22. G 23. I 24. C 25. A 26. J 53. 27. H 28. A 29. G 30. C 31. D 32. E 33. A 34. B 35. C 36. C 37. B 38. E 39. A 40. A 41. D 42. A 43. C 44. A 45. B 46. D 47. D 48. F 49. A 50. D 51. E 52. D
Training Set III
Page 16 of 16
Chem 210
Practice Exam 3A
Organic Chemistry: Chem 210
Practice Exam 3A
There are 28 questions on this exam. Check that you have done all of the problems and filled in the first 28 bubbles on the scantron. Most questions are worth 4 points; there are several two-point questions clearly labeled in the text. The maximum score on this exam is 100 points. Instructions Answer sheet 1) On the scantron, you need to clearly fill: your name and your student number, section number: (it is 001) test form (white = test form A; yellow = test form B). 2) Use a #2 pencil Exam policy 1) No electronic devices of any kind, such as calculators, cell phones, or even more advanced digital watches, are allowed. Possession of such devices during the exam, whether in use or not, is grounds for awarding a zero on the exam. 2) Molecular models are allowed (no instruction pages are permitted, however). 3) There are some blank pages at the end of the test that can be used as scratch paper. 4) Relevant tables, including the periodic table, are attached at the end of this exam. 5) Numerical values given in one question apply only to that question, and should not be used in other questions, unless there is a specific instruction to do so. If necessary, the values from the provided tables should be used, even if they differ from values that you may remember from different sources. 6) The exam results are based strictly on scantron's marks. No extraneous information is used to adjust the scores. Mark your choices with extra care. 7) Feel free to take this copy of the exam with you. The answer key will be posted on the web after the exam (under "News"). Hints 1) As you read the question, underline or circle key words to highlight them for yourself. 2) Questions have only one correct answer, unless indicated otherwise. No partial credit will be given. 3) There is no penalty for guessing.
Page 1 of 11
Chem 210
Practice Exam 3A
Notes: I. When listing reagents, a slash (/) is used between reagents that are employed simultaneously, and a semicolon (;) is used between reagents that are employed in a stepwise fashion. II. The stereochemistry conventions are illustrated below:
Br Br Br Br
OH
No stereochemistry shown
OH
Absolute stereochemistry shown
OH
Relative stereochemistry shown
OH
Absolute stereochemistry on one center, unspecified stereochemistry on the other
III. Abbreviations: Me = methyl, Et = ethyl, Pr = propyl, Bu = butyl, Pe = pentyl, Ph = phenyl (i.e. benzene as a substituent), AcO = acetate (H3CCOO), MCPBA = m-chloroperbenzoic acid.
******************************************************************************************** 1. (4 pts) Radicals can be compared according to their selectivity in hydrogen abstractions based on the reactivityselectivity principle. Which of the following radicals would be expected to have selectivity very similar to that of the H radical? a) Cl b) F c) HO d) Br e) I
2. (4 pts) Which of the following MO energy diagrams corresponds to the cyclopropenyl anion?
a)
b)
c)
d)
e)
3. (4 pts) Which of the following is the best characterization of the cyclopentadienyl cation?
a) antiaromatic
b) non-aromatic
c) carbocatatonic
d) aromatic
e) hyperconjugated
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Chem 210
Practice Exam 3A
4. (4 pts) Which of the following is (are) the product(s) of the reaction shown below?
Br2 H2O Br CH3 OH CH3 A B CH3 Br CH3 OH C CH3 Br OH CH3 D Br CH3 CH3 OH
a) A
b) B
c) C
d) D
e) A and B
f) C and D
5. (4 pts) How many stereoisomers of the product will form in this reaction?
1. OsO4 2. NaHSO3
a) 1 b) 2 c) 3 d) 4 e) 5
6. (4 pts) Which of the reagents shown below would accomplish the following transformations?
Br 1. A 2. B OH
A a) H3O b) NaOH c) HBr in ether d) NaNH2 e) H2/Pd/C
+
B BH3-THF;H2O2/NaOH BH3-THF;H2O2/NaOH Hg(OAc)2/H2O; NaBH4 Hg(OAc)2/H2O; NaBH4 NBS/DMSO/H2O
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Chem 210
Practice Exam 3A
7. (4 pts) Surprisingly, the reaction shown below goes through a bromonium ion. What is (are) the major product(s) of this reaction?
Br + HBr
A: B: C: D: a) A b) B c) C
trans-1,3-dibromocyclohexane cis-1,3-dibromocyclohexane trans-1,2-dibromocyclohexane cis-1,2-dibromocyclohexane e) A and B f) C and D g) A and C h) B and D
d) D
8-10. (2 pts each) Here is a retro-synthetic analysis for the preparation of propanal from 3-hexyne. What are the most appropriate reagents to accomplish each step of the synthesis of propanal?
8
9
HO
OH
10 H
O
propanal
a) Li/liquid NH3 e) Br2/AcOH; NaNH2 i) H2/Lindlar
b) BH3-THF; H2O2/NaOH f) O3; Zn/AcOH j) HIO4/THF/H2O
c) Hg(OAc)2/H2O; NaBH4 + g) KMnO4/H
d) OsO4;NaHSO3 + h) H3O
11. (4 pts) Which of the following compounds was the starting material for the oxidation shown below?
O ?
KMnO4/H+
HO O O OH
OH
+
CO2
a)
b)
c)
d)
Page 4 of 11
Chem 210
Practice Exam 3A
12. (4 pts) How is the following transformation best carried out?
