Final Exam - Summer 08

Final Exam - Summer 08 - Chemistry 322bL Name Emil CBC/{42F...

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Unformatted text preview: Chemistry 322bL Name Emil CBC/{42F Basic Organic Chemistry August 11, 2008 FINAL EXAMINATION Read each question in its entirety before beginning your answer. Answer the followmg questions in the space provided. Please organize your thoughts and attempt to make your answer as legible as possible. If we cannot read your answer, it cannot be given credit. Please remember that C-C-C-C without hydrogens and “stick” struch representations will be given N0 credit (except for rings only). You may use the backs of pages for scratch paper. I. (26) II. (3?) III. (18) IV. (34) v. (32) VI. (15) VII. (15) VIII. (20) IX. (15) TOTAL (210 Read each question carefitlly in its entirety. Check immediately for 18 (including this cover) dijferent, non-blank pages in this document. Chemistry 322bL Final Examination page 2 August 11, 2008 I. (26 pts) Provide names for the following structures, or structures for the following names, as appropriate. Either IUPAC or common names are acceptable. Don’t forget stereochemistry. . () ° . t * < 9‘ a ('LOH .. Ml ro b V120 LC CidJ CHI] (25' [’4‘ v 2 I” Q!» -3- {r 0 (b) g\ /CH2 ,CHa 2- (§>‘3- hat/l Q +— (c) W (I? E _ Q ‘ ~ r M - CH3\ ,/c\ ,C\ . I (EH NH-CHa - - -— O \ H H N are;— (d) DMSO (e) DMF (2> (f) THF Q 5 <2> \\ (He (‘3 l / \ <2> man CH3 MIC—Nst {J (g) Name the following molecule as a derivative of allose. Be sure to specify all the relevant information including ring size, anomeric configuration, absolute configuration, etc. (The molecule’s specific rotation is clockwise.) H OEt OH H OH HO 0 H OH = OCHch3 H OH OH H é_b_ / g H I \ Chemistry 322bL Final Examination page 3 August 11, 2008 $3 11. (3ipts) (a) Complete the following partial structures so as to draw all reasonable resonance structures to complete a good representation for the indicated cation. There may be more partial structures than you need. (Don’t forget the charge.) 0" H2 CH2 CH2 CH2 ,6 CI 6; ‘ Cl ‘ CI ' CI <-—-> <——> <——> F F F F OCH3 OCH3 ' OCH3 OCH3 <S > CH2‘ I ®CH2 CH2 , . ‘ Cl ‘ / I63 CI <——> H O Mo+ F I F F named (gyms OCH3 OCH3 bug” O (b) Circle all of the structures at the right that @present valid 1: molecular orbitals (bonding or antibonding) for 1,3-butadiene. (Ignore the re a we in; of the contributing atomic orbitals. Light and dark lobes represent the “+” and “-—” algebraic sign (not charge) of the atomic wave functions.) V V? H 9H2 ‘ H‘ l ‘ H; H H; flaw/s Qwfirs (Jammy a a a s a (I’m) ( (c) Methyl iodide exhibits an absorption in its UV spectrum at ca. 250 nm. What kind of transition must this be? (Hint: the C-1 bond in CH31 is unusually weak.) < 4 > n—m“ n—>1t* n—>n* o—->G* n—m" Chemistry 322bL Final Examination page 4 August 11, 2008 (e) Label each of the following molecules as aromatic, gag-aromatic or m-aromatic, as appropriate. CH3 l ©Q©éu Qrowaim a L mm Oern ansin )c (SO H(ii) EH" H H arm “C mm 'C {Bram \c (f) The compound above at the left is [18]-annulene. Would you expect the 1H NMR resonance for each indicated hydrogen to be at unusually high chemical shift, 1212 chemical shifi, or at normal < chemical shifi?‘ (0.111134%.