Final Exam - Summer 07

Final Exam - Summer 07 - Chemistry 322bL Final Examination...

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Unformatted text preview: Chemistry 322bL Final Examination page 2 August 6, 2007 I. (20 pts) Provide names for the following structures, or structures for the following names, as appropriate. Either IUPAC or common names are acceptable. (3) CH3 <1 ’ '° (2) Br or M‘ (b) O\\C/H o 3 m + \OCH3 2 - 2: our 9- (c) (E H ' " 4" *3- \ /C\\ /CH3 (3) H/ [Ca I CH3 CH3H H (d) fi‘ i? . CH3 “\(I3”C\CH;C‘NH-CHZCH3 2 " r — ll ammo —2- CH3C|3I+GH§CH2 Jren ‘\ NH—CH3 ’ If 3‘ (e) DMF (f) THF (g) acetic anhydride . g 0 Q m “ A“: /Q\ cu alias/"1 ‘CH M “'0'” U > 3 V343 (h) Name the following molecule as a derivative of galactose. Be sure to specify all the relevant information including ring size, anomeric configuration, absolute confi tion, etc. (The 7% molecule’s specific rotation is clockwise.) a r Mf’ 5 WI, 0 l ’ \ ( H OEt I I I I H OH HO III I 0 a $9 90 $1 1’ l N I '-r f E’ 4-— 0 l H HO H H 0 Chemistry 322bL Final Examination page 3 August 6, 2007 H II. (1} pts) (a) Complete the following partial structures so as to draw all reasonable resonance structures to complete a good representation for the indicated enolate anion. There may be more partial structures than you need. (Don’t forget the charge.) (b) Draw all additional reasonable resonance contributors to complete a good representation for the cation below. Partial structures are provided for your convenience. You may or may not need all of them. (+) H2 CH2 CH2 CH2 NH2 93 ‘ NH2 ‘ NH2 NH2 CH3O CH3O CH3O K) CH3O F F F / F 2 5\ CH , CH (W ‘ 2[qu2 1 2JFQH2 NH row) H H Q L uf’ CH3O CH3O H30 4 F F F G) Chemistry 322bL Final Examination page 4 August 6, 2007 22 7 , III. Wpts) Fill in the blanks or (circle?) the best answer for each of the following. (a) Label each of the following molecules as aromatic, anti-aromatic or non-aromatic. For simplicity, assume that all of these molecules are glanar as written for your assignment. CH3CH3 CH3 (EH3 (ftla CH3 \ /(+) 1., @ @“34a 0 O Q fmfic Qromfic We flog (mil groin (L (b) Circle g of the structures below that dopresent valid 112 molecular orbitals (bonding, nonbonding, or antibonding) for 1,3-pentadieny could be a radical, anion, or cation). Ignore the relative size of the contributing atomic orbitals. Light and dark lobes represent the “+” and “—” algebraic sign (not charge) of the atomic wave fimctions. 37.. @H / 3 © a Chemistry 322bL Final Examination page 5 August 6, 2007 (d) Which of the following undergoes solvolysis fastest and slowest in acetic acid? (Fill in TWO blanks.) NH2 CHaCHzCHz-Cl (g) For which of the following molecules is the rotational barrier about the RC(O)—X bond the largest? (4) ° ° 1 1 ° ’ CHg/lLoJYm3 CH3 Cl CH3 OCH3 CH3J\CH3 \, (h) Nucleophilic addition to the acyl carbon occurs fastest and slowest for which of the following? (Fill in TWO blanks.) O O (a) OPE/tone 0%,” loan A H3 faicd' ,s‘0_%sT C): (i) Which of the followin molecules reacts most rapidly with anhydrous HBr? Chemistry 322bL Final Examination August 6, 2007 (j) Which of these molecules is the most acidic? Which is the least acidic? (Fill in TWO blanks.) OH OH OH : No2 : : CN NH2 (2) (Pr: <0? OCH3 L 13. M w (k) Which of the following molecules is most acidic? Which is least acidic? (Fill in mg blanks.) CH3 /CH3 CH3 /CH3 CH§ /CH3 CH3 /CH3 CH3 /CH3 NH(+) NH(+) NH (+) NH (+) NH (+) CH3 CH3 (23 © <3 © N02 OCH3 OCH3 Am; (1) Which molecule reacts most rapidly with NaCN in methanol? ( I OCH3 Cl Cl CH30 OCHg Neg CN ON o OCH3 F CN (m) Which of these molecules is the most acidic? Which is the least acidic? (Fill in TWO blanks.) (Z) CHaO/G/COzH OZN/Q/CozH ©C02H HZN/G/C02H CHa/Q/COZH West [gait page 6 Chemistry 322bL Final Examination August 6, 2007 page 7 IV. (32 pts) Give the main organic product(s) for the following reactions, or provide reagents and conditions to carry out the indicated transformations, as requested. More than one step may be required for a given compound. Be sure to note product stereochemistry and/or regiochemistry wherever relevant. You do not need to balance the equation, show byproducts, or show any mechanism. “Workup” means treatment with water, dilute aqueous acid, or dilute base as appropriate to generate the product shown, followed by isolation of the product by appropriate means. (Note that “No Reaction” is always a possible answer.) H + CHSJLOJLCHE} \2/ ll 0 (b) CI“) 0 3' E O :Y econ {530 + WJ 9 (c) C¢CxC02Me MeO /CH2 OU/ m Meozc/ + Me \CH2 CH0 / \ 5 (d) gHz Cum" AICI3 ¢\‘, q ~04; CH3 0 + CH3'?'CH2_CI -—> E) large CH3 excess (5 (e) OH H 02 C\ /\/ &~CH ' H CrO / 3 HO-CH C 2 4 2\©/ I:lCHS H2504. H20. M acetone, 50 °C Chemistry 322bL Final Examination page 8 August 6, 2007 Q (0 NH2 1) NaN02,H20 ‘ HCIO°C ,/ - ,—> \ \ Br 2) CuCl, 60 °c 2V / (9 (II) Okefwmtcm CH3 m) HO O M82304 0 HO H (excess) O NaOH, H20 ,0 \ H OH \ c, OCH3 CH5 ‘/ (J{3 cxnfi (0 (+) (_) E; J! ‘Z‘IC I‘a NH3—CH—CO—NH—CH—CO—NH—CHz—COZ \‘\ CH(CH3)2 CH3 / \ 1) Ph—N:C=S, pH ~ 9 >-—\ 2) anhydrous HCI. CH3N02 0 man», 3) H30“), A (j) H—— OH Ho H PhNHNH2 (excess) HO H H OH H o HzOH Chemistry 322bL Final Examination page 9 August 6, 2007 O o H\ // H / (k) H-—— OH 1)KCN.HOAc C \6 HO H 2)Ba<0H>2. H2011 H H H H —’3 + M O H H o u )H o( ) HO H 4) Nit/Hg, H20, pH ~4 H ‘4” + H o H H OH . (h b th d t) H O . H S OW 0 pro UCS w H @“E‘ met (1H 0H H o CHZOH exkfl M 2 47 9 14on M Mfr“, CfiClic anoners '3 1“ Away“- (l) 9 (was. 0 0 catalytic NaOEt ‘ 'w‘k + CHFCH/C\CH3 HOEt Q IL?“ 0 5 HO— H CH30H H OCH; 0"} HO H solvent H O H H O u H 0“ ciliyéf H 0H + H OH H OH H CHzO “‘6 Hz 0 (n) (53 Chemistry 322bL Final Examination August 6, 2007 page 10 (0) R t H3 1) LiAIH4, Et20 L\’/l M Q “(I 2) workup ,cuCH (wt C: o O//C\CH3 ‘4 0 3 o (p) g ‘0” 0/ \CH3 6 /\./Cl-|C|-lJ CH30\C 1) NaBH4. MeOH \& U ‘ 8 2) workup R" V. (30 pts) Provide reasonable syntheses (i. e. , minimum number of steps, good yields, good stereoselectivity, good regiochemistry, etc. .) for the molecules shown below starting with the indicated starting materials and using other needed organic or inorganic reagents of any kind except as specified. For all of the syntheses below, show the molecular structure of any group or reagent at least once. Thereafter you may use an abbreviation if you wish. Be as specific as you can regarding reagents and conditions. Show the product formed from each important step of your syntheses. Be sure to indicate if a step results in formation of an ortho-para isomer mixture, but assume that such mixtures are readily separated. Do not show mechanisms. (a) 0” $265 H904» (LL96 //\ Q """"""" ' '> ‘<\ iQ/“\ G (' Br 01 S64 l-llsoq ‘ H.904 A Ito, 8" N o 2 A NH2 M on “1"” DR 90W / \ \, ——————-7 1&3!” Fe p”,3 K/\ 6r Com HO A Chemistry 322bL Final Examination page 11 August 6, 2007 (b) O $H3 ' COZEt CH-C