Organic Chemistry Laboratory Final Exam Spring 2014 Test Form A: Questions and Solutions PDF

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Download Organic Chemistry Laboratory Final Exam Spring 2014 Test Form A: Questions and Solutions PDF

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CHEMISTRY 237 FINAL EXAMINATION SPRING 2014 TEST FORM A

Do Not Open this Booklet until Told to Do So.

Each multiple choice question is worth four points. Fill in the best answer for each question on the Scantron sheet provided.

When you have completed the exam:

1. Make sure your Name, UIN, and Test Form are bubbled in on your Scantron form. 2. Fill in the blanks on the back of this page, sign and remove this page from the exam packet. 3. Turn in two pages – the Scantron and This Page. 4. Show your picture ID to the Instructor of this Exam. 5. Sign your name on the signature sheet provided. 6. Quietly leave the room. – No conversations with your TA (or other persons) are permitted during the exam, while in the exam room! When you have completed the exam:

Do Not Open this Booklet until Told to Do So.

CHEMISTRY 237 TEST FORM A This exam will only be graded if this page is submitted with the Scantron. Fill out the information below before turning this page in to the Exam Proctor.

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TA:

________________________________

Date:

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Lab Day:

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YOU MUST TURN IN THIS PAGE OF THE EXAM WITH YOUR SCANTRON

Chemistry 237 – Spring 2014

Final Examination – Form A

Choose the most correct answer: (4 points each) 1. The two characteristics of a bond that affect the frequency of infrared radiation absorbed by that bond are: a. size of atom and number of atoms b. size of atom and bond strength c. molecular weight and bond strength d. number of atoms and molecular weight e. none of these

2. Which of the following is correct about a phase transfer catalyst? a. It is part of the product. b. It makes a two layer system into a one layer system. c. It gets used up completely in the reaction. d. It removes the product of the reaction as it is formed. e. It transports the reactant between phases. 3. Which structure below will have the highest strain energy when calculated by molecular mechanics?

a.

d.

b.

e.

c.

4. Which of the following could be used to test for the presence of tertiary alkyl chlorides? a. Bromine test b. Silver nitrate test c. Baeyer’s test d. Ferric chloride test e. Lucas test

Form A – Page 3

Form A – Final Examination

5. The ferric chloride test is used as a qualitative test for: a. alcohols b. alkyl halides c. Phenols

Chemistry 237 – Spring 2014

d. e.

nitro compounds alkenes

6. In the determination of a melting point, indicate which of the following statements is false. a. An impurity usually raises the melting point of an organic compound. b. A eutectic mixture has a sharp melting point. c. An impurity usually lowers the melting point of an organic compound. d. It is important that the height of the sample in the capillary be only 1-2 mm, and that it be packed firmly. e. The lower end of the melting point range is the temperature at which the first drop of liquid is seen.

7. Ketones can be obtained in good yield by oxidizing: a. primary alcohols b. secondary alcohols c. tertiary alcohols d. quaternary alcohols e. gem-diols

8. The word(s) that describes one vaporization and condensation step in a distillation is: a. reflux ratio d. volatility b. azeotrope e. theoretical plate c. fractional distillation

9. What should you do if you spill sulfuric acid on your hand? a. Wash it with water and apply 0.6 M sodium thiosulfate solution. b. Wash it with water and apply 0.6 M sodium sulfate solution. c. Wash it with cold water and 0.6 M sodium hydroxide solution. d. Wash it with cold water and apply 0.6 M sodium bicarbonate solution. e. Wash it with cold water and dilute acetic acid solution.

