322af02_e4_key

322af02_e4_key - KEY ~ CHEMISTRY 322aL M Please ’ EXAM...

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Unformatted text preview: KEY ~ CHEMISTRY 322aL M Please ’ EXAM NO. 4 ,. ‘ Print Last Name November 20, 2002 First Name SSN ‘ ‘ TA's Name , Grader . (1) (30) __ Lab Day 8: Time (2) (15) __ _ (3) (15) _.._ __ (4) (20) .— __ (5) (10) __ _ (6) (10) __ __._ (100) first letter of last name I will observe all the rules of Academic Integrity while taking this exam. p 3 Molt/ Chemistry 322aL/325aL ~ -2- Name Exam No. 4 (1) (30) Complete the chemical reactions below by providing the organic product or products (as requested) within each box. You do not need to show ‘ ' byproducts of the reactions or any mechanisms. Provide stereochemical details in the products wherever they are important. "Workup‘ means adding water I and bringing the solution to neutral pH. ‘ $H3 Na+ OCH CH (A) CH3CHCH2CH2CHzBr 2 3 C14 3, ‘ CH3CH20H, heat (HACH QHZQR c a 2 Major product decolorizes cold aqueous KMnO4 solution. C H ._ I 3 (PH .H SO CH Q\+1C_H «C \ (B) CH3CH2CHZQCH3 1—401“: 2 3 Mac or CH3 heat A Lad/u ,0 W1"; L % ‘44,qu (MUM?) Two products a. 6 (1- Label major and minor products. (C) . QCHBrCHZBr m 0% {aflmlu ,orvXcs), Product decolorizes Br2/ CC14 H3 C 3 s (i) conc. H2804 (D) (ii) H20 Product does not decolorize 1 fl 0 {1% W M} Brz/CCI4, but is soluble in cold conc. H2504. . ‘ o H (fr Chemistry 322aL/ 325aL : ‘ -3- Name Exam No. 4 i ' ., (1) Contd. HCECH C C (E) U 2 ‘ excess H2 " “z O b M, 8 ‘ Pt M’ A“! fl’C‘CleflLhr/qit Y ‘I does not deoolorize Brzl CC14. I (F) CyHu. Does not dec orize BrZ/CC14. (I) _C CH KMnO4, HO’, heat 0 isolable product CsHmO Second product is soluble in water and is lost. H3 (i) 0804, pyridine , ('3 w is 5 0L ' "u z o‘g/‘A‘Tad‘knoms PrOuuctis soiublein ‘ 7 cold, conc. H2504. M Mr Chemistry 322aL/325aL 5 .4- Name { Exam No. 4 I (2) (15) Answer the questions below. (A) (3) Provide a detailed structural formula for the compound below inside the box ~ (E)-1-chloro-2-methyl—1-pentene (B) (4) Indicate the number of degrees of unsaturation ("U" number) for each compound below. Place your answer on the line below each structure. H3 1 _ w. M = 3 l 2. (C) (6) How many different proton resonances (signals) would appear in the 1H NMR spectrum of each compound below? Ignore spin-spin interactions. 1 CH3CH2 1 R (FHs \ )‘I ' A CquHOCH2CH3 CH3c1L12cocc1—I3 /C=C\ W CH3 CH3 CH3 H _____’:l:___ __________3 (D) (2) A proton resonance appears at 5 5.0 in an 1H NMR spectrum recorded using a 200 MHz spectrometer. What is the chemical shift of this resonance in Hz relative to tetramethylsilane as a reference signal? Place your answer in the box. .. $7 V? ,_ 307(100 M7" {on " low :1 O o O L“- P—\-% chemical shift in Hz Chemistry 322aL/325aL I -5- . N I ‘u ‘ Exam No. 4 M ' ame ' I ’ (3) (15) On the reagent shelf in your lab, you have, sam les of the diastereom trans- and cis—l-bromo-4-tert-butylcyclohexane. Unfogtunately, the labels his: fallen off. You decrde to use your knowledge of organic chemistry to identify them. You react each sample with