O
O
a) BH3-THF; H2O2/NaOH d) OsO4; NaHSO3 b) H2SO4/H2O e) O3; Zn/AcOH c) HgSO4/H2SO4/H2O f) HIO4/H2O/THF
13. (4 pts) Carbocation A can be an intermediate in many reactions studied in Chem 210. Which of the following reactions does not involve A as an intermediate?
A
a) electrophilic addition of HBr to 2-butyne b) electrophilic addition of HCl to 1,2-butadiene c) electrophilic addition of HI to 1,3-butadiene d) rearrangement of 3-bromo-1-butene (the kinetic product) to 1-bromo-2-butene (the thermodynamic product) e) reaction of 3-hydroxy-1-butene with H2SO4 to yield 1,3-butadiene
14-16. (2 pts each) An unknown hydrocarbon A, with formula C6H12, reacts with 1 molar equivalent of H2 over a Pd catalyst. Hydrocarbon A also reacts with OsO4 to give a diol, B. When oxidized with KMnO4 in acidic solution, A gives 2 fragments. One fragment is propanoic acid, CH3CH2COOH, and the other is a ketone, C. From the structures (a)-(j) below, select the correct answers for questions 14-16. 14. What is the structure of A? 15. What is the structure of B? 16. What is the structure of C?
OH
OH
O H OH OH c) d) e)
a)
b)
O
OH O
OH
f)
g)
h)
i)
j)
Page 5 of 11
Chem 210
Practice Exam 3A
17. (4 pts) Consider the following synthesis. What is wrong with these transformations?
H2B BH3-THF BH2 H2O2, NaOH O
a) BH3 in THF is actually unreactive toward alkynes. b) BH3 should add to adjacent carbons, rather than the same carbon. c) The oxygen in THF is responsible for oxidation; H2O2 and NaOH are not required. d) Borane can be used as an electrophile only with non-terminal alkynes. e) The borane addition follows regiochemistry opposite to that shown. 18. (4 pts) All six MOs of benzene are shown below in a random order, in a view from the top (i.e. only top lobes of p orbitals on carbon atoms are visible). Which of the following electronic transitions will correspond to the absorption band with the smallest max?
A
B
C
D
E
F
a)
E
F
b) A
B
c)
E
B
d) C
F
e)
C
B
19. (4 pts) What is the absolute configuration of the stereogenic centers in the product(s) of the following reaction?
CH3 H + Br2 1,2-dibromo-3-methylcyclohexane
a) 1R, 2R, 3R f) 1S, 2R, 3R
b) 1S, 2S, 3S g) 1S, 2S, 3R
c) 1R, 2S, 3R d) 1R, 2R, 3S h) 1R, 2R, 3R and 1S, 2S, 3R
e) 1R, 2S, 3S i) 1R, 2S, 3R and 1S, 2R, 3R
20. (4 pts) In which of the following solvents is it possible to create acetylide anions? a) AcOH b) H2O c) H3COH d) (i-Pr)2NH e) (H3C)2CO
21. (4 pts) (R)-2-fluorobutane undergoes free-radical chlorination with Cl2. Including stereoisomers, how many monochlorinated substitution products will form? a) 3 b) 4 c) 5 d) 6 e) 7 f) 8
Page 6 of 11
Chem 210
Practice Exam 3A
22. (4 pts) The following transformation is carried out in three steps. What are the appropriate reagents for the first (I) step?
H
I
II
H III HO
OH H
a) H2/Lindlar catalyst b) NaNH2/NH3 (liquid); CH3CH2Br c) O3; Zn/AcOH d) KMnO4/NaOH
e) HCCH/NaNH2/THF/CH3I f) H2/Pd/C g) Li/NH3 (liquid) h) NBS/DMSO/H2O
23. (4 pts) Consider the following transformation in which a cyclic bromoether is formed, rather than the expected bromohydrin. Which of the electron-pushing scheme best represents the mechanism of this reaction?
O OH Br2, H2O -HBr Br
?
a) Br H O
b) Br
c) Br
d) H
H O
Br
e) Br
O H
O H H
O
24. (4 pts) Assuming that only monosubstitution products are formed in the reaction shown below, what would be the expected ratio of 2o to 3o chlorides?
Cl2 h
a) 3/1 b) 6/7 c) 3/2 d) 21/10 e) 15/17
25. (4 pts) In the molecule shown below selected C-H bonds are labeled with capital letters. Arrange these bonds according to the difficulty with which they would be broken in radical-forming reactions, starting with the strongest.
H H D H A H C CH3 H B
H
a) e)
B>D>A>C D>B>A>C
b) D > A > C > B f) C > B > A > D
c) A > D > C > B g) A > C > B > D
d) B > C > A > D h) C > A > D > B
Page 7 of 11
Chem 210
Practice Exam 3A
26. (4 pts) What is(are) the product(s) of the following reaction?
NBS h, CCl4
OH Br Br OH Br A B C D Br
a) A
b) B
c) C
d) D
e) A and B
f) C and D
27. (4 pts) Consider only the following two major products of the addition reaction shown below. Which statement is true about this reaction?
Br + HBr +
Br
a) The major product formed under thermodynamic control is 4-bromo-4-methyl-2-pentene. b) The major product formed under kinetic control is 4-bromo-2-methyl-2-pentene. c) The major product formed under thermodynamic control is 4-bromo-2-methyl-2-pentene. d) The 1,2 product is kinetically controlled, and the 1,4 product is thermodynamically controlled. e) There is no thermodynamic or kinetic control in this reaction.
28. (4 pts) On reaction with acid, 4-pyrone is protonated to give a very stable cationic product. Which of the following structures shows the protonation site in that product?
