322bsu09_e3_key

322bsu09_e3_key - Chemistry 322bL Name :9 EZV‘ \S I Basic...

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Unformatted text preview: Chemistry 322bL Name :9 EZV‘ \S I Basic Organic Chemistry July 27, 2009 TA EXAMINATION 3 Answer the following questions in the space provided. Please organize make your answer as legible as possible. Ifwe cannot read your answer, it credit. Please remember that C-C-C-C without hydrogens and “stick” structural repre tations will be given N0 credit (except for rings only). You may use the backs of pages for scratch paper. I. (12) 11. (08) 77 A) C. m @0: Q IV. (24) V. (20) VI. (10) VII. (10) TOTAL (100) Read each question carefully in its entirety. Check immediately fbr 10 (including this cover) dijferent, non-blank pages in this document. Chemistry 322bL Examination 3 page 2 July 27, 2009 I. (12 pts) Provide names for the following structures, or structures for the following names, as appropriate. Either IUPAC or common names are acceptable. Be sure to specify stereochemistry if it is shown. (a) / mifimfiocmm l E- - Quiet/to ’in \9)? H (b)H o cob Ok I I I <3? /CH2 "" I I 3 CH3 (0) CH;E\O/E\CH3 (c) potassium a-acetyl-B-bromopropionate (d) benzyl benzoate C) ’6') _// 426% @r—CHZ‘CU—8~09 HG) ta—ocfawtsif O4E‘CH} fwan dL 4-4. t7 CH» II. (8 pts) Show all reasonable resonance contributors to the most stable anion that would result from deprotonation of the following molecule. Partial structures are provided for your convenience. You may or may not need all of them. 0 O 09 O _ l / I ‘OH ——> \ H \ ‘ ’ \ Chemistry 322bL Examination 3 page 3 July 27, 2009 III. (16 pts) Please circle the item that best answers the question posed, or fill in the blank, as appropriate. (a) Give the pK. of the following acids (:tl units). <3? 0H 0 / (3/14 002H :7 H3 <7 o o Jliihfiiflii .2}: (b) Which one of the following molecules does NOT exhibit a positive iodoform test? m Q22. (b) The pH of a dilute aqueous solution of C1CH2C02H (pK. = 2.9) is adjusted to the value where the carboxylic acid is half deprotonated. The approximate pH of the solution is 1 2®4 5 6 7 8 9 10 ll 12 13 (i) Place an “S” in the blank of the strongest acid and a “W” in the blank of the weakest acid. Be sure to mark only two spaces. (More than two marks invalidates all answers.) (2 CH3 C01:2 C02:2 C02H F/gCOgH QCOzHC COzH > of? E TEL. __ CL... 3?. /’ (c) Place an “F” in the blank of the molecule that undergoes the fastest nucleophilic addition to the acyl carbon and an “S” in the blank of the slowest attack. Be sure to mark only two spaces. (More than two marks invalidates all answers.) Chemistry 322bL Examination 3 page 4 July 27, 2009 ((1) Which molecule has the highest boiling point? 0 O u (EH3 H’B\CH2’CH2~CH3 Cchw’CHa CH3’CI‘LCH2’OH <1 > 0 CH3 CH3 II I CH3’C\CH2’CH3 CH3‘O’CH\CH3 CHg’éH‘CHz’CHii (e) Which of the following molecules has the largest ban'ier to rotation around the bond indicated by the heavy line? Chemistry 322M. Enmineflon 3 page 5 My 27, 2009- (24 pts) GiVe the main organic productfs) fix the following reaction. er‘pum'de the needed reagents and conditions for the transfonnation shown, as appropriate. More than one step may be required for a given compound. Be sure to note stereochemistry and/or regiochemistry wherever relevant. You do M need to balance the equation, show byproducts, or show any mechanisms. (Note that “No reaction” is always a possible answer.) 