Chemistry 2130 Final Exam Fall 2017

1. Put the steps for recrystallization in the correct order.

1. Filter crystals, wash to remove adhering mother liquor.2. Filter hot solution to remove charcoal and other insoluble impurities.3. Treat with decolorizing charcoal.4. Dry crystals to remove last traces of solvent.5. Dissolve crude material in a minimum amount of hot solvent.6. Cool to effect crystallization.

a. 5, 6, 1, 3, 2, 4b. 5, 3, 2, 6, 1, 4c. 1, 2, 3, 4, 5, 6d. 5, 3, 2, 1, 6, 4

2. Compound X has a melting point of 100°C, the compound was not dried and a melting point was taken. The melting point will be:

a. 100-101°Cb. below 95°Cc. 85°C-100°Cd. above 100°C

3. What is the use of charcoal in recrystallization process?

a. It purifies organic solid compoundsb. It reacts with solid compounds and makes recrystallizaiton fasterc. It adsorbs colored impuritiesd. None

4. What method was used to separate a mixture of benzoic acid, p-nitroaniline, and biphenyl?

a. Densityb. Boiling pointc. Acid-base extractiond. Vapor pressure

5. Which is the best extraction method?

a. 4 extractions with 25 mL of solvent eachb. 3 extractions with 30 mL of solvent eachc. 2 extractions with 50 mL of solvent eachd. 1 extractions with 100 mL of solvent each

6. On a thin layer plate, the base line is 10 mm from the bottom, Compound A is 28 mm from the bottom and solvent front line is 80 mm from the bottom. What is the Rf value for Compound A?

a. 0.26b. 0.31c. 0.35d. 0.39

7. In normal phase chromatography, which is phase is more polar?

a. Stationary phaseb. Mobile phasec. They are the samed. Sometimes the mobile phase is more polar: it depends which solvent you use

8. What is the purpose of thin layer chromatography?

a. To check the purity of a compound.b. To determine the number of components in a mixture.c. To purify a large quantity of a mixture of components.d. Both a and b.

9. When we draw on TLC plates, what writing utensil is used?

a. Blue penb. Black penc. Pencild. Red pen

10. Simple distillation works best if the components boiling points differ by ______OC?

a. 10b. 20c. 50d. 80

11. What is the purpose of distillation?

a. To separate solid compounds.b. To separate immiscible liquid compounds.c. To separate mixed liquid compounds.d. To separate both solid and liquid compounds.

12. What is the product of the following reaction?

a. b.

c. d.

13. What statement is true about the Diels-Alder reaction?

a. This is a multistep reactionb. You always form 6 membered ringsc. Two dienes react in a cycloaddition.d. This reaction can proceed at room temperature

14. An amine group on a benzene is a(n) ____ director for electrophilic aromatic substitution.

a. Orthob. Metac. Parad. Ortho and para

15. What is the order of electrophilic aromatic substitution reactions?

a. Re-aromatization of the ring, attack of the electrophile by the ring, generation on the electrophile, resonance,

b. resonance, attack of the electrophile by the ring, re-aromatization of the ring, generation on the electrophile

c. Attack of the electrophile by the ring, resonance, re-aromatization of the ring, generation on the electrophile

d. Generation on the electrophile, attack of the electrophile by the ring, resonance, re-aromatization of the ring

16. Predict the product of the following reaction.

a. b.

c. d.

17. Which of the following compounds is most likely to react via SN2?

a. b.

c. d.

18. What are the characteristics of an SN2 reaction?

1. First order reaction.2. One step reaction.3. Inversion of configuration at the carbon atom that bears the leaving group.4. The reaction rate does not depend on concentration of nucleophile.5. Rate determining step is bimolecular.6. Second order reaction.7. Racemization of configuration at the carbon atom.8. Rate determining step is unimolecular.

a. 2, 3, 5, 6b. 1, 4, 7, 8c. 1, 2, 3, 5d. 2, 3, 6, 8

19. Which of the following mixed aldol condensation reactions will generate only one possible product?

a.

b.

c.

d.

20. Which is the most thermodynamically stable isomer of the following aldol condensation reaction?

a. E, Zb. Z, Zc. Z, Ed. E,E

21. Which reagent is used for the oxidation of isoborneol to camphor?

a. Sodium hydrideb. Sodium hypochloritec. Sodium borohydrided. Sodium sulfate

22. Which of the following reagents is the best to reduce an ester to an alcohol?

a. NaBH3CNb. NaBH4CNc. NaHd. LiAlH4

23. In oxidation/reduction reactions:

a. Oxidation is loss of electrons, reduction is loss of electronsb. Oxidation is gain of electrons, reduction is loss of electronsc. Oxidation is gain of electrons, reduction is gain of electronsd. Oxidation is loss of electrons, reduction is gain of elections

24. Isoborneol reacts with NaOCl in the presence of acetic acid to produce camphor. What is the purpose of the acid in this reaction?

a. Acetic acid is a solvent for this oxidation reaction.b. Acetic acid is necessary to convert NaOCl to HOCl. c. Acetic acid reacts with isoborneol, which facilitates the oxidation.d. Acetic acid is the oxidizing reagent for this oxidation.

