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chemChem 3B-Fall08-mt2-Voldhart-soln

chemChem 3B-Fall08-mt2-Voldhart-soln - EXAMINATION 2...

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Unformatted text preview: EXAMINATION 2 Chemistry 33 Name: {521/ SID #: Print first ngfme before second! Use capital letters! Laboratory 68! (if applicable): Peter Voilhardt November 4, 2008 Please provide the following information if applicable. Making up an | Grade (If you are, please indicate the semester during which you took previous Chem SB: Semester Instructor Please write the answer you wish to be graded in the spaces provided. Do scratch work on the back of the pages. This test should have 20 numbered pages. Check to make sure that you have received a complete exam. A good piece of advice: Read carefully over the questions (at least twice); make sure that you understand exactly what is being asked; avoid sloppy structures or phrases. It is better to be pedantic in accuracy now than sorry later! Good Luck! DO NOT WRITE IN THIS SPACE I. ____ (25) n. ___,_ (50) ill. __ (50) iV. _ (45) v. _ (45) VI. _ (35) Total: __ (250) Chemistry 3B, Examination 2 Page 2 I. [25 Points] Write the organic products of the following reactions of the starting amide. H2804, H20 $0.“ 1. kgvk 2. H+, H20 work-up 1. LiA|H4 2. H“, H20 work-up Clz, NaOH Chemistry 38, Examination 2 Page 3 ll. [50 Points] Add the missing components (starting materials, reagents, or products) of the following reactions in the boxes provided. Aqueous work—up (when required) is assumed to follow each step. It is LL01 part of any answer. D20, NaOD Mass spectrum of product: m/z = 102 136 Spectrum of product: 200 180 160 140 120 100 EU 50 4O 20 D cos-uz-sus ppm Chemistry 38, Examination 2 Page 4 C. O O /. d. if CHacOOH --—P 0 e. 0 CH3 NaOH, H20, A H3C Chemistry BB, Examination 2 Page 5 f. 0 COOH 99C??? fl ix \ Cl 9. O 0 Ci CH3 h. o Chemistry SB. Examination 2 Page 6 HCI, 0 CHgCHgOH (solvent) / _,______.’. N Product after basic work-up Two additional neutral reagents Two reagents I Chemistry 33, Examination 2 Page 7 Ill. [50 Points] In an attempt to hydrolyze lactone A with concentrated aqueous HBr, a student obtained compound B. The complete spectral data for this product are shown below in the sequence: 1. 1H NIVIR, 2. 13c NMR, 3. Mass, 4. IR. HBr, H20 0 ——~———+ B (unknown) a. After consideration of the spectral data, write the structure of the product in the box below. Chemistry BB, Examination 2 Page 8 1 . 1H NMR spectrum (for expanded section, see bottom spectrum). 2H 1H ppm 2H 3 2H C D ‘2H 2H 2H | ppm Chemistry 33, Examination 2 Page 9 b. Draw again your suggestion for the unknown in the box and label the hydrogens A, B, C, and D giving rise to the corresponding signals in the spectrum. Use the Table below, if necessary. 3) (L :3) Type of hyd rogen" Chemical shift 8 in ppm Primary alkyl. RCH; 0.8— [.0 Secondary alkyl. RCHgR’ 1.24.4 Alma an“ “we“ like hydrogens Tertiary alkyl, R3CH 1.4—1.7 /CH3 Allylic (next to a double bond), RECHC 1.6—1.9 \R' Hydrogens adjacent Benzylic (next to a benzene ring). AICHQR 2.2—2.5 to unsaturated functlonal groups Ketone, RCHYCHJ 2.1w2.6 O Alkyne, RCECH 1.7—3.1 Chloroalkane, RCHJCI 3.6—- .8 Bromoalkane, RCI-lgBr 3.4»- .6 Hydrogens adjacent lodoalkane. RCH31 3.1—3.3 to electronegative Ether, RCHQOR' 3.3-3.9 atoms Alcohol, RCI-.l30H 3.3-4.0 Terminal alkene, R2C=CH3 4.6—5.0 } Alkene hydrogens Internal allcene, R2Cfi(lm 5.2—5.7 Rf Aromatic. ArH 6.0-«95 Aldehyde, REH 9.5—9.9 O Alcoholic hydroxy, ROH 0.5—5.0 (variable) Thiol, RSH 0.5—5.0 (variable) Amine, RNH; 0.5—5.0 (variable) Chemistry SB. Examination 2 Page 10 2. 130 NMR spectrum. 2 ill iéfl léfl 12in 1&0 lfii] BE 6’] Rib Eb U ppm Draw again your suggestion for the unknown in the box below and label the types of carbon atoms A and E3 giving rise to the corresponding signals in the spectrum. :3 WA (3,54. Chemistry SB. Examination 2 Page 11 3. Mass spectrum. Hint: Atomic weights: C = 12; H a 1; O = 16; Br exists in nature as a 1:1 mixture of Br = 79 and Br = 81. 