10. In the solvolysis of the 1-phenyl-1-chloroethane (R-Cl) with water, the reaction is: a. second order in H2O b. independent of the amount of R-Cl present c. first order in both H2O and R-Cl d. faster in 50:50 water:ethanol than in 60:40 water:ethanol because the cationic intermediate is more stable in the 50:50 medium e. independent of the amount of water

Form A – Page 4

Chemistry 237 – Spring 2014

Final Examination – Form A

11. An aqueous solution of this reagent will extract p-nitroaniline from a dichloromethane solution of p-nitroaniline, benzoic acid and naphthalene: a. hydrochloric acid b. sodium chloride c. sodium hydroxide d. both b and c will work e. all a, b and c will work

12. In phase transfer catalysis experiment, what kind of catalyst was used? a. sodium hydroxide b. methylene dichloride c. allyl bromide d. quaternary ammonium salt e. naphtholate anion

13. Which of the following molecules would you expect to have no dipole moment?

1.

a. b. c.

2.

3.

1 2 3

d. e.

1 and 2 none of these

14. In the following E2 reaction, what would the expected product(s) be?

1.

3.

2.

4.

a. b. c. d. e.

3 and 4 1 and 3 2 and 4 1 only 2 only

Form A – Page 5

Form A – Final Examination

Chemistry 237 – Spring 2014

15. Which of the following statements regarding recrystallization is true? a. As the amount of impurity increases, the loss of pure product decreases. b. Two substances with nearly equal solubility behavior, present in equal amounts, may be easily separated. c. It is undesirable to have a high concentration of solute near the boiling point of the solvent. d. To achieve a high recovery of pure crystals, the solute should be dissolved in a minimum amount of solvent when the solvent is near its boiling point. e. A good recrystallization solvent should dissolve a large amount of the impure compound at all temperatures.

16. The advantage of steam distillation is that it allows the distillation of: a. water soluble compounds that possess a high boiling point b. water insoluble compounds that possess a high boiling point c. water insoluble compounds that possess a low boiling point d. water soluble compounds that possess a low boiling point e. ionic compounds

17. From the TLC below what is certainly true about the composition of the unknown (U) sample?

a. b. c. d. e.

A and B are present A and C are present only C is present only A is present B is not present in the unknown

18. In the oxidation of cyclohexanol to cyclohexanone with bleach solution, the oxidation state of what element is reduced? a. Cr b. hydrogen c. Cl d. O (of hypochlorous acid) e. C (attached to C=O of acetic acid)

Form A – Page 6

Chemistry 237 – Spring 2014

Final Examination – Form A

19. Which of the following statements about gas chromatography is false? a. GC can be used as a quantitative tool for determining composition of a mixture b. GC may be used to separate compounds with limited thermal stability c. GC requires that compounds have reasonable volatility d. GC is preferred when a great amount of mixture is available for separation e. GC can separate compounds with close boiling points if their functionality is different

20. The pieces of glassware labeled A and B respectively are called: a. A: funnel; B: graduated Erlenmeyer b. A: Büchner funnel; B: Erlenmeyer flask c. A: Büchner funnel; B: filter flask d. A: Hirsh funnel; B: filter flask e. A: Hirsh funnel; B: Erlenmeyer flask

A

B

21. Joe Aggie performed a kinetic study of the SN1 solvolysis reaction of 1-phenyl-1-chloroethane using a 40% H2O, 60% ethanol mixture for solvent. What effect would occur if he uses an 80% H2O, 20% ethanol mixture? a. the rate would decrease b. the rate would increase c. the rate would remain unchanged d. the solution would remain acidic longer e. the acidity of the solution would double

22. When you want to remove the excess dissolved water in an organic phase, the easiest way is to wash this solution with brine. What is brine? a. CaCl2 d. saturated NaCl solution b. saturated MgSO4 solution e. saturated NaBr solution c. ethanol saturated water solution

23. The preparation of 3-chloro-3,7-dimethyloctane from 3,7-dimethyl-3-octanol is an example of: a. an SN1 reaction d. an elimination reaction b. a halogenation reaction e. an SN2 reaction c. an oxidation reaction

24. When benzoic acid is mixed with inorganic sand, what happens to the melting point of the sample? a. increases b. decreases c. stays the same d. increases above the actual melting point, then decreases e. goes below the eutectic point

