Chem 227 / Sample Exam 1

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1 Name Chem 227 / Sample Exam 1 Section Questions #1-30: Answer on Scantron; multiple choice (4 pts. each); T/F (2 pts. each). Questions #31 & #32 answer on the exam, point values indicated. [Exam=130 raw pts. total] 1. In the following compound, (I) how many chemically equivalent carbon atoms [i.e. the # of 13 C NMR signals], (II) the number of enantiotopic protons, and (III) the number of diastereotopic protons are there respectively? I II III A B C D E Which compound (M+/. m/z = 114) would show major fragment ions in its mass spectrum at m/z 85 and 57? A) C 2 C 2 CC 2 C 2 B) C 2 C 2 C 2 C 2 C C) C 2 CC 2 C 2 C 2 D) C 2 C 2 C 2 C 2 C 2 C 3. Barry Bonds is due go on trial for lying to a Grand Jury that he did not use an illegal growth promoting steroid, tetrahydrogestrinone (TG), the Clear. TG is one of the steroids below, which UV Spectroscopy can distinguish. What is the correct order of λ max values for the 3 steroids. [TG has the highest λ max value.] I II III I II III A. 239 nm 271 nm 314 nm B. 271 nm 314 nm 239 nm C. 314 nm 271 nm 239 nm D. 314 nm 239 nm 271 nm E. 271 nm 239 nm 314 nm

2 4. Which of the following absorption bands can be most easily used to distinguish between C 2 C(=)-N- and C(=)-N( ) 2? A) ~1700 cm -1 B) ~3000 cm -1 C) ~3300 cm -1 D) ~1450 cm -1 E) ~2950 cm Two unknown isomeric alkenes, X & Z, have a molecular formula of C They have nearly identical 1 NMRs. Each has one singlet and 2 doublets with very similar chemical shifts. The signals for the 2 doublets are downfield. Compound X has J = 16 z and Compound Z has J = 10 z. ne Chem 227 student considered that the compounds must be two of the following three possibilities. Which are they? C C C C C C C C C 3 3 C C C 3 C C C C C C 3 C C C3 3 C 3 I II III A) X = I; Z = III B) X = II; Z = I C) X = II; Z = III D) X = I; Z = II E) X = III; Z = II 6. ow many signals are predicted for the 1 NMR of the following compound? C 2 CNC A) 4 B) 5 C) 6 D) 7 E) 8 7. What is the multiplicity of the methylene hydrogens indicated in the proton NMR of the following compound? A. singlet B. doublet C. triplet D. quartet E. pentet

3 8. Which of the following would react the fastest with a strong base, such as NaN 2, to form a carbanion? 9. Which of the structures can be classified as aromatic? A. I and III B. II and IV C. II and III D. III and IV E. II only 10. Rank the following compounds in order of increasing rate of reaction when they are respectively reacted with a mixture of acetyl chloride and aluminum chloride. N 2 Br N 2 I II III IV A) IV < III < II < I B) I < IV < II < III C) III < II < IV < I D) III < II < I < IV 11. ow many isomeric tribromobenzenes are possible? A) one B) two C) three D) four C) five

4 12. Which point on the potential energy diagram corresponds to the species shown to the right for the electrophilic bromination of benzene with Br 2 /FeBr 3? 13. Which of the following reactions is not a reduction? A. reaction of an 1-butyne with sodium and liquid ammonia B. reaction of an butyraldehyde with sodium borohydride C. reaction of 2-butene first with borane (B 3 ) followed by - / 2 2 D. reaction of 2-butyne with sodium and liquid ammonia E. reaction of acetophenone with hydrazine and Na 14. An unknown compound has the following 13 C NMR. Identify the compound from the list of structures below it. CC 2 C 2 C 2 C 2 A B C D

5 15. The IR of an unknown indicates an ester with the molecular formula of C The compound s proton NMR follows. Identify the compound from the list of structures below. mulitplet A B C D E 16. Starting with toluene, which of the following is the best method to make the ether shown below? (Assume you can separate ortho and para isomers.)

6 17. Which of the following is in the correct order of increasing oxidation number? A. butyne < butene < butanol < butanone < butanoic acid B. butyne < butene < butanol < butanoic acid < butanone C. butanoic acid < butanone < butanol < butene < butyne D. butene < butyne < butanol < butanone < butanoic acid E. butanoic acid < butanone < butanol < butyne < butene 18. Which of the following has the lowest heat of reaction on catalytic hydrogenation? (4 moles of 2 per mole of hydrocarbon) 19. Which one of the following reactions does not produce tert-butylbenzene? A. benzene + ( ) 3 C/AlCl 3 B. benzene + ( ) 2 C=C 2 / 2 S 4 C. benzene + ( ) 3 CCl/AlCl 3 D. benzene + ( ) 2 CC 2 / 2 S 4 E. benzene + ( ) 3 C/ 2 S The respective 13 C NMR chemical shifts for the compound below are δ 15.8, 40.1, 51.8, ppm. Which of the carbon assignments is correct? A B C D C C N C End of Multiple Choice True (A ) / False (B) hexen-2-one has a higher IR carbonyl frequency than 2-hexanone. 22. Lithium aluminum hydride will reduce 3-hexen-2-one but sodium borohydride will not. 23. In Electrophilic Aromatic Substitution reactions all electron withdrawing groups de-activate and most direct to the meta position.

7 24. 1,1,2-trifluoroethyl benzene reacts slower than 1,1,2-trichloroethyl benzene with iron (III) bromide plus bromine. 25. There is better value in burning benzene vs. cyclobutadiene as fuel in an automobile. (Assuming the same relative amounts and the same prices per gallon). 26. There are 0 nodes in the following bonding orbital diagram of benzene. 27. The following 2D-NMR represents Carbon ydrogen Correlation Spectroscopy (CSY), which allows identification of coupled protons. 28. The 1 NMR of primary alcohols will have one more peak in the NMR when D 2 is added. 29. The compound below is best named as 1-methyl-2-nitrobenzene. N Tylenol, aspirin, ibuprofen, and several other analgesics all have a substituted aromatic ring in their respective structures, as does the compound above. Therefore, if the compound above were taken after completing this exam, it would definitely cure my headache. End of True/False

8 31. (15pts) Friedl-Crafts acylation of para-chloroanisole produces predominately one product with tiny amounts of a minor by-product. Provide structures for the major and minor products and their respective intermediates. The electrophile is shown. + C C3 - + Cl C + Intermediate I major product - + Intermediate II minor product Label the reaction coordinate diagram below for the two products: label the major product (X), the minor product (Y), the respective intermediates as (I) and (II), and all Transition States as (TS). Draw the resonance structure of the starting material in the box which explains the formation of the major product. Resonance Structure: Δ G Reaction progress The reactions are endergonic / exergonic. (Circle one.) Briefly explain why the major product forms over the minor.

9 32. (15pts) a) Provide a synthesis of the product below from benzene using as many steps and reagents as you find necessary. Be certain that the reaction chemistry for each step is correct and indicate all of the reagents in each step. [NTE: Four steps would likely be average.] Cl 2 N a) Provide structures and reagents for the reaction sequence below. Na 2 Cr 2 7 PCC +