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347practice_exam_spring_2007_final_exam

347practice_exam_spring_2007_final_exam - YOUR NAME...

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Unformatted text preview: YOUR NAME: Chemistry 347 Final Examination Spring, 2007 Professor Hopkins /14 /14 /6 /8 /8 /8 /6 /8 /5 ,/5 /9 /9 090999555‘0507‘ was .Nz—uO' Total: /100 You are responsible for confirming that this examination contains 13 pages, including the cover sheet. 1. (14 points) Draw the chemical structure of each of the following substances. For example, “cyclohexanol” is: OOH a. Dicyclohexylcarbodiimide b. Dicyclohexylurea c. The 2,4-dinitrophenylhydrazone derivative of 2-propan0ne (acetone) (1. The organic liquid that causes “cloudiness” when 1,1—dimethylethanol (tert—buyl alcohol) is subjected to a Lucas test. e. The organic product that results from subjecting benzaldehyde to a Tollens test. f. The multi-carbon organic product that results from exposing 2—hexanone to an iodoform test. g. The organic product derived from 2-amin0propane (iso—propylamine) after an acetyl chloride test. 2. (14 points) In each case below, you are provided a SINGLE SAMPLE that contains a single pure substance that you know to be one of the two indicated substances. Name (no need to describe details) what single “wet” test (chemical test, solubility test, etc., NO SPECTROSCOPY!) you would use to establish which of the two is the correct structure for the substance. Additionally, describe briefly how the result would be interpreted (sample answer: “if mix turns cloudy then first; if not, then second.” You have NO authentic samples available, and NO tables of derivative melting/boiling points. a. H 0 0 3 Test: Interpretation: b C/ O H a O H Test: Interpretation: C H) C H 3 ‘ NH c. N C H 3 H C /i\/\/ 7— HC‘, ’ 3 3 Test Interpretation C. H Test: Interpretation: \ (:0 H Test: Interpretation: C H 3 H C Test: Interpretation: (M l g' tic/fat), HEMH} 3 0 Test: Interpretation: 3. (6 points) Reproduced here is a portion of the 200 MHz proton NMR spectrum of a crude mixture from peracetylation of D-glucose. 6.5 6.4 6.3 5.2 6.1 8.0 5.9 5.8 5.7 5.6 pm (a) Draw the chemical structures of the two isomeric peracetylated forms of D-glucose. (b) Assign a single proton in each structure to one of the two resonances shown in the proton NMR. (0) Correlate the observed magnitude of the J -coupling to the structures you have drawn (using the empirically determined relationship of size of J —coupling to dihedral angle). (d) After recrystallization of this mixture, the melting point is quite sharp (109—1100). How do you predict the above proton NMR spectrum would differ for the product of recrystallization? 4. (8 points) H HO I ‘ WMHL’E / 1L“: {ii/kWh, / H + l N1 \p/ N/ \H "l R (a) In your assay for dihydrofolate reducatase activity, you monitored the loss of ultraviolet absorbance of samples at 340 nm. What substance in the equation above absorbs light at this wavelength? What substance (evidently) does not (or absorbs less)? (b) Methotrexate is a powerful inhibitor of dihydrofolate reductase. Describe how you use d: ‘ methotrexate as a positive control to check your assay. (0) Explain in words (chemical structures not needed, unless you wish) why the chemical reaction above is critical to humans (and the parasite that causes malaria). 