O 4-pyrone O H d)
a)
O H H O
b)
O
c)
O
O
e)
O
H
O
H H
O
O H
O
Page 8 of 11
Chem 210
Practice Exam 3A
Selectivity of halogen radicals (per H) 3o 2 5 1600 97000 2o 1 3.5 80 1100 1o 1 1 1 1
F Cl Br I
Page 9 of 11
Chem 210
Practice Exam 3A
Page 10 of 11
Chem 210
Practice Exam 3A
Answer Key: 3A 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. A C A F B D C A D J B C A C D F E B H D D B B D A F C C
Page 11 of 11
Chem 210
Practice Exam 3B
Organic Chemistry: Chem 210 Practice Exam 3B
There are 28 questions on this exam. Check that you have done all of the problems and filled in the first 28 bubbles on the scantron. Most questions are worth 4 points; there are several two-point questions clearly labeled in the text. The maximum score on this exam is 100 points. Instructions Answer sheet 1) On the scantron, you need to clearly fill: your name and your student number, section number: (it is 001) test form (white = test form A; yellow = test form B). 2) Use a #2 pencil Exam policy 1) No electronic devices of any kind, such as calculators, cell phones, or even more advanced digital watches, are allowed. Possession of such devices during the exam, whether in use or not, is grounds for awarding a zero on the exam. 2) Molecular models are allowed (no instruction pages are permitted, however). 3) There are some blank pages at the end of the test that can be used as scratch paper. 4) Relevant tables, including the periodic table, are attached at the end of this exam. 5) Numerical values given in one question apply only to that question, and should not be used in other questions, unless there is a specific instruction to do so. If necessary, the values from the provided tables should be used, even if they differ from values that you may remember from different sources. 6) The exam results are based strictly on scantron's marks. No extraneous information is used to adjust the scores. Mark your choices with extra care. 7) Feel free to take this copy of the exam with you. The answer key will be posted on the web after the exam (under "News"). Hints 1) As you read the question, underline or circle key words to highlight them for yourself. 2) Questions have only one correct answer, unless indicated otherwise. No partial credit will be given. 3) There is no penalty for guessing.
Page 1 of 12
Chem 210
Practice Exam 3B
Notes: I. When listing reagents, a slash (/) is used between reagents that are employed simultaneously, and a semicolon (;) is used between reagents that are employed in a stepwise fashion. II. The stereochemistry conventions are illustrated below:
Br Br Br Br
OH
No stereochemistry shown
OH
Absolute stereochemistry shown
OH
Relative stereochemistry shown
OH
Absolute stereochemistry on one center, unspecified stereochemistry on the other
III. Abbreviations: Me = methyl, Et = ethyl, Pr = propyl, Bu = butyl, Pe = pentyl, Ph = phenyl (i.e. benzene as a substituent), AcO = acetate (H3CCOO), MCPBA = m-chloroperbenzoic acid.
************************************************************************************** 1 - 2. Radicals can be compared according to their selectivity in hydrogen abstraction reactions based on the reactivity-selectivity principle. Compare the following carbon-centered radicals: a) HCC 1. 2. 3. b) H3C c) Ph d) NC e) H2C=CHCH2
(4 pts) Which of the above radicals would be expected to be the most selective? (4 pts) Which of the above radicals would be expected to be the least selective?
(4 pts) Which of the following MO energy diagrams corresponds to the cyclobutadienyl dication?
a)
4.
b)
c)
d)
e)
(4 pts) How many stereoisomers of the product will form in this reaction?
H2 Pd/C
a) 1
b) 2
c) 3
d) 4
e) 8
Page 2 of 12
Chem 210
5.
Practice Exam 3B
(4 pts) The following transformation is carried out in three steps (I - III). What are the appropriate reagents for the first (I) step?
I
II
III O
a) b) c) d) 6.
Br2/H2O NaNH2/THF NBS/CCl4 Br2/CCl4
e) f) g) h)
HgSO4/H2SO4/H2O BH3THF; H2O2/NaOH Hg(OAc)2/H2O; NaBH4 KMnO4/NaOH
(4 pts) Which of the compounds listed below is a product of the following reaction?
CH3
NBS DMSO, H2O
OH CH3 H Br CH3 OH H OH CH3 Br Br H Br CH3 OH H
a)
CH3 OH H Br Br CH3 H OH
b)
c)
d)
e)
f)
7.
(4 pts) (R)-2-fluorobutane undergoes free-radical fluorination with F2. Including stereoisomers, how many products containing two fluorine atoms will form in this reaction? a) 3 b) 4 c) 5 d) 6 e) 7 f) 8
8.
(4 pts) Which of the following molecules are aromatic?
A
B
C
D
E
a) A, B, E
b) B, C, D
c) C, D, E
d) B, D, E
e) A, B, D, E
Page 3 of 12
Chem Exam 210
9-11.
Practice 3B
For questions 9 - 11 consider the retrosynthetic analysis for the target aldehyde shown below:
H O
9.
?
(4 pts) Based on the reactions covered in Chem 210, which of the following structures is not an immediate precursor to the target molecule?
OH H OH A
a) A b) B
B
c) C
C
d) D
D
e) E
E
10. (2 pts) Which of the following pairings of a synthetic precursor (see above) with reagents will yield the target compound? a) A reacted with KMnO4/H+ c) C reacted with HIO4/THF/H2O e) E reacted with KMnO4/H+ b) B reacted with Hg(OAc)2/H2O; NaBH4 d) D reacted with HgSO4/H2SO4/H2O f) E reacted with Hg(OAc)2/H2O; NaBH4
11. (4 pts) If the starting materials are limited to acetylene (HCCH) and compounds containing only one carbon, which precursor (see above) will be the part of the shortest (fewest steps) synthesis? a) A 12. b) B c) C d) D e) E
(4 pts) Consider the following reaction of 1-methylcyclohexene with NBS. Four likely products of this reaction are shown below. One of the likely products is not shown, however.
