Final Key - Final Examination Chemistry 262 Organic...

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Unformatted text preview: Final Examination Chemistry 262, Organic Chemistry 2 ' Summer 2011 August 18, 2011 Chemistry 262 Academic integrity Policy: Students are expected to strictly adhere to Washington University’s academic integrity policy. Any violation of this policy including but not limited to cheating on examinations or re-grade requests will be referred to Washington University’s Committee on Academic integrity. if the committee finds that a student has violated the academic integrity policy, then the penalty will be without exception automatic failure of the course. Examination Guidelines This examination is an in class examination which is closed note and closed book. You are not allowed to collaborate or interact with other students while taking this exam. Only black pen or pencil should be used when taking the exam. Only course approved non-graphing, non-programmable calculators can be used. Molecular models may be used (it built prior to the exam). Problems must be completed in the space provided. No credit will be given for work done on the back of exam pages. if there seems to be insufficient space, an extra page is provided at the end of the exam. Please indicate if there is work on that page that needs to be graded. Neatness and iegibility are required to obtain full credit. Should an answer not be legible or decipherabie, it is the instructor's prerogative to assign zero points for an illegible/unreadable answer. For answers requiring calculations or logic, points will be awarded based both upon the answer and the work shown. i acknowledge having read, and agree to abide by the Washington University Academic integrity Policy, the Chemistry 261 academic integrity policy, and the examination guidelines described above. Furthermore, i acknowledge that failure to follow these policies and guidelines as described by Washington University’s Committee on Academic integrity will result in failure of the course. Signature: Date: Print Name: Student iD: Page i t QUESTION 1: REACTIONS Determine the product(s) of the following reactions, please draw all stereochemical possibilities. If you believe that no reaction will occur, please list “NR” in place of the product [20 points] 0 " ’ o/ O A1013 Zn(Hg) 0 (33k 0 4- ® HCl \ N NaN02 H20 A 1) UAIH4 M 2) H2O/H+ 0 ° W ’ HO O 0 1)EtO—, EtOH 0 Cl WAG/“Y Y:th 0 gal— NaZCO3 2) H+/H20 0 1)EtMgBr, Etzo fij 2) H+IH20 \ 1)EtMgBr, EtZO o 0.1 equiv. Cul /\ W5 2) H+IH2O Page l 2 QUESTlON 2: TRANSFORMATIONS Based upon the reactants and the products shown, fill in the reagents and conditions necessary to accomplish the following synthetic conversions. it is possible that one arrow may correspond to more than one step (i.e. reaction and aqueous work up), but does not represent more than 2 unique reactions [20 points] 0/ 5: “3° ° (3 N93 (1) 9 CH} 0H' t) Li Al H4 fiOH 2') H+/ HLO HO OH l) B“; p/‘oei Z +- H 4N. yam... H ) H [H20 caps n. O o l) EH3 OH H 2.)!“ szo O o «3 OH CL 0 g) “A HJLH l) SAW; V HJV P H/u\/ was“ 0344‘ ‘7‘) N/Hzo H CHLC‘L {*4 flaw“?