— (ii)_lfla)____ Chemistry 322bL Final Examination page 5 August 11, 2008 (i) Give the pK. of the following acids (1 units). IS-IL [(0 l0 5 26’ (+) OH / N/ < \ I > H30 H20 CH3CH20H \ ' CH3-CEC—H -2 H E E (g 8 cozH CH3/ ‘CH; ‘03 CH; ‘oet CH3/ ‘CH3 H Qg H 520 S” (j) Circle the most acidic molecule below. @c Chemistry 322bL Final Examination August 11, 2008 page 6 III. (18 pts) For the following answers, the more words written, the lower the grade. What is the 1° structure of a protein? W AA’; M 5% i What is the 2° structure of a protein? LOCOQ 2-D Mn: Nehelix) flrflfiwfi) C619) mmlovn What is the 4° structure of a protein? ‘ ‘ ‘ $re£fiam0£W PPO‘lQM/lm ,0 mm) [Ll/coax M (Qd/Zfi What species binds most tightly to an enzyme? "Wansl-l-‘on 54%}? In sequencing a polypeptide, what information does use of the Sanger reagent provide? H4 N—ferm'wmo aVHlVID m:le What information does use of carboxypeptidase yield? ‘ll‘i C‘fat‘mfwac amino («1&26/ What does the Edman degradation tell you? Note/m W250 A A) Mipea'fwl twang The Edman procedure can be used to sequence small polypeptides, routinely up to 20 AA lon . Why can carboxypeptidase generally ident' nly e first AA? ~ {I}, Cleaned — 1—} Aoesflfil I551: ' AA Cowl—m tree. down gamma W Own rCth'M W W . Chemistry 322bL Final Examination page 7 August 11, 2008 IV. (34 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 Q , mechanism. “Workup” means treatment with water, dilute aqueous acid, or dilute base as /r appropriate to generate the product shown, followed by isolation of the product by appropriate <[>Q/' means. (Note that “No Reaction” is always a possible answer.) 5mm We!) MeO— H Me2304 H0 H (excess) _———‘-‘_——> H OH NaOH. H20 H OH CH20 (b) H— OH Ho H PhNHNH2 (excess) HO H ——--————-——> H OH H HzOH H30”) W H + mo H Chemistry 322bL Final Examination page 8 August 11, 2008 (d) IS! Q! (+) _ +3 H} NH3—9H-CO—NH—9H—CO-NH—CH2—Cog) H N/C\N ’qg If)le guflc'é 0 CH) CHZ . \A/\ + ’ a ‘ O NH \ 1) Ph—N:C:S, pH ~9 Q 3 96 Gog ) 2) anhydrous HCI. CH3N02 3 . 3) H30“). A o 1) KCN, HOAc (4 OH H OH 2) Ba(OH)2, H20” u 0 H 3) H o(+) H OH 4‘ H OH H OH 3 4) Nang. H20, pH ~4 H OH H OH CHTOH (show both products) 4 QJ—hd-J (f) F J‘H‘CHQWWW N02 ‘ _ N01 H o / ©/ + (+gll-ia-Cl-I2-(POWPePflde) ———I:—B—> Q N02 p (g) Ho— H A020 Ho H pyridine OH 0 °c OH CH20 (h) C C 0/,0 1equiv Brz Ha H2 \OH P(catalytic) (dark) Chemistry 322bL Final Examination page 9 August 11, 2008 (0 H0——— H CH30H HO H solvent catalytic 0” st04 OH H20 (3 H 25' ° ° _____.__. CH 5-K) + CHa/lLOJkCH3 w» (k) __ 9H3 AIC|3 CHIN} Q + CH3'9‘CH2_CI "“—‘-" L‘Q/ large CH3 excess (1) , 9H \CH3 CH30\C/O/ 1) NaBH4, MeOH H 2) workup Q 0 (H!) CH3\ CH3 E? . V CHa~C-(|3H-CH2'CH;5 CHa‘CH-CISH-CHTCHa CH3 NQ CH3 Jm QHaOH EHH Dr malt! Chemistry 322bL Final Examination page 10 August 11, 2008 V. (32 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. “0 XS 0” 0‘90”) 0*26 Q {-9 I N0 75%“ li/U + Q)” 2— N 3— N01 The two most commonly employed syntheses of racemic amino acids are the Strecker synthesis and the acetamidomalonic ester synthesis. (b) Show how you would use the Strecker synthesis to prepare tyrosine fi'orn p-methoxy-Z- {J phenylethanol and any other needed reagents. (Recall, the Strecker step uses NH4Cl and KCN.) 4f? CV0 CH2CH20H COZ(—) M Q (+) 3; @— f : ........... up NH - H-CHz CH C) 1 air; out]. 