Hz-CO» (» 002E! and CHa-CH=CH-C02Et - - - - - — - - - -> B xs MaDEt‘ ' “a” , 9mm ~ 00' L \/L\/“C”C“2C°¢” l 2) Hso Locr PT I) Hahn/HA 2) 0—05.13 C3 ,6 U can +'.c NaOEf * C0}: \ 2] \AC’WLHAcgEi- 1» How.) cubcil=Cllf04Ef L4 093 The two most commonly employed syntheses of racemic amino acids are the Strecker synthesis and the acetamidomalonic ester synthesis. LQ UC‘Me gm m gwm 3&3 (Data no] (c) Show how you would use the Strecker synthesis to prepare W1 and any other needed reagents. (Recall, the Strecker step uses NH4Cl and KCN.) (1; CH3 002‘“) CH3 I (+ I I CH30HCH20H20H ——————————— --> )Nl-la-CH—CH20HCl-la H .‘ <+> H + 0 04394 (ii—(£14 lI\IH2 cu) \ NC” 043914015 CH~CEN Cl} H10 CH3 {1;} (d) Show how to use the acetamidomalonic ester smthesis to prepare aspartic acid using ethyl bromoacetate. O n (+)NH3-CH—C02(‘) BrCHz—C—OEt ——————————— u» I CHz—fi—OH o cos Final Examination Bmoefln HoEi- Chemistry 322bL August 6, 2007 page 12 1 A CNN - ’ ~Co‘1E-L- cu‘cht l) NGOH I410; A 2) H :,0“ 2) g, cud‘cozet— ea 01—) ' N —-C|J ~CH (0 -‘~————' H3 2 L“ -602 (e) The artificial sweetener Aspartame®, shown below, is the monomethyl ester of the dipeptide NAspPhec. Given the side-chain monobenzyl ester of aspartic acid (Asp(OB ), shown below) for one of your starting materials, show a synthesis of Aspartame. O O (+) II II Aspartame = NAsp-Phec-OCH3 = NHa-‘Cle—C—NH—(l2H-C—OCH3 (EH2 CH2 W M H 0026) Asp(OB )= NHg—(IEH-Coz )(D‘er-l ~94 C01", 0 CH1 chHJ 93 CHz-COZCHzPh W (—) Phe = NHa-cle—coz O CHz-Ph OH$OH ' Cal-c1th C \ FLO 9! ~C|fi H1504 \—N=C:N_< ([20 m / NH NH -c‘H—co.,cH3 (or G > ‘ “4‘75 My CF3ch ‘9 “B {n (Ll-LC) "’2 a» Q 9w ‘3‘ A9Par+am 6—— NH; cu «ow—cu— coy} Chemistry 322bL Final Examination page 13 August 6, 2007 VI. (22 pts) (a) D-Exasperose, A below, is an aldohexose. Its structure is established by the data shown below, particularly by the observations that compound B is optically inactive, while E is optically active. Show each structure A-E with only the configurational information that you can conclude from its formation and the preceding structures. Then fill in the complete structure of A. Show all structures in their non-cyclic Fischer projection. Note: Even if you cannot establish the configurations, partial credit will be given for partial structures if they are sufficient to demonstrate that you know what the chemical transformations are. . [l H HNOa Q9 [4 H H20, A H OH CH20H D—preposterose, A l Bl'2, H20 E, optically active Chemistry 322bL Final Examination page 14 August 6, 2007 (b) Compound F, below, has a second isomer, G, with which it is in equilibrium in aqueous THF solution in the presence of catalytic quantities of HOH or H3O(+). (i) What is the structure of G? Chemistry 322bL Final Examination page 15 August 6, 2007 VII. (15 pts) Trehalose is a disaccharide that can be obtained from yeasts, fimgi, sea urchins, algae and insects. Deduce the structure of trehalose from the following data. Be careful to explain what each piece of information tells you about the structure, and then draw the actual structure. 1) Trehalose gives no reaction with Tollins’ reagent or Fehling’s solution. It does not form a phenyl osazone when treated with phenyl hydrazine. It does not mutarotate. 2) Acid hydrolysis of trehalose yields only D-glucose. 3) Trehalose is hydrolyzed to glucose by a—glucosidase but not by ,B-glucosidase enzymes. 