- 80% W0 t) D\9>AL \OJO We 7.) Ht mus O O O 6 Own *1} Ohm Not on; O O \\ LDA \ij 1) 9P3:— U 0 OMCDGQ Md)” 2 Cl o-vabasos.’ Ma“ \6 D.%L$LDA are 0, amt— Page i 3 QUESTION 3: ELECTROPHlLlC AROMATlC SUBSTITUTlON [13 points total] A) Draw the mechanism for the nitration of benzene shown below [6 points] © HNO3 ONOZ H2804 O HtO “ o o é N n @o/@\._0_7‘H H90~2~on #9 67/034403)”, Z 6)ng U 3 :4 “ Q 0 o Hrteesa O \\ .__.,——> GEN u / \ f.) N 90 b 60’ l §r H G) / l? BREE: eo_fi_09 D‘Hzo O B) Based upon the reactants and the products shown, fill in the reagents and conditions necessary to accomplish the reaction shown below. Please write in reagents over the arrow and be sure to provide work-up steps if necessary. [3 points] ©/NOZ 0F: ~or- SA,H<:\ ©/NH2 2) Na HCO} <1! W'Nafliks aci‘é tam: mix/92 enilimwoéMw Page i 4 QUESTION 3: ELECTROPHILIC AROMATIC SUBSTITUTiON [10 points total] cont. C) Amine groups are typically considered to be on‘ho-para directors, but under the conditions shown below, only the meta product was obtained. in 2 or 3 sentences, explain why the meta product was observed and who and para were not observed, an illustration may also be used to support your explanation. [4 points] 1) Gig, AlCl3 (excess) NH2 NH2 0 2) H20, NaHCO3 Cl - m Aid} is a Lewis acic‘Le’ acupi-cv) , qus: Aida veach N/ OV\ +0 G;Vl a PcngVQQj chafi<4 G) ®/Alcl3 MN 3 Posi‘HVLQb chevJJzé. misc/63w [ammonium/x seUc) /' ‘s a Wu. :1 cl; Hvx Q | t VLL j Gravy QUESTION 4: SPECTROSCOPY [9 points] _ For each pair of molecules below, explain in 2 sentences or less how the spectroscopic method indicated would allow for the differentiation of the two molecules , \Ws 951,0 r—“L‘fi A) Mass Spectrometry , A Wm H Show a“ M__ ‘8 Haj My as a OH 0/ N , madw {foam-$3 E woulémo-‘r‘ A s - 2 Mt'OM-i Show M-ls 9. wen es Maw Mass-.5 or ice: a¥ 4S B) lR Spectroscopy O O ' S, Wouié Mcvt a Q=o Q. “‘HLIO UM" AO/ AN/ C H ' g woutd irléV‘ a CL=O € “[950 w‘l ._ Q L \Ncwt‘A 9‘50 V‘th aMN-‘H s’rvci'ck new 3:400 m“‘ C) 1H NMR Spectroscopy H H ph\)\J/CH3 [3th ° V‘whmé on atsz. wwflé \Aevc AeiE—wa—i‘ \ \ . H I ‘ CH3 A—Vah/JS Lowfins opus-tavxk) hams A: HE Page i 5 QUESTION 5: SPECTROSCOPY [10 points total] The spectra on the following pages are from only one of the molecules shown below: 0 ob“ one“ or“ Part 1: Based upon what you know about spectroscopy, circle the molecule above that correlates best with the spectra provided. Only circle one answer. Also, the remainder of this page is left blank for you to show work. Please indicate how you determined the identity of the unknown molecule; no points will be given for an answer in the absence of work [5 points] Part 2: Once you have identified the unknown molecule, assign the signals in the 1H NMR spectrum to the appropriate protons in the molecule. [5 points] SHOW WORK IN THIS BOX ' 1K shows 1'- OH Kn”? I75 coo-[r a land acr'J “(raw H———> 910+ or?» 0 [fl '4 Show; L‘K. sub WI “04' a No SaLak e, Cgtospw a“ ‘H‘NMKH—a no alJLhJu H—e my (a 0 Mass Spa; shows mfiov #1“ IS 9'" £93505: ML 5’5 lt'lacifl E [as Mass Spec dye—E VB} Sim».