Br NBS CCl4 + Br + + Br Br +
?
Which of the following is the "missing" product of that reaction?
a) Br b) Br c) Br Br Br Br d) e)
Page 4 of 12
Chem 210
13.
Practice Exam 3B
(4 pts) When reacted with an alkene, which of the following reagents would not introduce at least one -OH group into the final product? a) Hg(OAc)2/H2O; NaBH4 d) KMnO4/NaOH b) BH3THF; H2O2/NaOH e) HIO4/H2O/THF c) OsO4; NaHSO3 f) NBS/H2O/DMSO
14.
(4 pts) A schematic representation of -type molecular orbitals for 3-methylene-1,4-pentadiene is shown below. The orbitals are arranged in random order. Which of the following electronic transitions will correspond to the absorption band with the smallest max?
A
B
C
D
E
F
a) A 15.
F
b) B
A
c) B
E
d) C
D
e) C
F
(4 pts) Which starting material should be used to produce the compound shown below?
H O
O
?
a)
1. O3 2. Zn/AcOH
H O O
b)
c)
d)
e)
16.
(4 pts) What is the best way to carry out the following transformation?
H O H
a) KMnO4/ H3O+ d) BH3; NaOH/H2O2
b) HgSO4/H2SO4/H2O e) Hg(OAc)2/H2O; NaBH4
c) H2/Lindlar; O3; Zn/H3O+ f) HIO4/H2O
Page 5 of 12
Chem 210
17.
Practice Exam 3B
(4 pts) Which is the least likely protonation site in the conjugated alkene shown below?
4 5 3 2 1 6
a) 1 18.
b) 2
c) 3
d) 4
e) 5
f) 6
(4 pts) Compound X shows a single UV absorption at 226 nm, and it can be catalytically hydrogenated to yield 2,6-dimethyloctane. On ozonolysis followed by treatment with zinc and acetic acid, compound X yields formaldehyde (H2CO), acetone ((CH3)2CO), and the dialdehyde shown below. What is the structure of compound X?
O O O CH
HCCH2CH2C
(dialdehyde) a) b)
c)
d)
e)
19.
(4 pts) Which of the following statements best explains why 1-propyne can be deprotonated by the ethyl anion (CH3CH2)? a) b) c) d) e) the acetylide anion is a stronger base than the ethyl anion ethane has a lower pKa than acetylene the lone-pair orbitals in acetylide anions have more s character than those in alkyl anions the acetylide anion is a weaker base than an alkyl anion the lone-pair orbitals in acetylide anions have more p character than those in alkyl anions
20.
(4 pts) What is the most likely product of the following reaction?
CHCH3 H2SO4 H2O
a)
CH2CH3
b)
CH2CH3 OH
c) CH2CH2OH
d)
OH
e)
OH
OH
Page 6 of 12
Chem 210
21.
Practice Exam 3B
(4 pts) Which of the following mechanisms is the most likely reaction path for the transformation shown below?
H Br2 H2O O Br
a)
Br-Br H Br H -H O H Br H O Br
H
O
H
b)
OH2 H H H
-H
O
OH H Br
O Br
Br
c)
Br--Br H Br H H O H
-H
OH H Br
O Br
d)
Br H2O H H O Br Br Br H Br -H Br O H Br O Br
Page 7 of 12
Chem 210
22.
Practice Exam 3B
(4 pts) Assuming that only monochlorides are products in the reaction shown below, what would be the expected ratio of the two alkyl chlorides formed in that reaction?
Cl2 hv
a) 1/6 23. b) 1/4 c) 1/2 d) 3/5 e) 5/6
(4 pts) Which of the sets of reagents shown below would accomplish the following transformation?
Br
1. A 2. B B
OH
A
a) b) c) d) e) BH3THF; H2O2/NaOH H2/Pd/C H3PO4 KOH NaOH
H2SO4 BH3THF; H2O2/NaOH Hg(OAc)2/H2O; NaBH4 Hg(OAc)2/H2O; NaBH4 BH3THF; H2O2/NaOH
24 - 25. Consider the following electrophilic addition of HCl to 2-methyl-1,3-cyclohexadiene.
Cl 1 eq HCl ether, low temperature A B C D Cl Cl Cl
24. (2 pts) Which of the above chlorides is not going to form in this reaction? a) A b) B c) C d) D e) all of them (A-D) are products of the addition
25. (2 pts) Which of the above chlorides is expected to be the major product under the conditions specified? a) A b) B c) C d) D
Page 8 of 12
Chem 210
Practice Exam 3B
26 - 28. Iodine azide, IN3, adds to 1-methylcyclohexene by an ionic two-step mechanism similar to those discussed in our class for other electrophiles. Only the products shown below form in that reaction.