4) Exhaustive methylation of trehalose followed by acid hydrolysis yields only 2,3,4,6-tetra-O- methyl-D-glucose. (gl'l‘he structure of trehalose is: I ’ TM r M Fchl'm ’9 eclilhq r mm W (D Mafimg duo/3%, 01) our madam ml osqzow. QOTMAQW . -'- bo+e\ womvwm QM shamed“, (D ediet momentum aru bjlucose ‘Ogac'd ingdmlagg %‘\’QM g\9€osid\'c ital-(aged. MA @ol'ex glbcoslolco M Ea M W «ow. (LB MOOMMOH 0%, 50 W ['mkagfié Wt 0M “Egg/flow L‘s/b. l oufiY'W’w" CH1. U410” 05 Ho / or u HO\ “ 0" H0 o 2 o H/ N Chemistry 322bL Final Examination page 16 August 6, 2007 VIII. (26 pts) (a) What is the 1° structure of a protein? CW 7‘61. AA 923W What is the 2° structure of a protein? LocaQ WO'HS'S M m o1~he\ixJ/b—slan2i') rancipm, What is the 3° structure of a protein? (B Tow 3D m 4 36“ (mam "[«éPgfiflEm/Z What is the 4° structure of a protein? ' new oieim 0L (D aggmém % WW Sum-Honda Cluc-lmr (b) To what must an enzyme bind most strongly to catalyze its reaction? +84 kralfl‘oii’lo’h Slim (C) Very briefly, what is speci 1c acid-base catalysis? . . i‘Dro-l'ovvlrahs Cir OCCu r' s beiou Morgan iZM <3? @‘Wjfig it 9H (mm m) (d) Very briefly, what is general acid-base catalysis? Why do enzymes often use general rather than specific acid—base catalysis to speed up their catalytic re ctions? If \ . Pro‘ltm “W “0‘” M“c\m¢2m ‘00” L‘ raor ' - W M W‘ (3 Au éulo it'd M51 tn2amw'0m3‘wl Wng - energy (Dwion ‘(m nega- inicv MW W 0’ 4&7 (e) The pH-rate profile for lysozyme catalyzed cleavage of : (glucNAc-murNAc)n oligomers is shown in Figure 1 at the right. What is the significance of the pHs corresponding to the two POints of 50% act‘ijcef N Is é m . “M i’ 4. (% Hafiz-H C 3W Chompcflm W9 activity Figure 1. Lysozyme pH-rate profile Chemistry 322bL Final Examination page 17 August 6, 2007 (t) Figure 2 at the right shows the proposed arrangement of the substrate (structurally simplified) and the principal lysozyme films) catalytic functional groups in the active site of the enzyme- 0 o substrate complex. Can you say anything specific about the | H relationship of the answer to part (e) above and the proposed gm c 0}“ structure of Figure 2? W Since As? Amado 53x LVC Oilpwz) ® it 6'“ 0‘ = Egg W M G' M MSW M 2 anxzisnrazzztsozaz2m?“ A D; (9 a =- 6).? (g) Show the generally proposed first step in the mechanism of polysaccharide chain cleavage catalyzed by lysozyme using the incomplete equation/diagram below. Draw curved arrows on the lefi side of the equation to show the “flow of electrons,” and complete the structures on the right side of the equation to show the outcome of the step. Briefly comment on how this would be a good example of general acid catalysis (if the hypothesis is correct). " G|u(35) G|u(35) C”) a (—ng Q9 0 62 “5 t? M —> RM"? OH 09 0 Asp(52) 0AAsp(52) w W Wfia formm GB % whose MR pNa Wig, glucNAc ' (9 (W61 \Muthlc CA‘HOV) ho/Jj‘acaihzeai [g Chemistry 322bL Final Examination page 18 August 6, 2007 IX. (22 pts) Write a detailed mechanism for each of the following reactions. Only the specified number of intermediate structures (in order from 1 to n if more than n are written) will be graded. A couple of points are given for the quality of the “arrow formalism” that you use. (a) Four intermediates. m Chemistry 322bL August 6, 2007 (b) Five intermediates Final Examination page 19 ...
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Final Exam - Summer 07 - Chemistry 322bL Final Examination...

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