9431‘” <\ (+3 (7” MHz (“Hg (Q 0C”; 1 CH2 _C‘H, C N 9442244034 Lisleps HLO Chemistry 322bL Final Examination page 11 August 11, 2008 (c) Show how to use the acetamidomalonic ester synthesis to prepare glutamic acid using appropriate starting materials. 6 ( 3 0‘ H A twig—cow , cHZCHzcozH ——CO& FLCHzcozH . ' <C3 C) H ‘ b Mam-l) H10, n l Wow—cue; Eé)1 23 H 0+ . . (3 Eé— 5 M Jnc. NQOEt 8 la = 0" Lfl—T’» 0438M” $‘(O'L‘t ( (9 m HCI CH1=CH CONE CHM; C0; '55 $4» " 5W5 (d) Provide a good synthesis (i. e., minimum number of steps, good yields, etc.) for the dipeptide NAla- Valc from the individual amino acids. Show the molecular structure of any group or reagent at least once. Thereafter you may use an abbreviation if you wish. Be as specific as you can regarding reagents and conditions. Show the product fiom each important step of your synthesis <+> _ <+> _ Ala = NHa-clH—coé’ Val= NHa—CIFH-C02U @0410” “H3, cu- EmocHng -————-—-—>' 54 s CH3 9‘“ 14st JP 5 a? , CH3 Cfi’ L F ><°‘I’°7I’OX c, to “30% «30 M t :5un may C\ {n 2" C’ ICI" '— 1' ‘ Q_\§9\..&-Nu-c\u m. as .1 r CH} C OJCH“¢ Q H 2 6‘04: Hz.) (.3 CH4) CHme’z Nl—lg éHr’C NH— ICH’COf‘) 9: H 87:“ in HDAC A Chemistry 322bL Final Examination page 12 August 11, 2008 VI. '(15 pts) (a) D-Preposterose, A below, is an aldohexose. All but one of the stereocenters are established by the data shown below, particularly by the observations that compound E is optically inactive, while B and G (next page) are optically active. Show each structure 3-6 with only the con rational in ormation that ou can conclude om its r0 rties and the recedin structures. Then complete the answer as directed on the next page. Show all structures in their non-cyclic Fischer projection. Note: Even if you cannot establish the configurations, partial credit will be given for partial structures if they are sufiicient to demonstrate that you know what the chemical transformations are. it V" max Brz H26 + —’—-> i H OH CHZOH OH D-preposterose, A €0ng HN03 H20, A COXU OH C) l E, optically inactive Colu B, optically active Chemistry 322bL Final Examination page 13 August 1 l , 2008 And, 1) Brz, H20 D———————-————> 2) H202. Fe3“, A The final piece of information needed to establish the configuration of D-preposterose is that no other aldohexose when oxidized with nitric acid ives the same roduct as pre osterose. C 2 fl» A JV) 41$ 0 Complete the structure f D—preposterOse below and in one sentence explain your choice of configuration of the last chirality center. Chemistry 322bL Final Examination page 14 August 11, 2008 VII. (15 pts) Isomaltose is a disaccharide that can be obtained from enzymatic hydrolysis of amylopectin. Deduce the structure of isomaltose 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) Hydrolysis of one mole of isomaltose by aqueous acid or by an a-glucosidase gives two moles of D-glucose. 2) Isomaltose gives a positive reaction with Tollins’ reagent or Fehling’s solution. It forms a phenyl ‘ osazone when treated with phenyl hydrazine. It mutarotates. 