CH3 N3 CH3 H I + CH3 N3 I H
IN3
26. (2 pts) What is the first intermediate formed in that reaction? a) a teriary carbocation b) iodonium ion c) azidonium ion d) an allylic carbocation
27. (2 pts) What is the stereochemistry of the addition? a) syn b) anti c) syn/anti (50:50) d) cannot be determined
28. (2 pts) What is the nucleophile in the second step? a) N3 b) I c) H d) iodonium ion
================================================================================== End of the exam
Page 9 of 12
Chem 210
Practice Exam 3B
Selectivity of halogen radicals (per H) F Cl Br I 3o 2 5 1600 97000 2o 1 3.5 80 1100 1o 1 1 1 1
Page 10 of 12
Chem 210
Practice Exam 3B
Page 11 of 12
Chem 210
Answer key: 3 B 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. E D B A D B C D B C D E E D B C A C C A A E D B A B B A
Practice Exam 3B
Page 12 of 12
Chem 210
Practice Exam 3C
Organic Chemistry: Chem 210
Practice Exam 3C There are 30 questions on this exam. Check that you have done all of the problems and filled in the first 30 bubbles on the scantron. Most questions are worth 4 points; there are several two-point questions clearly labeled in the text. The maximum score on this exam is 100 points. Instructions Answer sheet 1) On the scantron, you need to clearly fill: your name and your student number, section number: (it is 001) test form (white = test form A; yellow = test form B). 2) Use a #2 pencil Exam policy 1) No electronic devices of any kind, such as calculators, cell phones, or even more advanced digital watches, are allowed. Possession of such devices during the exam, whether in use or not, is grounds for awarding a zero on the exam. 2) Molecular models are allowed (no instruction pages are permitted, however). 3) There are some blank pages at the end of the test that can be used as scratch paper. 4) Relevant tables, including the periodic table, are attached at the end of this exam. 5) Numerical values given in one question apply only to that question, and should not be used in other questions, unless there is a specific instruction to do so. If necessary, the values from the provided tables should be used, even if they differ from values that you may remember from different sources. 6) The exam results are based strictly on scantron's marks. No extraneous information is used to adjust the scores. Mark your choices with extra care. 7) Feel free to take this copy of the exam with you. The answer key will be posted on the web after the exam (under "News"). Hints 1) As you read the question, underline or circle key words to highlight them for yourself. 2) Questions have only one correct answer, unless indicated otherwise. No partial credit will be given. 3) There is no penalty for guessing.
Page 1 of 12
Chem 210
Practice Exam 3C
Notes: I. When listing reagents, a slash (/) is used between reagents that are employed simultaneously, and a semicolon (;) is used between reagents that are employed in a stepwise fashion. II. The stereochemistry conventions are illustrated below:
Br Br Br OH
Relative stereochemistry shown
Br
OH
No stereochemistry shown
OH
Absolute stereochemistry shown
OH
Absolute stereochemistry on one center, unspecified stereochemistry on the other
III. Abbreviations: Me = methyl, Et = ethyl, Pr = propyl, Bu = butyl, Pe = pentyl, Ph = phenyl (i.e. benzene as a substituent), AcO = acetate (H3CCOO), MCPBA = m-chloroperbenzoic acid. ************************************************************************************* 1. (4 pts) The following transformation is carried out in three steps (I - III). If the second step involves hydrogenation, what are the appropriate reagents for the first (I) step?
Br I II III HO OH OH OH
a) Br2/H2O c) H2SO4/H2O e) NaNH2/THF g) BH3THF; H2O2/NaOH
b) H2/Lindlar d) Hg(OAc)2/H2O; NaBH4 f) O3; Zn/AcOH h) KMnO4/OH
2. (4 pts) How many diols, including stereoisomers, are formed, in the following reaction?
Hg(OAc)2 (excess) H2O
a) 1 b) 2 c) 3 d) 4
NaBH4
e) 6
3. (4 pts) 2-Butyne is allowed to react with Li in NH3(liq). The obtained product is treated with Br2 in CCl4. Which of the following compounds is the end result of this sequence of reactions?
a) H H Br CH3 CH3 H H3C
b) Br H CH3 H3C H
c) Br H CH3 H3C H
d) Br H H Br H3C H3C
e) Br H H Br
Br
Br
Br
Page 2 of 12
Chem 210
4 5. Assume that only monochlorides are produced in the following reaction.
Practice Exam 3C
Cl2 light
4. (2 pts) Which chloride will be produced in the highest yield? a) b) c) d) 1-chloro-2-methylbutane 2-chloro-2-methylbutane 2-chloro-3-methylbutane 1-chloro-3-methylbutane
5. (2 pts) What fraction of the total would 2o chlorides be? a) 1/6 b) 7/9 c) 5/9 d) 5/21 e) 1/3
6. (4 pts.) Which of the following MO diagrams would best represent planar cyclooctatetraene?
a)
b)
c)
d)
e)
Page 3 of 12
Chem 210
7. (4 pts) How many stereoisomers of the product will form in this reaction?
Practice Exam 3C
CH3 O excess H2 Pd/C H2C C CH3
a) 1 b) 2 c) 3 d) 4 e) 6
?
H
8. (4 pts.) Assuming that all non-hydrogen atoms in the planar molecules shown below are sp2 hybridized, which molecules are antiaromatic?
O N
A
S N N
B
N N O N N
C
c) C d) D
S
D
e) D and E
E
a) A
b) B
9. (4 pts) Which of the following compounds is among the major products of the following reaction?
CH3 H
1. BH3/THF 2. H2O2, OH
?
a) CH3 OH OH H
b) CH3 H H OH
c) CH3 OH H H
d) H OH H CH3
e) CH3 H BH2 H
Page 4 of 12
Chem 210
Practice Exam 3C
10. (4 pts) Which of the following statements about electronic transitions in organic molecules is incorrect? a) Usually, n * transitions are of low intensity because the orbitals involved are perpendicular. b) Electronic transitions occur when incoming photons have energy that matches the energy gap between the orbitals involved. c) Absorption of UV or visible light generates a molecule in its excited electronic state. d) More conjugated systems have shorter max values than less conjugated systems. e) HOMO LUMO transitions are of the lowest energy relative to other electronic transitions in the same molecule. 11. (4 pts) What is the most likely product of the following reaction?
