F04 midterm2 key

F04 midterm2 key - Chemistry 30B Fall 2004 Second Hour Exam...

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Unformatted text preview: Chemistry 30B Fall 2004 Second Hour Exam November 12, 2004 M. E. Jung sawing” Signature TA Name Hand in answers written only on this paper, using the reverse side if necessary. No exams will be graded that do not contain your signature! Read each question carefully before you answer it. Answer the easy questions first. Good luck! WW :2. er #167 r; 71/ Law 9" MC/p/fiv/j/ $35 - - - - 2 - 2 - 3 — 0 - l l l l Chemistry 30B 2nd Hour Exam M. E. Jung Page 2 1. (12 points, 3 points each) a) Name the following compounds by the IUPAC, Chem. Abstracts, or common nomenclature system, unambiguously specifying any stereochemistry. CHO H >=< 2- 2'6 17‘" eZ'lmll’MaQ HOCH2 Cl Mi 6 CH0 0 b) Draw clear, unambiguous structural formulas (of the kind drawn above) for each of the following two compounds. 3,3-Dibromocyclobutanecarboxaldehyde 0th) /‘ Kt (E)—4—Bromopent-3—en—2-one 75 1 1“? 8r Chemistry 30B 2nd Hour Exam M. E. Jung Page 3 2. (12 points, 4 points each) Predict the major product(s) of each of the following reactions, showing stereochemistry whenever appropriate. If no reaction is expected, state No Reaction. Assume a normal aqueous workup after each reaction. a) CH0 (4 m NHZNHPh —_———* cat TsOH - M‘D b) 0074 J 0—— R2BH; ~90 . C=CH ———-'> : NaOH H H202 / T D c> om flaw» Lo p (1% (— H20) ; d :2) W CH3-Br "d 2) H30+ 3. (19 points, as indicated) Answer each of the following questions: (5) a) Explain clearly how 13C NMR would allow one to distinguish among the three compounds, A, B, and C using any technique we have discussed. H , a H .1 H ~ Lf floin “A it 6/5)“ 30 [UM/ML 26/64:,» {615% LPG/soc» :56 (3C (30 Chemistry 30B 2nd Hour Exam M. E. Jung Page 4 3. (continued) Answer each of the following questions: (6) b) Compounds D and E have the 13C NMR spectral data shown. Explain how one can use this information to assign structures to the two isomeric 3-hexenes, E—3—hexene and Z—3—hexene. Indicate which structure is D and which is E (write the letters under the structures) and indicate clearly what part of the data allows you to make this assignment. CompoundD: 131.0, 0.6,14.3 CompoundE: 131.2, 53? 13.9 H3CHZC H HSCHZC CHZCHa H CH2CH3 H H E D W%V%Wmsg\4hhw 'c C’s/QVCZOA [M6 I WE—XW WWI/Mawfiég 6/de yam ’ma'MWWW‘ ‘7 (8) 0) Explain clearly how one could use 1H NMR to distinguish between compounds F and G. Be sure to indicate exactly what one would see in the proton spectrum of both F and G. H CI 5" Me Me CI H Me Me H H F G W. ' WsfiufiflHQWM/QW ‘l’afl/flurmibéé‘éfij‘gMSA 12413 H4 WM/MQAQ «#334 q/ézygg 3327.] 9«//,§/3 )‘t Wflafl waSWJjfl¢ 547/3.- Chemistry 30B 2nd Hour Exam M. E. Jung Page 5 4. (10 points) Compound H, molecular formula C5H100, readily decolorizes Brz in CCl4 and is converted by H2/N i into compound I, molecular formula C5H120. Below is the 1H NMR spectrum of compound H. The 13C NMR spectrum of compound H shows signals at 146.12, 110.75, 71.05, and 29.38. Deduce the structures of compounds H and I. Remember to draw structures for both compounds H and I. C5H100 Compound A Chemistry 30B 2nd Hour Exam M. E. Jung Page 6 5. (12 points) Treatment of propanal 1 with excess methanol and catalytic sulfuric acid (with removal of the water in a Dean—Stark trap) affords a high yield of 1,1—dimethoxypropane 2. CH CH OCHs HSCACHO 3 HaCAclil + H20 cat. H2804 \OCH3 1 2 Write a detailed mechanism for the reaction, including all intermediates and resonances structures. You can use the shorthand notation that we have used in class (charges circled in one resonance structure and in parentheses to show where they would appear in other resonance structures). Also proton transfer between heteroatoms can be written as one step with the words ‘proton transfer’ over the arrow rather than showing the two steps, e. g., loss of a proton to solvent and then reprotonation of a different heteroatom in the subsequent step. N l g , . Chemistry 30B 2nd Hour Exam M. E. Jung Page 7 6. (22 points) A molecule called Benjamjljnh gave the following spectra: MS 100°' P7 Jul / ; 6‘ f 09926 W 5 I l 1 I rel : abund: I 0° : ' 4145 5859 120122 133140 m/z MM- IR ’“’ %Tlansmillance 13CNMR 2nd Hour Exam Chemistry 30B Page 8 M. E. Jung (continued): 6. v» mm v6 .2: u s g . . . W 6 E N v m 2 u s 5 M «J E E .2: ux 8 as a . H .H E Emineux 333:2 5:5 womcmnoxm/U 1H NMR (and expansion) mvmo.m «moo.«. ~cgawucHfi m p p Chemistry 30B 2nd Hour Exam M. E. Jung Page 9 6. (continued): Show what information each spectrum affords. Be specific! Indicate exactly what one learns from the data of each spectrum, e.g., ‘this peak indicates X, that peak indicates Y, etc.’ <3>Ms ,) mwwz am :7 8V :9 magmatic-15‘) s) logstZ/ij uflpfl 57/065c’g Br (“R #024 a/f 3373 (1)”CNMR CH'Wf’ 7‘0 5 3) Cff‘O Mbpbs%{8> (5)1H NMR ~> 0&1? Adj/.2 W "90“; w... ”’ MYO > \/H 2nd Hour Exam Chemistry 30B Page 10 M. E. Jung 7. (l 3 points, as indicated) Transform each of the given starting materials into the desired products by a reasonable route, namely provide the reagents and conditions. (NOTE: More than one step may be necessary for each conversion.) You may use any other normal organic and inorganic reagents as needed. (7) a) PthHO [kw Phi-5% Ph AR HO HH i [fin/WV; \\\ “w VA V a Mg" , “L; 7 VI 5 M W ) W} W b B 30 @Jbg (6) b) Br 0 ¢ 0 U L” MW 534/” f 140% \i/ viii/0 ...
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This test prep was uploaded on 04/05/2008 for the course CHEM 30B taught by Professor Rubin during the Fall '05 term at UCLA.

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F04 midterm2 key - Chemistry 30B Fall 2004 Second Hour Exam...

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