Form A – Page 7

Form A – Final Examination

Chemistry 237 – Spring 2014

25. In thin layer chromatography, the observed Rf will change upon changing any of the following parameters, except: a. the solvent b. the functionality of the compound c. the absorbent d. the level of saturation of the developing chamber with solvent vapors e. the distance traveled by the solvent front

26. Which is a positive test result for the presence of an oxidant using the potassium iodide-starch test paper? a. appearance of a blue-black color b. disappearance of a blue-black color c. appearance of a red color d. disappearance of a red color e. no color change

27. Which of the following is an effective means to increase separation between two peaks (i.e. increase resolution) on the GC spectrum? a. Increase carrier gas flow rate b. Increase column temperature c. Decrease the thickness of the stationary phase d. Inject the sample more slowly e. Increase the length of the column

28. An experiment that started with 20g of Compound A (MW 200. d=1.50) resulted in 5g of Product B (MW 100, d=0.50). Based on the equation below, what is the percent yield?

A a. b. c. d. e.

B

25 50 75 0.25 0.75

29. Simple distillation is most effective in separating compounds with: a. almost identical boiling points b. greatly different densities c. widely different boiling points d. different colors e. different Rf values

Form A – Page 8

Chemistry 237 – Spring 2014

Final Examination – Form A

30. Which of the following functional groups would have a peak between 1670-1830 cm-1 in an infrared spectrum? a. aldehyde b. amide c. ketone d. a and c e. all of the above

31. Which of the compounds below could be used as a phase transfer catalyst for a reaction of naphtholate anion with an alkyl halide? a.

b.

c.

d. e.

32. Acetic acid and ethanol both contain -OH peaks in their IR spectra, however, they can be easily differentiated by a peak near: a. 3300 cm-1 b. 3000 cm-1 c. 2260-2215 cm-1 d. 1700 cm-1 e. 2150-2100 cm-1

33. Why is the substitution product favored in the preparation of 3-chloro-3,7-dimethyloctane? a. no good nucleophile is present b. an excess of nucleophile is present c. the reactant and product are soluble in the solvent d. a stoichiometric amount of Nu- is present e. an equilibrium is set up between the reactant and product

Form A – Page 9

Form A – Final Examination

Chemistry 237 – Spring 2014

34. Stearic acid and eugenol (main constituent in oil of cloves) belong to what classification of natural products? a. acetogenins b. terpenes c. steroids d. alkaloids e. phosphates

35. Successful purification of an impure solid is reflected in the melting range of the solid after each recrystallization. If purification is occurring then the range should become: a. narrower and the upper limit lower b. broader and the upper limit lower c. broader and the upper limit higher d. no change, the range should stay the same e. narrower and the upper limit higher 36. From the following compounds, which one is the most reactive toward dehydrohalogenation by strong base? a. b.

c.

d. e.

37. Which of the following factors does not affect the retention time of a compound in gas chromatographic analysis? a. the solvent in which the compound is dissolved for injection b. the temperature at which the column is maintained c. the rate of flow of the column gas d. the length of the column e. none of these, all affect the retention time

Form A – Page 10

Chemistry 237 – Spring 2014

Final Examination – Form A

38. Based on VSEPR, what is the hybridization of the nitrogen atom and the approximate bond angles around nitrogen in methylamine, CH3NH2? a. sp and 120 b. sp and 180 c. sp2 and 109.5 d. sp2 and 120 e. sp3 and 109.5 39. If you do a kinetic study of SN1 solvolysis, which graph is correct?

a.

d.

b.

e.

c.

40. Which of the following is not a desirable characteristic of a solvent to be used in an extraction? a. The solvent should be immiscible with the solvent of the solution. b. The solvent should have the most favorable distribution coefficient for the component which is to be separated and the most unfavorable coefficients for the impurities or other components. c. The solvent should not react chemically with the components of the mixture. d. The solvent should be readily separable from the solute. e. The solvent should be non-volatile.