KMnO4 H+
?
a)
O OH O H O
b)
O OH O
c)
O OH O
d)
O H OH O
e)
O
12. (4 pts) Which set of reagents (in the correct order) would accomplish the following transformation?
CH3CH2CH2
H
I
II
CH3CH2CH2 H
CH3 H
I a) b) c) d) e) NaNH2/NH3(l); CH3I, KOH/THF; CH3I H2/Lindlar catalyst BH3-THF; H2O2/NaOH NaNH2/THF; CH3CH2I
II H2/Lindlar catalyst H2/Pd/C NaNH2/THF; CH3I H2SO4 H2/Lindlar
Page 5 of 12
Chem 210
Practice Exam 3C
13. (4 pts) A reaction of propyne with Hg2+ is run in methanol (CH3OH) in the absence of water, but in the presence of a strong acid (H+) with a non-nucleophilic counterion. If this reaction follows a typical mechanism of electrophilic addition, what would be the expected product?
a) O OCH3
b) OCH3 OCH3 CH3O
c) OCH3
d) OCH3 O
e) OCH3 OCH3
14. (4 pts.) Which of the following reactions would not yield at least one ketone? a) ozonolysis (followed by reductive workup with Zn/H+) of mono-substituted alkene b) oxidative cleavage of a trisubstituted cyclic alkene c) oxymercuration/demercuration of terminal alkyne d) hydroboration of an internal alkyne, followed by H2O2/NaOH e) periodate oxidation of a tertiary 1,2-diol 15. (4 pts) If the molecule shown below is treated with ozone followed by zinc and acetic acid, what are the products formed?
O a) H
O
O H O O H H H
O
O O H H O H H O H O H O O O H O H O H CO2
O
O
b)
H O O O O
O H H O
O
c)
H O O H H O O O O O H H O O O H
CO2
d)
e)
H
Page 6 of 12
Chem 210
Practice Exam 3C
16. (4 pts) In the vinyl cation the positively-charged carbon is sp hybridized. Which statement about the hybridization type of the negatively-charged carbon in the vinyl carbanion is correct? a) The carbon is sp hybridized to help to stabilize the orbital with the lone pair. b) The carbon is sp hybridized to minimize repulsion between the bonding and nonbonding electrons. c) The carbon is sp2 hybridized to maximize s character in the orbital with the lone pair. d) The carbon is sp2 hybridized to minimize angle strain around the bond. e) The carbon is sp3 hybridized to maximize separation between all electrons. f) The carbon is sp3 hybridized to avoid antiaromaticity that would be present if it were planar. 17. (4 pts) Which of the molecules listed below can be synthesized from propyne using only one of the reactions discussed in Chem 210?
Br Br
Br Br
Br
Br
O H
O
A
a) A and B b) C and D
B
C
c) A, B, and D
D
d) B, C, and D e) all
18-19. Radicals listed below are allowed to abstract hydrogen atoms from propane. a) Cl b) H3C c) H d) HO e) H3CS
18. (2 pts) Which radical will generate the largest ratio of 2-propyl to 1-propyl radicals? 19. (2 pts) Which radical will be least selective? 20-21. Fluorocyclohexane undergoes free-radical fluorination with F2. Consider only products containing two fluorine atoms. 20. (2 pts) How many constitutional isomers with two fluorines are present? a) 1 b) 2 c) 3 d) 4 e) 5 f) 6
21. (2 pts) How many meso compounds with two fluorines are present? a) 1 b) 2 c) 3 d) 4 e) 5 f) 6
Page 7 of 12
Chem 210
Practice Exam 3C
22-25. Some of the possible products of electrophilic addition of HCl to 1-phenyl-1,3butadiene are shown below (Z-isomers have been omitted). A B
Cl Cl HCl Cl Cl
Cl
C
Cl
D E 22. (2 pts) Which of the above chlorides is not likely to form at all?
a) A b) B c) C d) D e) E f) F
F
23. (2 pts) Which of the above chlorides is expected to be the major product under thermodynamic control? a) A b) B c) C d) D e) E f) F
24. (2 pts) Which products are 1,4 adducts? a) A and F b) B and E c) B and F d) C and F e) D and E
25. (2 pts) Which 1,2-adduct would be produced in the largest quantities under thermodynamic control? a) A b) B c) C d) D e) E f) F
26. (4 pts) Which of the following is not the product of a radical chain-reaction of 2-pentene with NBS?
Br Br Br a) b) c) d) Br
Page 8 of 12
Chem 210
27. (4 pts) Which is the most likely protonation site in the conjugated alkene shown below?
1 2 5 3 4
Practice Exam 3C
a) 1
b) 2
c) 3
d) 4
e) 5
28- 30 For questions 28-30 consider the retrosynthetic analysis for the target ketone shown below:
O
?