5. (8 points) In your sulfa drug synthesis, you protected an amino group using an acetyl derivative. In your dipeptide synthesis, you protected an amino group using a more complex (and more expensive) carbobenzyloxy (CBZ) group. In the space below, use chemical structures and words to explain clearly Why it is that if you had instead'used an acetyl group in the dipeptide synthesis, the conditions for its removal would have destroyed your desired product. . (8 points) The amines you used in the sulfa drug synthesis were categorized as “easy”, “harder”, and “even harder”. Sort the amines below into these three categories (Hint: two in each box; use all six compounds). Using the fact that the sulfonamide coupling reaction is sensitive both to steric crowding and electronic effects, explain why each amine is in its category. CH / MM _\ é :\ f l \ N01, CH3 \ Write “easy” amines Write “harder” amines Write “even harder” amines 1n thls box in this box in this box Explanation: For problems 7-12: Full~ credit will be given for the correct structure. If you provide the WRONG structure, then to receive partial credit you should explain the data to the extent you can. 7. (6 points) Identify compound 7 given the following. Formula: C11H14O. Gives positive 2,4-DNP test. Negative with acetyl chloride. Burns with a sooty flame. Insoluble in dilute aqueous HCl, dilute aqueous sodium bicarbonate, and dilute aqueous sodium hydroxide. Soluble in concentrated sulfuric acid. Proton NMR and IR shown. q % TRANSMITTANCE 8. (8 points) Identify compound 8 given the following: Formula: C10H14O. Gives negative 2,4—DNP test. Positive with acetyl chloride. Gives negative bromine in dichloromethane test. Insoluble in dilute aqueous acids or bases or all kinds. Proton NMR and IR shown. 100 80 60 4o 20 4000 3000 2000 1600 1200 1000 - 900 600 WAVENUMBERS (0M4) - 250 0 Hz Hintfl’air of diastereotopic hydrogens. 9. (5 points) Identify compound 9 given the following. Formula: C5H9N. Gives a negative bromine in dichloromethane test. Gives negative acetyl chloride test. Proton NMR and IR shown. :25“)- 15 ‘5 17 1319 21 23' 14 13 12 10 MICHONS 6 5.5 3.5 3330 anon $400 5200 soon mo 2500 Mo 2200 mu 23 2.4 2.5 2.8 2.72.8293 600 1500 WAVENUMBERS NICOLET ZOSX FT-IR H'" a“ l0 10. (5 points) Identify compound 10 given the following. Formula: C6H10. Positive bromine in dichloromethane test (no evolution of HBr). IR shown. Proton NMR spectrum: two singlets in a ratio of 9:1. mcnons _ 1.2 as 2.4 2.5 La 2.1 2.329 a 3.5 4 5 5.5 e 7 a 9 w 12 1a 14 15 1s 11 1319- 21 2: 25. m 4—H ' . on no N . no M ,5 , 7o! s; 0, ”IA '3 so '1‘ u T to 7 u a . so c u E M 3" 0.1 10 g 0 i : : ; "1° woo 4400 4200 won am 3500 3400-3200 soon mo 2300 2400 2200 2000 woo woo 1400 1200 moo aoo son «an WAVENUMBEns NIGOLET zosx FT-lFl H 11. (9 points) Identify compound 11 given the following. Molecular weight: 118 g/mol. Combustion analysis: 40.7% C, 5.1% H, no N, S, or halogens found. Gives negative 2,4-DNP test. Soluble in water. Dissolves in dilute aqueous sodium bicarbonate with evolution of bubbles. Titration of a solution of 11 in water (10 mL, 0.1 M in 11) using phenolphthalein as a pH indicator required 20 mL of 0.1 M aqueous sodium hydroxide to reach neutral pH. Proton NMR and IR shown. MICRONS 11 12 13 14.15181 IV__| :l‘irl :l5=IEJ .g‘; . 1:. '-‘. ,," 2.8 " moz>-4-.-I—:mz>=a-' $3.? WW '3 3 M “00 4200 4000 3300 3800 3400 3200 3000 2800 2600 2400 2200 2000 1300 1800 800 400 . WAVENUMEERS ' NICOLET ZOSX FT-IR 1mm 2 [go N‘ H7; mmmnnn H mg will”! u in ~ {null so lillllg, l“ 1.; .I HI -| l l2. 12. (9 points) Identify compound 12 given the following. Mass spec: Gives molecular ions at m/e 171 and 173 in a 1:1 ratio. Peaks at m/e 172 and 174 are about 7% as large as those at m/e 171 and 173. Insoluble in dilute aqueous sodium bicarbonate or sodium hydroxide, but soluble in dilute aqueous HCl. Gives positive acetyl chloride test. Treatment with cold acidified sodium nitrite, followed by treatment with B-naphthol gives a brilliantly colored precipitate. Proton NMR and IR shown. MICRONS 1002.2 2&3 1: 2.5 216 217 738 2.3 :11 3.5 4 4.5 5 5.5 9 10 11 12 13 14 15 16 17 1319 21 23.25 aoo WAVENUMBERS NICOLEr ZOSX FT-IR RV ...
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