Form A – Page 11

Form A – Final Examination

Chemistry 237 – Spring 2014

41. In the reaction of allyl bromide with naphthol using phase transfer catalysis: a. DMF was the solvent d. a and b b. the reaction mechanism was SN1 e. a and c c. the reaction mechanism was SN2

42. In considering the conformations of n-butane generated by 360 rotation about the C2-C3 bond, how many different energy values will be encountered as energy minima? a. Two d. Three b. One e. An infinite number c. Four

43. The term antiperiplanar in an elimination reaction means: a. the product alkene has a dihedral angle of 180 b. the alkene distribution follows the Zaitsev rule c. the abstracted proton and the leaving group are on the same atom d. the abstracted proton and the leaving group have a dihedral angle of 180 e. the planes of the abstracted proton and the leaving group are perpendicular

44. Which of the following statements is false for recrystallization as a method for purification of organic compounds? a. Low solubility of the compound at low temperatures minimizes the amount of the purified compound that will be lost during recrystallization. b. If the impurities are soluble, they may be removed by filtration at high temperatures. c. Scratching the side of the beaker with a stirring rod may induce crystallization. d. Recrystallization is often used to purify solids. e. A good recrystallization solvent should be reasonably volatile.

45. The structure of limonene is a.

d.

b.

e.

c.

Form A – Page 12

Chemistry 237 – Spring 2014

Final Examination – Form A

46. You have carried out a thin layer chromatography of a sample of benzoic acid. Measuring from the bottom of the sheet, the origin was at 10 mm, the solvent front at 90 mm and the center of the benzoic acid spot was at 30 mm. If you rerun it on a larger sheet so that the origin is at 10 mm and the solvent front at 130 mm, where will the benzoic acid spot be (measured from the bottom of the plate)? Hint: Draw representations of the TLC sheets! a. 30 mm b. 40 mm c. 60 mm d. 43 mm e. 90 mm

47. Which of the following starting materials would yield the following product?

a. b. c. d. e.

2-heptanol 2-hexanol 1-hexanol 1-heptanol 2-methyl-2-heptanol

48. Assuming you had a mixture of the following compounds, which one would elute first on a GC that contains a polar poly-alcohol (Carbowax 20m) column? a. hexane b. 1-hexanol c. 1-aminohexane d. hexanal e. 3-hexanone

49. Volatile organic compounds should: a. be handled carefully to avoid explosions b. not be kept in closed containers c. be transferred in the hood d. be handled only with polystyrene gloves e. all of these

50. A student was given 2.00 g of a very impure solid. After recrystallization and drying the student obtained 2.00 g of recovered material. Which of the following statements is true? a. The recrystallization yield of pure compound was 100%. b. The melting point range should be broader and the upper limit higher. c. The melting point range should be narrower and the upper limit lower. d. Since all of the material was recovered, no purification occurred. e. The melting point range was broader and the upper limit lower.

Form A – Page 13

Form A – Final Examination

Form A – Page 14

Chemistry 237 – Spring 2014

CHEM237 TestVersionA Q# 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

ANS B E D B C A B E D E A D A B D B E C D C B D A C E

Weight 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

Q# 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

ANS A E B C E C D B A E C A E C E C A D B A B A A C D

Weight 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

CHEM237 TestVersionB Q# 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

ANS ANS E B C E C D B A E C A E C E C A D B A B A A C D

Weight 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

Q# 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

ANS B E D B C A B E D E A D A B D B E C D C B D A C E

Weight 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

CHEM237 TestVersionC Q# 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

ANS E C A D B C D C E B D B A D A E D E B A C B D E B

Weight 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

Q# 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

ANS D C A A B A B D A C E C E A C E A B D C E C B E A

Weight 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

CHEM237 TestVersionD Q# 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

ANS D C A A B A B D A C E C E A C E A B D C E C B E A

Weight 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

Q# 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

ANS E C A D B C D C E B D B A D A E D E B A C B D E B

Weight 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4...