O HO OH
A
B
C
D
E
28. (4 pts) Based on the reactions covered so far in Chem 210, which of the following structures is not an immediate precursor to the target molecule? a) A b) B c) C d) D e) E
29. (4 pts) Which of the following pairings of a synthetic precursor (see above) with reagents will yield the target compound? a) A reacted with KMnO4/H+ c) C reacted with O3; Zn/AcOH e) E reacted with KMnO4/NaOH b) B reacted with H2SO4/H2O d) D reacted with H2/Lindlar catalyst
30. (4 pts) If the starting materials are limited to building blocks containing no more than 2 carbons, which precursor (see above) will be part of the shortest (fewest steps) synthesis? a) A b) B c) C d) D e) E
=========================================================================== End of the exam
Page 9 of 12
Chem 210
Practice Exam 3C
Selectivity of halogen radicals (per H) 3o 2 5 1600 97000 2o 1 3.5 80 1100 1o 1 1 1 1
F Cl Br I
Page 10 of 12
Chem 210
Practice Exam 3C
Page 11 of 12
Chem 210
Answer key: 3C 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. E C C C (2 pts) E (2 pts) A B D D D A A C A E C E E (2 pts) D (2 pts) D (2 pts) B (2 pts) D (2 pts) F (2 pts) B (2 pts) F (2 pts) B A A C B
Practice Exam 3C
Page 12 of 12
Chemistry 210 Exam III November 12, 2007 Form A There are 30 questions on this exam. Check that you have done all of the problems and filled in the first 30 bubbles on the scantron. Most questions are worth 4 points; there are a couple of two-point questions clearly labeled in the text. The maximum score on this exam is 100 points. Instructions Answer sheet 1) On the scantron, you need to clearly fill: your name and your student number, section number: (12:20 class is section 001, 3:25 class is section 002) test form (white = test form A; yellow = test form B). 2) Use a #2 pencil Exam policy 1) No electronic devices of any kind, such as calculators, cell phones, or even more advanced digital watches, are allowed. Possession of such devices during the exam, whether in use or not, is grounds for awarding a zero on the exam. 2) Molecular models are allowed (no instruction pages are permitted, however). 3) There are some blank pages at the end of the test that can be used as scratch paper. 4) Relevant tables, including the periodic table, are attached at the end of this exam. 5) Numerical values given in one question apply only to that question, and should not be used in other questions, unless there is a specific instruction to do so. If necessary, the values from the provided tables should be used, even if they differ from values that you may remember from different sources. 6) The exam results are based strictly on scantron's marks. No extraneous information is used to adjust the scores. Mark your choices with extra care. 7) Feel free to take this copy of the exam with you. The answer key will be posted on the web after the exam (under "News"). Hints 1) As you read the question, underline or circle key words to highlight them for yourself. 2) Questions have only one correct answer, unless indicated otherwise. No partial credit will be given. 3) There is no penalty for guessing.
1
Notes: I. The stereochemistry conventions are illustrated below:
Br Br Br Br
OH
No stereochemistry shown (all stereoisomers possible)
OH
Absolute stereochemistry shown
OH
Relative stereochemistry shown
OH
Absolute stereochemistry on one center, unspecified stereochemistry on the other
II. Abbreviations: Me = methyl, Et = ethyl, Pr = propyl, Bu = butyl, Pe = pentyl, Ph = phenyl (i.e. benzene as a substituent), AcO = acetate (H3CCOO), MCPBA = m-chloroperoxybenzoic acid III. When listing reagents, a slash (/) is used between reagents that are employed simultaneously, and a semicolon (;) is used between reagents that are employed in a stepwise fashion. ************************************************************************************* 1. (4 pts.) Consider the cyclic ion shown below. Which statement about A is correct?
H H A: H H H
a) A is aromatic b) A is antiaromatic c) A can be made aromatic by proton abstraction d) A can be made aromatic by hydride abstraction e) A can be made aromatic by adding two electrons 2. (4 pts) How would you prepare the epoxide shown below?
O
a) b) c) d) e)
treat 2Z-butene with NBS/H2O/DMSO followed by H+/H2O treat 2Z-butene with MCPBA in CH2Cl2 treat 2E-butene with Br2/H2O; followed by NaOH/H2O treat 2E-butene with NMO and catalytic OsO4 treat 1-butene with Cl2/H2O followed by KOH/CH3CH2OH
3. (4 pts) The MO's of 1,3,5-hexatriene are shown schematically below in a random order. Which of the following transitions will have the shortest max?
A
a) A F b) B
B
C c) F
C
C
D
d) C D
E
e) B F
F
2
4 5. Assume that only monochlorides, C7H15Cl, are produced in the radical-chain chlorination of 2,4dimethylpentane.. 4. (2 pts) What is the structure of the chloride that is produced in the highest yield in that reaction?
Cl Cl Cl c) Cl Cl
a)
b)
d)
e)
5. (2 pts) What fraction of the total monochlorides would be primary chlorides? a) 2/17 b) 10/29 c) 6/11 d) 12/29 e) 6/7
6. (4 pts) How many diols, including stereoisomers, are formed in the following reaction?
H3 C C C CH3 1. H 2 /Lindlar catalyst 2.OsO4 3.Na 2SO3 /H2 O
a) 1
b) 2
c) 3
d) 4
e) 5
7. (4 pts) Methyl vinyl ether, H2C=CH-OCH3, reacts with Br2/CH3OH. If methanol reacts as water would, and if this reaction follows a typical mechanism of electrophilic addition, what would be the expected product?
Br H3CO a) b) OCH3 Br OCH3 OCH3 OCH3 Br OCH3 c) Br O OCH3 d) e) H3CO O OCH3
8. (2 pts) Based on the reactivity-selectivity rule, which radical will show selectivity in hydrogen abstractions that is most similar to the selectivity shown by the allyl radical in the same reaction? a) Ph b) PhCH2 c) (CH3)3C d) H e) H3C
3
9. (4 pts) A mixture of alkenes was treated with BH3-THF to yield the following trialkylborane as one of several products.
B
Based on this observation, which of the following alkenes could not have participated in the formation of the trialkylborane shown above?
a)
b)
c)
d)
e)
10. (4 pts.) Which of the following reactions would not yield at least one aldehyde? a) periodate (HIO4) oxidation of a secondary 1,2-diol b) oxidative cleavage with O3; Zn/H+ of unsubstituted cyclic alkene c) oxymercuration/demercuration of terminal alkyne d) hydroboration of a terminal alkyne, followed by H2O2/NaOH e) ozonolysis (followed by reductive workup with Zn/H+) of mono-substituted alkene
11. (4 pts) What is the product of the following reaction?