- \css 05; \‘3 H—> H10 mvta {35(514—9 1—0” M 'Ku'vts @W.» 2., we Mafia ,5 ® hm“: (‘Z\4’1 L your) in a‘km VGNV‘ («AVG-brunt» l—v cwz<u3 ‘ ‘H“NP\\Z so ® Cm~§iwms 3 ® Page | 6 QUESTION 5: SPECTROSCOPY [10 points total] cont. l0!) 5» w + J B rm -v r—‘I \-— r 1 W T r——-—1—-—-—1 -——v——-—T wr— «— M-r- w {390 3009 2009‘ 1599 £000 5E9 HRY’EHUHE E!“ -II T! HHSNI TTRKCEI 'I.l 100 107 80 O"! O 122 Relative Intensity 11:. O 20 10 20 3O 4O 50 60 70 80 80 100 1 10 120 Page | 7 QUESTION 5: SPECTROSCOPY [10 points total] cont. Page I 8 QUESTION 6: KETONES AND ALDEHYDES [12 points total] A) Draw the mechanism for the formation of the dithiane from the aldehyde and dithiol shown below [7 points] 0 HMS KW JL 8 H S S H H H+ H><H L“ H—‘A Jk "—6 /ll 6) —-.-—> H t. H V‘A H (+3 921° (\1 ————-> ‘0’“ m K‘ sat/o. 4-9 “we 51 we HH 6AAsu u \-l H><H B) This dithiane can undergo a series of useful reactions/transformatlons to yield aldehydes and ketones. Fill in the boxes below with the products resulting from each step [5 points] Page i 9 QUESTION 7: WOLFF-KISHER REDUCTION [22 points total] The Wolff-Kishner reduction (shown below) was used as a final step in the synthesis of methyl kaur-tB—en-t9~oate, an interesting natural product that can act as an ATPase inhibitor. A) Draw the mechanism for the the first step in the Wolff-Kishner Reduction, the acidvcatalyzed hydrazone formation. [6 points] O The starting ketone can be abbreviated as: R1/UW/ R3 /‘ R2 N“: K H ~ A H'“A N“ 1 \ F. K: 3 —————-9 R‘x‘g} a / R 2. ‘12 ‘ ‘2‘ Rt ‘2'; 0K {SI mg stops an iru/wue his ~+ PH //~-.¢ L. H NHZ HL0 49 “ 'Nu \ ‘5 /‘ Mvs+ ‘ K! + H" A \ a . g1 vuM vc ‘22 H B) Hydrazone formation is a series of equilibrium steps, what drives or is needed to drive the equilibrium of this reaction, please explain in 2 sentences or less. [2 points] Hzo'is lost in ‘HM- 2"“ ’r-v \as’c SB? 8’ WWW“ be “Moved er boilzé 0% +1) Av‘H/K ‘HNL exui‘ukrivxng Page | 10 QUESTION 7: WOLFF-KISHER REDUCTION [22 points total] cont. C) Draw the mechanism for the second step in the Wolff-Kishner reduction, remember this step occurs under basic conditions [6 points] l4 H ‘ N"{7\ii/2>on N/ r319 “4,49 (’N‘Q Q U N 1" on u R —————-9 six ...__) ,l 9- R1 [L1, kph?" H ‘11 i.) —-o H U [1 9 fl A = 2.. 7 2 ____Z_a " e 9. ‘ —-———> ‘ \2‘ / / 2 R, g H a, l3} l-l inure/Sikh ‘12, ‘21 QM! “1 D) This reaction is also predominately a series of equilibrium steps, what drives or is needed to drive this reaction, please explain in 2 sentences or less. [2 points] ° l s \oss cf- N1 is 'iving/wsilolgji-ikloss/mmqu «Ira pvoéuc’r Aim/cs Hut 6%. - PYO—h“ab‘ow as; Cavbavu'ow twtas’l- aim? has a has; Kw" «hit/(:7 Farm. 9V4 mo= it, Pm t, wsz 50 H 34% :103‘5 W wit—v. 3:14 semng E) The second step of the Wolff-Kishner Reduction is performed under extremely basic conditions, which can result in a side reaction. . What other functional group on the molecule is involved in the side reaction? Draw the side reaction and the product that would form as a result of the basic reaction conditions. [6 points] . W9. Qs+w can Vggcfi- /\gg Sam-m mi :4 \‘L/\/ s V : &\ My Page l ti QUESTION 8: ACETO-ACETATE