3) Isomaltose is oxidized by bromine water to isomaltonic acid. Methylation of isomaltonic acid with MestdNaOH followed by acid hydrolysis yields 2,3,4,6-tetra-0—methyl-D—glucose and 2,3,4,5-tetra-0-methyl-D-gluconic acid. 4) Exhaustive methylation of isomaltose itself followed by acid hydrolysis gives 2,3 ,4,6-tetra-0- methyl—D—glucose and 2,3 ,4-tri-0-methyl-D-glucose. The structure of isomaltose is: ' . 0'31le 0 QCQ’WR glucose ‘——OVLQ glwose Sm cavaluc \ v ‘ ucosf'dxk 2) swim W M WH(“°“‘3' » a) (mm alum/\giya W ' om nu<>\ /E OH m0\/m\o\cozH Chemistry 322bL Final Examination page 15 August 11, 2008 VIII. (20 pts) (3) Very briefly, what is the difference between specific acid-base catalysis and general acid-base catalysis? Se ' ‘ roion £mn$§€r occurs begicrc or “p3 iceliigduflgom loo/v6 Chan/13,24 —— via W 0»qu 0'“ QUAD 0060., \‘w héau Gaul/MD mien £mhs§ar Ocruvs M73 3 033M boni‘nfi COWKQQA so Vain W 0M 3:? ~ [0 Immflxmwfl fl Mich ’ w/wfim a P How do enzymes use general acid—base catalysis to speed up their catalytic reactions? . I W Lona/.1 mum Hm? MW Ma ' ' FRBED) fifin) . a A 0A (it We :2 “has P V 0 W W be - (b) Aldol es comprise a class of enzymes that interconvert fructose 1,6-bisphosphate with acetone phosphate and glyceraldehyde 3-phosphate, as shown in the set of schemes on the next page. In the reverse direction this is an aldol reaction, and in the forward a “retro”-aldol. In vivo, the reaction is driven in the retro direction by rapid further metabolism of the two product fragments. “Class I” aldolases use lysine and aspartic acid residues as the catalytic functional groups in the active site, in addition to numerous residues for substrate binding. Scheme A below represents the enzyme and its initially bound substrate, and scheme E is the enzyme and the product fragments. Schemes B, C, and D represent intermediate stages of the catalytic cycle. i) Complete all structures in schemes B, C, and D below, being sure to include all atoms and charges. ii) Draw curved arrows in scheme B to show the “flow of electrons” in the transformation from B to C. iii) Draw curved arrows in scheme C to show the “flow of electrons” in the transformation from C to D. iv) Comment briefly but specifically on which parts of this mechanistic scheme are good examples of general acid catalysis and/or of general base catalysis. Chemistry 322bL Final Examination page 16 August 11, 2008 CH20P032' | a £5 C =Q‘(CH2)4-LYS Hogcsz H (EH20P032‘ HID-61H}??? B <|3=o NHz-(CH2)4‘LYS (229) HCIZ-O—H \C—CHz-Asp Ho—cle {/V CH20PO32‘ o” A HC—OH I H—O\ H(l3—OH 2 /C—CH2—Asp (33) \ CH20PO3 ‘ 0/ CH 0,3032- l (Ir-44‘ -(C H2)4-Lys HO—Ckfm: C + H-foi H<|3=0 C—CHz-Asp HCI3—OH o” 2- (EHzopoaL CH20PO3 9:0 NHz-(CH2)4-LYS CHZOH + _ E CH20PO32’ H 0\ g.) H(|3=Q //C —C Hz-ASP ('3 = “((C I"'2)4"|-Ys H(|3_OH O CH20H HC=O \ Chemistry 322bL Final Examination page 17 August 11, 2008 ’ IX. (15 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 fonnalism” that you use. (a) Four intermediates. 0 CH? W31 LEO O Chemistry 322bL Final Examination page 18 August 11, 2008 (b) Five intermediates ...
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This note was uploaded on 01/22/2012 for the course CHEM 322B taught by Professor Jung during the Spring '08 term at USC.

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Final Exam - Summer 08 - Chemistry 322bL Name Emil CBC/{42F...

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