sodium ethoxide in ethanol. You observe one sample yields 4-tert-butylcyclohexene ve ra idl , hil th slowly produces this same product. W p y w e e Other sample only (A) (2) In the labeled boxes below draw the lower ener chair confo ‘ ti 1 I. each diastereomer, as requested. Hint: the tert-butyl gap is much lag: 0n for the bromine atom. trans-1—bromo-4-tert-butylcyclohexane cis-1.brom6_4¢ert_buty1cydohexafi e (B) (10) Which diastereomer reacts faster with sodium ethoxide in ethanol? Provide a mechanism that explains why this reaction proceeds smoothly‘with this diastereomer. Be careful to show stereo'chemical details in your structures What favorable stereochemical features in the faster reacting diastereomer I promote a fast reaction with sodium ethoXide? I i I “c fifd‘qs‘lttcow. k—‘BF 8r . F (f) : fH More; W” ———9 .‘l‘ Hem-r5? E+°H ‘ H H H Cbe-‘t- flu. \thmg group; Tm +\\g El mack—tom Must @ be Cam-‘FVFI'P\OJ}\QF _-" or ‘ ___________.. Becorwgc. 04‘ “A 4L0”*“\“\& Qwfiormk‘l—ruu.\ Coven—Ol\ «.4 Ct "d’locsl'l FvCOIl/th‘ Shani-H7 VLue. 4 AAA; 5 , MIL L. RM 5 \ (C)li>3):Br1efly explain why '5 same rea‘clion is so slow with the other diastereomer. \m JrML Jrvqus AQchs‘l‘V-rI—OW‘V‘) («~2er Pm“?! rrl°‘-— chac‘n/ C/bw.r'(‘DTL/\c~+-?°Ms\ ’r‘leus M bVDVU’Kk Q‘ikk‘s‘b "7 ‘“\* TL‘L‘ NQSLUL fine-Pi ——-p¢n—‘ LQWérwafluM \3 om\\/ otvck‘\ab‘< m CkaVF “a? fi/QJS /\\~9. («hyk t‘r-\ouc \ 7r0vi> dfid’il‘ TKVS ComAer_§.*°,k imgrzg SL3 flmg, kwhgy 0‘; ’llfixTS/ 5/‘DLON’KS m net £11561 Chemistry 322aL/325aL i .6- Exam No. 4 I Name » (4) (20) Circle the answer that correctly completes each question or statement - below. (A) The more stable alkenes in the three pairs below are CH3 H3 V - { O (CH3)2C=CH2 CH3CH2CH=CH2 \ //——‘/ A B A B . A B- l (circle answer) AAA ' AAB BAB . BBA (B) The order of acidity (strongest to weakest) of the compounds below is (circle answer) CH3CH2CH3 CH3CE CH CH3CH2QH NH3 1 , 11 , III IV ‘ _ H1>H>I>IV IV>III>H>I (C) Compound A has the molecular formula C21H3402 and does not contain a triple bond. Catalytic hydrogenation yields a compound C21H3302. This information indicates that compound A contains ——_... N C-W -three double bonds and two rings. -four double bonds and one ring. -two double bonds and no rings. (D) The order of reactivity (fastest to slowest) of the alcohols below in the acid- catalyzed dehydration reaction is OH SDH I CH3CH2CH2CH2CH20H CH3C‘ICH2CH3 CH3CHCH2CH2CH3 CH3 1 11 III (circle answer) III>II>I I>II>III III>I>II (E) Which of the following reactions of an alkene is a stereospecific anti- addition? (circle answer below) catalytic hydrogenation hydrohalogenation ( gromination )hydroxylation Chemistry 322aL/ 325aL ~. .7. Name Exam No. 4 (4) Contd. (F) When 2-bromo-2-methylbutane is heated with sodium ethoxide in ethanol, the expected alkeneproduct mixture is ' (EH I ’ ‘ $H (circle answer below) 3 ‘ H3 - ' ' 3 CHsCH2C=CH2 ‘CH2=CH CH3 CH3CH=CCH3 m>n>1 <m>1 I u m 11>1>m I>II (G) Which compounds below are not soluble in cold, concentrated sulfuric acid? H l ‘ (circle answer) O'CHE’ O IandII I,IIandIV . II and IV I II III . IV ‘ (H) Which of the nuclei below with nuclear spin quantum numbers of (I) will provide nmr spectra? ' 120 (I = o) ‘75 N (I = 1/2) in (I = 3/2) 12C (1 = 0) I II 111 IV (circle anSWer) IandII ' 11 and 111 1, 11 and III 1, 11,111 andIV (I) Among the four compounds below, the one with the most upfield 1H NMR resonance is (circle your answer) @ CH3C1 CH3Br CH3]? (J) In the compound below, A \ a) (C (D ClCHzCHzOCHZOCH3 the most downfield resonance in the 1H NMR spectrum will be from the hydrogens labeled (circle answer) A B G D * w?“ Chemistry 322aL/325aL : -8- Name Exam No. 4 (5) (10) Complete the synthetic scheme below by providing detailed structures of the missing compounds inside the boxes. Be careful to show stereochemical. details wherever they are important. ' Br 2 cm4 CH3CH2CH=CH2 (i) 3 equiv. NaNHz (ii) workup, _ NH4C1, H20 (i) NaNH2 _ CH as cacti W3CL+1C‘CCH1CH3 (u) CH3CH21 3 2’ ' C4H6 Forms a black precipitate C6H10 . with AgNO; in aqueous NH3. H2, Pd/C catalyst poisoned with amine H .5 E+ a ~C’ 5* L \o-u Product decolorizes Brz/CC14. . ML 0 d1 ashram/w jzém ' {W6 or Chemistry 322aL/ 325aL .i ~9— Name Exam No. 4 (6) (10) ‘ (A) ) (5) Compound A, C5H120, does not decolorize a solution of Br: in cc1‘4n Compound A reacts with a hot concentrated solution of sulfuric acid to give an hydrocarbon (B) with the molecular formula C5H10. Compound B rapidly decolorizes a solution of Br2 in CC14. Ozonolysis of compound B produces compound C which is the dialdehyde shown below. Provide structures for compounds A and B in the boxes below. ‘ 3 i fi/ 0 H hot conc. H250 L t / A, CGHIZO , B, (zen10 , " (i) 03, (21—1202, —78°C znl H20 9 S? HCCHZCHZCHZCHZCH c Chemistry 322aL/325aL . ~ -10- Name l Exam No. 4 (6) Contd. (B) (5) The "annulenesf' are a series of cyclic polyenes with alternating single and double bonds that display informative 1H nmr spectra. In the structure of the . compound [18] annulene, shown below, there are two types of hydrogens, outer and inner. At reduced tern erature,‘ the 1H nmr spectrum consists of two resonances at 5 9.3 and 5 - .0. l x ' . H0 H0 HOYK AHO H0 / Hi I H At -60°C, the 1H nmr spectrum of I '3: Hi o [18] annulene shows two resonances o \ Hi Hi | Ho at59.3 and5-3.0. A)\ He 0 [18] annulene ' 1% t 1‘ V1 Offer an explanation for the two very different chemical shifts and assign the g / observed resonances to the Ho and Hi hydrogens. Hint: Look at the annulene a a“. a "super benzene ring." Draw a picture to illustrate your explanation. C TMk «TL. chug-w x5 \‘rx T.\R-1C><Y\"KV~K11~9\ :10 \m-‘rb (ct—«c, \« Ho ’14 mm —\—\«_ \>N~ skin‘- b~€ cmA Kx-kv—rxe.\ Njaw-Hs ¥u\A)Eol jthveA—TMD a mm: Cows—KT Tk‘k rk—vx3 CU or: -V\+ MCI-X GK Q$Soqxoj~<5L \floncLCL ML 'KLh‘q -¢—rL\d)\AJ -\~\~a_-\— Ecru—w“) or (I? ' «Rm—cs Bo, T‘ka \‘K‘vxkf‘ H CPR) 'SVY‘ "K "‘ 3"“‘1\A?q\i SLK‘VDY‘ (Bo “‘k\ Qk‘Az ‘\"I\( Ou‘i‘r V H 5T1" \fk Ox 4‘— "“> \\\\‘¢- \Atme 5:. g RP, / b 4“ / //——\ HT Q??20~Y‘ o.-\- ...
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322af02_e4_key - KEY ~ CHEMISTRY 322aL M Please ’ EXAM...

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