SYNTHESIS [14 points total] A) . Fill in the boxes below with the major organic products resulting from each step [8 points] O _ 2 i 1) LDA, THF i/‘K OH 1) MeO , MeOH OMe g / 2) H+/H20 2) BrA/ KOH O O O "k “30+ wk 09 ‘V/// A \,./ 7-: B) Provide the mechanism for the last reaction in the series; be sure to include all products formed as a function of this reaction. [6 points} C°2_ O O H \ .u ’vu ® (9 0 O '0 l-‘r " 092 )Kl/L 09A”sz "3 wise “‘4’ Egg v QGQHK : OHL ____..___9 H C) 21% H ; Page | 12 QUESTION 9: ENOLATES, MICHAEL ADDITION, ROBBINSON ANNULATION [16 points total] A) The enolate shown below can be formed via a Michael addition to the enone, fill in the reagent necessary to accomplish the conversion. [4 points] 06) Q l) L} Avaxl w (GHQZCML: W CH3 B) The enolate above can be used directly for a Robbinson Annulation. Starting with the enolate and methyl vinyl ketone (shown below), draw a mechanism to show how the indicated product forms.[10 points] 06 O O é MeOH,KOH 1 H30 : CH3 P5 Mw—H< c3 W0 W O o (90 \7‘ / 2 1/“ L’ / { 0 ¢ an; O 9L9” 600*; C) The aldol condensation, which is the second step in the Robbinson annulations, is a series of equilibrium steps, what is the driving force of this equilibrium, please explain in 2 sentences or less. [2 points] ‘ <5 ’ QQJMMa‘F‘M b “EDVM ‘Hflv CMOWL (whtdxi‘s STQHL é“"\“ c’“\.)v33k°“) fvcvvée: +‘Mfi. .EOVULI 4:0“ 4%,. Vg’ecfk‘fov Page i 13 QUESTION 10: THE WITTlG REACTION [14 points] A) Draw the mechanism for the formation of the ylide shown below: [4 points] JV 1) Ph3P, THF M Br 2) LDA, THF “‘3? \3V ——————;r e I? .. 9 l—I 3‘" s L W {/kAPPl/ss] N YNY L._~v._._—_l LDI‘N B) Draw the mechanism and the resulting product for reaction of the ylide generated above with benzaldehyde. Be sure to indicate the stereochemistry of the resulting product [8 points] 0 JV? + —-—-——-———> PPh3 H 6) m .._. Win 3 H F“ H/\_—J~\\ F“ H W F“ >~-—z H C) Assuming all other conditions were the same, draw the product that would result from the Wittig Reaction above if NaH were used in place of LDA in the generation of the ylide. [2 points] f\ PM utilises mil Mama \/ \N\n{c\/\ \aac‘s \m SWcocM'lst’U “1'ka pm (LAC/3" Page ) 14 BONUS QUESTIONS BONUS QUESTION 1: MECHANISM [4 points] Provide the mechanism for the Curtius rearrangement shown below: @696 1) z 2 Cl N N N NH2 0 2) NaOH/HZO 60 \/ g N1. ~———> F‘s/fight m~ v ’17 WNW—9° —» @N=§/7>e 60 H—DQJ OAK) \bt-‘r BONUS QUESTION 2: KE$HA [1 point] Provide my favorite song lyrics from my favorite Ke$ha song. Page 1 15 EXTRA PAGE Page |' 16 RANDOM STUFF THAT MIGHT BE USEFUL x l8 VIIIA ‘ I 2 Perlodlc Table of Elements He 13 14 1' 16 17 111A IVA VDA VIA VIIA 40026 I 6 7 8 9 10 C N 0 F Ne 2.011 14.007 15999 18.998 20.180 15 16‘ 17 1.8 P S C! Ar 6 7 VIE VHB 9 VTIIB -_ ., I _ , 3 4 5 22.9’90 24.305 “"3 1V“ "B 519:; >207" 21‘ 30.974 32.066 35.453 39.948 34 ‘ 35 36 Se Br Kr 78.96 79.904 83.80, 53 54 I Xe 1269013129 6 8 EQUATIONS AG = -RTln(Keq) Keq = e-AG/RT CONSTANTS R = 8.314 J/mol K R = 1.985 x 103 kcal/mol K R = 0.08207 L atm/mo! K Page 1 17 ...
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