25. When you made the ester or amide for your analgesic materials, what was the purpose of adding the acetyl group onto the molecule?

a. To make the aspirin more polar b. To make the acetaminophen more water soluble c. To make the aspirin more likely to partition into an aqueous layerd. To make the acetaminophen more bioavailable.

26. What is the role of potassium hydroxide (KOH) during the stilbene dibromide dehydrohalogenation.

a. solventb. acidc. based. leaving group promoter

27. Consider the combustion of carbon monoxide (CO) in oxygen gas:

2 CO (g) + O2 (g) 2 CO2 (g)

Starting with 122 grams of CO, calculate the number of moles of CO2 produced if there is enough oxygen gas to react with all of the CO. Molar mass of CO is 28.01 grams/mol

a. 4.36 molb. 122 molc. 0.229 mold. 8.72 mol

28. Given 1.10 grams of sodium carbonate and 1.10 grams of silver nitrate, 0.623 grams of silver carbonate are recovered from this reaction along with sodium nitrate. What is the percent yield? Na = 23 g/mol N = 14 g/mol O = 16g/mol Ag = 107.9 g/mol C = 12 g/mol a. 69.8%b. 21.8%c. 34.9%d. 143.3%

29. Salicylic acid reacts with acetic anhydride under acidic conditions to produce 2-(acetoxy)benzoic acid, also known as aspirin.

When 2.00 g of salicylic acid is allowed to react with 4.33 g of acetic anhydride, which is the limiting reagent?

Salicylic acid = 138.12 g/mol, acetic anhydride = 102.09 g/mol, aspirin = 180.16 g/mol, acetic acid = 60.05 g/mol.

a. Salicylic acidb. Acetic anhydridec. Aspirind. Acetic acid

30. Identify which of the following compounds corresponds to the IR spectrum.

a. b.

c. d.

31. Which of the following is not a purification technique covered in Chemistry 2130 Lab?

a. Recrystallizationb. Chromatographyc. Distillationd. Sublimation

32. What does a drying agent do and what is a common drying agent?

a. Removes organic solvents from aqueous layers: Mg3(PO4)3

b. Removes water from organic solvents: Na2(CH3CO2)2

c. Removes water from organic solvents: Na2SO4

d. Removes organic solvents from aqueous layers: MgSO4

33. If you have an aqueous mixture of the compound. Which solvent system, cyclohexane/water, pentane/water, or diethyl ether/water, would give the most efficient extraction into the organic solvent? The distribution coefficients for a compound are as follows:

Kcyclohexane/water = 1.5, Kpentane/water = 5.1, Kdiethyl ether/water = 11.2

a. Kpentane/water = 5.1b. Kcyclohexane/water = 1.5c. Kdiethyl ether/water = 11.2d. None

34. Which of these dienes gives the FASTEST reaction with maleic anhydride?

a. b.

c. d.

35. Which of the following compounds will undergo nitration at the meta position?

a. b.

c. d.

36. Why must everything be kept at or below -5°C in the following nitration reaction?

a. The nitronium ion is not a stable species.b. Hydrolysis of the ester can occur at higher temperatures.c. It is exothermic.d. All of the above.

37. Which of the following compounds will not undergo an aldol reaction?

a. b.

c. d.

38. Which of the following compounds is represented by the following IR spectra?

a. Acetone.b. Water.c. Phenol.d. Iodobenzene.

39. Calculate percentage yield: 7.408g CH3CH2COOH reacted with 13.897g SOCl2 to give yield of 2.776g CH3CH2COCl.H = 1 g/mol S = 32.07 g/mol O = 16 g/mol Cl = 35.45 g/mol

C = 12 g/mol

a. 25%b. 30%c. 35%d. 40%

40. Which of the following functional groups is represented by the box?

a. O-H b. C-Oc. sp3 C-Hd. Ester C=Oe. C=C

Answers1. b2. b3. c4. c5. a6. a7. a8. d9. c10. d11. c12. b13. a14. b15. c16. d17. a18. a19. c20. d21. b22. d23. d24. b25. b26. b27. a28. a29. a30. d31. d32. c33. c34. c35. c36. d37. d38. d39. b40. d