1. BH 3 /THF 2. H2 O2 /HO PBr3 HC C ?
O
OH
a)
b)
c)
d)
e)
12. (2 pts) Based on the reactivity-selectivity principle, which is the correct order of hydrogenabstraction selectivities for allylic, benzylic and vinylic radicals, starting with the most selective? a) allylic > benzylic > vinylic c) benzylic > allylic > vinylic e) vinylic > allylic > benzylic b) allylic > vinylic > benzylic d) benzylic > vinylic > allylic f) vinylic > benzylic > allylic
4
13. (4 pts) For the hydrocarbons shown below with some of their HCH bond angles the structures of the corresponding conjugate bases are very similar to those of the hydrocarbons themselves. Selecting the most acidic hydrogens for each compound, what is the correct order of pKa's for these hydrocarbons?
128 o 118 o H 115 o H H A B H C H H H H H H 108 o
a) A > B > C d) B > C > A
b) A > C > B e) C > A > B
c) B > A > C f) C > B > A
14 16. Consider the retrosynthetic analysis for the target aldehyde shown below:
H O
?
HO OH O A B C D E H
14. (2 pts) Based on the reactions covered so far in Chem 210, which of the following structures is not an immediate precursor to the target molecule? a) A b) B c) C d) D e) E
15. (2 pts) Which of the following pairings of a synthetic precursor (see above) with reagents will not yield the target molecule? a) b) c) d) A B C D reacted with BH3-THF followed by H2O2/NaOH reacted with ozone followed by Zn/AcOH reacted with KMnO4/H+ reacted with H2 and Pd/C
16. (2 pts) Which of the synthetic precursors (see above) can be converted into the target molecule by reduction? a) A b) B c) C d) D e) E
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17. (4 pts) Which of the molecules listed below cannot be synthesized from propyne using only one of the reactions discussed in Chem 210? Using the same reaction repeatedly, or using reagents in excess is considered as "one" reaction.
OH O a) O b)
H
Br
Br O c) d)
OH
O
e)
18-19. A Chem 210 student produced the following aldehyde from 2-butyne in three steps, despite the fact that a two-step transformation could have achieved the same result.
I II III O H
18. (4 pts) Most likely, what was the reaction this student used in the third (III) step? a) hydroboration followed by basic hydrogen peroxide b) oxidative cleavage with acidic potassium permanaganate (KMnO4/H+) c) oxymercuration with Hg(OAc)2 followed by NaBH4 d) hydroxylation with basic potassium permanganate(KMnO4/HO) e) oxidative cleavage with HIO4 in THF 19. (2 pts) Which of the following reagents would have to be used in a two-step synthesis? a) H3O+/H2O b) MCPBA c) KMnO4/H+ d) O3; Zn/H+ e) NBS/h
20. (4 pts) Which of the structures below is the best (as accurate as possible) representation of the stereochemical outcome of the addition of Br2 to 2Z-butene?
Br Br Br Br Br
Br a)
Br b)
Br c)
Br d)
Br e)
21. (4 pts) Which of the marked hydrogens is the least likely to react in the reaction shown below?
Hb Hc Hd He Ha NBS CCl4/h
a) Ha
b) Hb
c) Hc
d) Hd
e) He
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22. (4 pts) Radical-chain halogenation of 2,3-dimethylbutane gave three times more of 1-halo-2,3dimethylbutane than 2-halo-2,3-dimethylbutane. What halogenating reagent was used? a) I2 b) Br2 c) Cl2 d) F2 e) NBS
23. (4 pts) Treatment of an unknown compound with ozone followed by zinc in acetic acid gave the following four compounds:
O O O H O + (CH 3 )2CO + CH3 CHO + CH2 O
Which of the following could be the unknown compound?
O
O
O
I
II
III
a) I
b) III
c) I and II
d) II and III
e) I, II, and III
24. (4 pts) Assuming that all molecules are planar, which of the following molecules is/are aromatic? Lone pairs are not shown explicitly.
H N B H C
H B H O H
B N
B N
H H
A
B
D
a) A
b) B
c) C
d) D
e) C and D
25. (4 pts) What is the longest wavelength transition in acetone, (H3C)2C=O? a) * b) * c) * d) n * e) n *
26. (4 pts) 1-Methylcyclohexene is allowed to react with D2 (deuterium) in the presence of palladium adsorbed on carbon (Pd/C). What is the best description of the products? a) b) c) d) e) two stereoisomers, both with trans deuteriums one stereoisomer with cis deuteriums a mixture of two diastereomers a pair of meso compounds a pair of enantiomers
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27. (4 pts) Consider the following hydrogenation:
excess H 2 Pd/C
?
Which of the following reactants was used to exclusively obtain the above product?
a)
b)
c)
d)
e)
28 29. Some of the possible products of the electrophilic addition of HBr to 2-methyl-1,3-pentadiene are shown below (Z-isomers have been omitted).
Br A B Br Br C
HBr
Br Br D E
28. (2 pts) Which of the above bromides is not likely to form at all? a) A b) B c) C d) D e) E
29. (2 pts) What is the kinetic product of the reaction? a) A b) B c) C d) D e) E
30. (4 pts) What is the most likely protonation site in the conjugated alkene shown below?
a) c) d) e)
b)
=========================================================================== End of the exam
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Selectivity of halogen radicals (per H) 3o 2 5 1600 97000 2o 1 3.5 80 1100 1o 1 1 1 1
F Cl Br I
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Form A: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. D B B A2 D2 A B B2 E C B C2 A E2 C2 D2 D E D2 C C D C E E E A B2 A2 A
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