5 am . 11 0 9|] 8|] "JD 50 5' 0 Well w toflH 30 213 M+ 1U 40 5|] El] 70 EU QEI 100 113120 130140 1513 1GB 17'0180 “IQIJ 200 MlZ 3. Clearly mark on the spectrum the molecular ion(s) as "ll/1+". b. In the boxes above the respective fragment ions, indicate the structure of the fragment. Chemistry BB, Examination 2 Page 12 4. ER spectrum. [00 TFNHEHI IHNEEI '5' tn 1: 1000 5000 2000 £500 £000 500 HFWENUl'lfl ERl-II Confirm the presence or absence (circle one) of the following bonds. Enter an approximate expected stretching frequency in the box. W“ W _1 3 (Caps—H) iSI figs—cm absent at N 2‘] S 0 cm ~ XJWNs- 1 v (O—H) is: present absent at {@310 (3 cm— ~ ,«r‘xw v (0:0) is: present absent at N l?OO cm"1 Chemistry 38, Examination 2 Page 13 IV. [45 Points] Write detailed step-wise mechanisms for the following transformations. Use only structures and “arrow-pushing" techniques. Note: These are 39; synthetic problems. Do not a_dg any reagents! What you see is what you have! a O ' o A/Lk Catalytic HO‘ A —-—-——-—I- / \ Work from left to right in the following spaces. There is more space than you will need. \ \ IO] .t __ ‘l H «63H if f ~——-—'-'~—e sky, as“... Chemistry SB, Examination 2 Page 14 b. O H“, H20 CHsCN ——-—+ NH2 Work from left to right in the following spaces. There is more space than you witl need. we //'"_”" “\H 1'ng f ‘i I’ +3, + Y +H2‘3 I; _ R—CfiN: :‘ [R—CEN—H <—> R—i =N—H] —“-,.—‘ /C‘\_. =+ -H "Hi! R o; “‘1 KAW .. NH v UNI-i3 NH2 NH2 (“3 it J: — J: $ L'Z‘. (—) H :2“ R/ “0H -H+ R/ ‘914 R/ “‘0” W R/ “‘0 Tu utumur uf mnitle {[3704} Chemistry 38, Examination 2 Page 15 c. O A HO“, H20 H0 H H 0 Work from left to right in the following spaces. STEP 1. Enolale gei‘ieralion Cfig ~ v .. “.5. ‘/O - HC—CHZ-i-W:QH \— H3C=C\ + H OH Small equilibrium concentration of enolate STEP 2. Nucleophilic allack (1143::me fl CHgle—CHQCH H STEP 3. Protonation :6:-/—:0\ O :0: i H 4 I ll CH3(IZ-CH2CH + 3-09]: wan—4 CH3(|3~—-CH3CH + Ho:— H H 50—60% 3-Hydr0xybutanal (Aldol) Chemistry SB, Examination 2 Page 16 V. [45 Points] Provide a reasonable synthetic route from starting material to product. Note: Several steps are required, and there may be more than one solution to the problem. Do not write mechanisms! Write out each step separately, including reagents and products. You need to apply retrosynthesis! O M i + any other material ---------------- * H Work from left to right in the following spaces. There is more space than you will need. Chemistry BB. Examination 2 Page 17 HOW OH """" * CN Work from left to right in the following spaces. There is more space than you will need. £2: H20 Q Wage; Nmoflf M g Wfiwujkgé —-—--——§ f D HOME-l Chemistry SB, Examination 2 Page 18 c. Synthesize ketone A from starting materials containing one or two carbons only. /\[(\/\ O A Work from left to right in the following spaces. There is more space than you will need. /‘ Agrjza Afifirfif & HEI’ NCL CM /\ ”i? —«—~——-=.> We . Z. “QCJ Mal-{- Mgr “”53 Chemistry SB, Examination 2 VI. Page [35 Points] Place an X mark in the box next to the most accurate statement. a. The reactivity of 1—4 toward H20 increases in the order ii i ii CH300| CHSCNHZ CH3000H3 1 2 3 D 1, 2, 3, 4 E 4, 3, 2,1 2, 3, 4,1 |:J 3, 2, 1, 4 b. The acidity of 1—4 increases in the order i ii CH3NH3+ 011300113 CHacOCHa 1 2 3 [j 1,2,3.4 |:J 4,3,2,1 l:| 2,3,4,1 3,2,1,4 ii if CHacOCCHg 4 HCOH 19 Chemistry SB, Examination 2 Page 20 0. Explain the following finding in one sentence. For the equilibria shown below, K1=“'1, but K2 >1 0 H+ O )L + CH30H —--~ A + H20 OH K1 OCH3 m ’mefg 4/; rpm gm: N ijigflafl Jag: K2 ) Wei)? 1,; WI Pmlassor Hennan paused when he heard that unmistakable lhucl -— another brain had lrnplodad. “The End” ...
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