2 QM e.) 9 300°C 9 HO-CCHZCHzC-OH —-————> \ \ (e) O (1) add ketone to O i I CH23I‘ sli ht ex of (2) W C awn-PCS? G CHECHJC H ‘ C ‘CHJ. Z CHacHz—cle/ \CH3 ' CH3 THF. -78 °c (3) “20 W°"‘“p CH //\‘ 3 Q i he . (\{goadilnons > Et“C" («~59») CH: 0 Chemistry 322bL Examination 3 page 6 July 27, 2009 2 54C A O catalytic l / 0 ('3' NaOEt &\ M j + CHFCH/ \CH3 lg} C HOEt _ ‘ - (h) K @C\CH:CHCH3 (anhydrous) E/ C I C H O (‘a M thr 04 7’72 %. 041-” 7 ‘6 :0 ) '6 m 0 1 1 /doH <:©,3\CH3 “$3213:ng H20 <:© 2) H30“ ( + CH I; B G) L 4 (PI 3 catalytic NaOEt (I 3 CWC‘CI-ECHZ‘CI-ECchI-E ‘CHa EtOH CH} 0V -‘ O Chemistry 322bL Examination 3 page 7 2 July 27, 2009 6 def ‘ K (k) 0 if: M m 2,‘ ea a a -‘ + CHa/C\O/C\CH3 _’ Q N_ H/N \\q/ C“; C02” 2)1§NH3 O\/\/CgN / f . m 3>Aczofl \A‘J M“O “[7 C—wflb’t) V. (20 pts) Provide a reasonable synthesis (i.e., minimum number of steps, good yields, good stereoselectivity, good regiochemistry, etc.) for the molecules specified below from the indicated starting materials and any other needed organic or inorganic reagents. Be as specific as you can regarding reagents and conditions. Show the product formed from each important step of your synthesis. Be sure to indicate if a step results in formation of an ortho-para isomer mixture, but assume that such mixtures are readily separated. You do not need to show any mechanisms. @ H (a) +©—CH2~C/\/: ©on and CB —---> QCHg-CH-(§—N::| NaDE'f ED (Caidia'i’l‘ ‘ <g 55-04: C-(EiH £15 #6 I ¢0142C1+~C\U Od/Carboh 0 V [QWnOLl gong on 8H noulgurogH Chemistry 322“. July 27, 2009 Examination 3 (b) In the following if you get stuck getting to any intermediate, then just jump to it and continue. N jam Q (l ‘ cs ‘5 I .360 i / , * 7’ l (gestalt ~3- 9;: L Q? T commit ¢ \ / \ 97“; A'CN S , (5r 1. ms W m VI. (10 pts) (a) Provide a detailed mechanism for the following transformation. There are four (4) generally accepted intermediates in this reaction, so only four will be graded. Also, show in each box the arrows appropriate to rationalize the next step. The quality of the electron pushing will contribute to the grade. Chemistry 322bL Examination 3 page 9 July27,2009 1 do 0 {teen} 0 each CH1 NaOCH3 H <———— + H20 CH30H 1 O VII. (10 pts) (a) Basic hydrolysis of an ester is a pamdigm for nucleophilic acyl substitution reactions. It has been debated whether the mechanisms is a direct one-step (concerted) substitution similar to an SN2 (~SN2): ~S "2 .9 o t i? CHa/C\OCH3 + HOH ——* ens/('3'; 6 —’ CHa/C\OH +HOCH3 ‘bHSH ¢fast Trgrgtigon CH3C02H + HOCH3 Chemistry 322bL Enmlnation 3 page 10 July 27, 2009 or whether it is a two-step substitution proceeding through a tetrahedral intermediate (let’s call this mechanism AGNZ; in the first two steps below, proton transfer steps are not shown explicitly): A 2 _ °" 3 H20 fl)” OH (I? /C\ H “I’ C» ——--> /C\ H CH3 0cm + OH <— CHg’ goon-I3 .6... CH3 OH + OCH3 OH fast Tetrahedral H “WWW CH3002 + HOCH3 Myron Bender at Northwestern University published the following experiment in 1951. This experiment involves the partial hydrolysis of an acyl-oxygen-labeled ester with analysis of the isotopic content in the recovered starting material. No *0 o 4:. CHg—C// + 0H('L___'123__.. CHa—c” + CHa—c” "b", be“: “M W completion ,, (*3 49 + CH3£%—) + CHa—C~;(—) \o 0 Give a detailed mechanism of the basic hydrolysis that explicitly shows how the label is lost from starting ester. AND 0 State whether this experiment supports the 8N2 or the AcN2 mechanism, and, in the fewest possible words, explain your conclusion. also? a. *QQ 045-8,me :: CH5~C:,-OCH3 + (g4 0” fad- ’4? 7i} (Prom 14* Wins *CPH 04ers“? Tm ...
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322bsu09_e3_key - Chemistry 322bL Name :9 EZV‘ \S I Basic...

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