322af03_final_key

322af03_final_key - CHEMISTRY 322aL/325aL Please K FINAL...

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Unformatted text preview: CHEMISTRY 322aL/325aL Please K FINAL EXAM Print Last ame DECEMBER 11, 2003 First Name SSN TA's Name Grader (1)(45) _____ (2)(20) Lab Day 8: Time (3)(20) (4)(15) _____ ______ (5)(30) (6)(15) (7)(15) ._____ _______ (8)(10).______ (9)(10) (10)(20)_____ (200) first letter of last name I will observe all the rules of Academic Integrity while taking this exam. Chemisz 322aL/325aL -2- N e____ Final Exam 7 f £4 CZ , (1) (45) 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. Show or describe stereochemical details in the products wherever they are important, including a racernic form of a chiral product. "Workup" means adding water and bringing the solution to neutral pH. (A) CH3CHBrCI—{3 + NaOCI-IZCH3 ethanol cuscnqul (i: AM 0 E1— decolorizes Brz/CCI, TL % ' Z 0 in ~ M ) : , C3 product gives ppt with I AgNO3 in ethanol H3 (C) CH3CH2W C}: excess H2 ’ CHZCECH Pt 100% ee H COI'IC. H2504 (D) CH3 heat H\ 9H3 (i) 0504/pyridine (E) c: CH3CI-I2/ RH (ii) NaHSO3/HZO Chemistry 322aL/325aL -3- Name Final Exam (1) Contd. H3 (F) CH3§HCH=CH2 + HBr —-—T———> CH perox1des 33:14 «Hzng, Man; «(I-(g Jr (i) hot KMnO4, HO‘, H20 (ii) workup (G) C6H1004 product shows three resonances in 13C NMR CGHSC :- +Na + CH3CH2Br NH3, _330C ZIICIZ (I) CH3CH2CH2CHZOH + HCl heat j/A Etf‘Cl/‘Cl/z I C ' product does not decolorize Brz/CC14, ,7, mm“, gives a ppt with AgNO3 in ethanol CH3CH1C £429qu Br H k (J) + PBX‘3 —_"'—> CH 5 racemic form product gives a ppt with AgNO3 in ethanol 0% an? a/KML Chemistry 322aL /325aL -4- Name Final Exam (1) Contd. 8H3.TI-IF ———-———-> (K) tetrahydrofuran CH3CH2 (i) Hg(OAC) THRHZO (L) M 2 (ii) NaBH4, NaOI-I /C 5 CH . Et3N: Hun-C + (M) \ CH3 CH2CH20H 100% ee $H3 (i) NaH (N) C6H5CHCHZOH (ii) CH31 racemic form 03H (0) + Mg2+ ———> C“‘3 COZ_ ethanol CH3 CH3 2 C7H120 achiral product Chemistry 322aL/3253L -5- - Name Final Exam (2) (20) Answer the questions below. (A) (10) All valence-level electrons are shown in the structures below, but charges are missing in some cases. Place any missing formal charge directlyiext t the atom on whichitresides. (A r . g 3W: (B) (10) Indicate on the line below each structure whether the structure is chiral or achiral. Identify all stereocenters in each structure with an asterisk (*). A stereocenter is defined acco ing a the de ' 'tion in lecture a in our ext. w W tow (A i6 1407‘ 7[0 *- CH CH3 (CH3)2CHCH2C1 CH3CI-I2CHC1COOH * H H Catch} [ex C\~\r-a.\ (EH3 I r EH r- th ra.\ (\ngraA (UL: ck! Chemistry 322aL/325aL -6- Name Final Exam (3) (20) Answer the questions below. (A) (6) Draw detailed structures of the following compounds in the boxes below. Your structures must show any stereochemical features indicated in the name. (E)-5-cl"lloro-2-penten-1-01 1,3,3-trimethylcyclohexene (B) (10) Indicate whether each of the following pairs of structures represent the same compound or whether they are enantiomers, diastereomers or constitutional isomers. CH3 CH3 OH HO H H Chmva-‘d‘ b ‘2 ¢ VS S? T013 I‘I_|'—_C6H5 Cl _».. —.. ---. . _ .._~‘---—M~.fl.a. Chemistry 322aL /3253L -7- Name Final Exam (4) (15) The 1H NMR spectra of three constitutional isomers of (251-1100 are shown below. In the box below are possible structures. Draw a structure consistent with a spectrum in the box to the left of the spectrum. Circle groups of magneticaliy equivalent H in each structure, and draw an arrow from each group to the corresponding resonance in the spectrum. ‘ ' R . l l CH3CH2CH2CH2CH CH3CH2CCH2CH3 043%ch3 CH3CH2CH2 CH3 CH3 . U ' Q C HSQHL CHICHS lat " Chemistry 322aL/325aL -8- Name Final Exam (5) (30) Circle the correct answer for each statement or question below. (A) The molecular formula for the structure below is (circle answer below) C7H1231’ / N C7H14BI' C7H1581' Br (B) According to VSEPR theory, the bolded central atoms in the chemical species below that have trigonal planar geometries are (circle answer below) 112C‘———CH2 CH3-C__—_ C-CH3 NH3 H3C+ H30+ 1,11de 1,111, andIV 1v v I H m IVandV (C) The order of acid strength (strongest to weakest) of the following compounds is (circle answer below) CH3CEc-H NH3 H20 CH4 Cfi>1>11>1v D III>II>I>IV I H III IV II>III>I>IV I>III>II>IV (D) The constitutional isomer of C5H100 below with the highest boiling point is 9 (circle answer below) CH3CH2CCH2CH3 . Q (E) The Newman projection formula below is a staggered conformation of H3 H H (circle answer below) \ .3 isobutane 2-methylbutane 2-methylpentane 3-methylpentane H Chemistry 322aL/325aL Final Exam Name (5) Contd. (F) The lowest energy conformation of methylcyclohexane is (circle answer below) ((3) The rate expression for the reaction R-X + Nuz' ——-—> R-Nu + X:' is rate = klRX] [Nuz']. The rate of this reaction will be fastest in which of the following solvents? CH3OH' H20 CH3CH20H (circle answer) (H) The major product in the acid-catalyzed dehydration of trans-Z-methylcyclohexanol is expected to be (circle answer below) H ....\\\CH3 H+ ¢CH2 H3 H3 H3 -—> ('H20) (1) The proton-decoupled 13C NMR spectrum of a compound C6H14 shows 5 resonances. This compound is (circle answer below) CH3CH2CH2CH2CH2CH3 m qHs CH3CHcHCH3 CH cHs 9H3 3 CHsgISHZCHs CH3CH2CHCH2CH3 3 (J) The monochlorination of 2,3-dimethylbutane at 300°C gives a product mixture of 60% l-chloro-2,3-dimethylbutane and 40% 2-chloro-2,3-dimethylbutane. 9H3$H3 C12 9H3$H3 9H3$H3 CH3CH-CHCH3 ——> CH3CH-CHCH2C1 + CH3CH-¢-CH3 3000C 600/ 40% C1 The relative reactivity of each type of H (on a per H basis) under these conditions is (circle answer below) reactivity of a primary H 3 /2 2/3 = 4 / 1 reactivity of a tertiary H 1/4 ,._...v—....._—’- Chemistry 322aL / 325aL -10- Name Final Exam (5) Contd. (K) Photochlorination of a racemic form of 2-chloropentane produces a number of dichloropentane products. Among them are 2,3-dichloropentanes. How many different stereoisomeric forms of 2,3-chloropentane are produced? (Hint: Not all the forms are separable by physical methods.) 2 3 ® 8 (circle answer) (L) The weakest C-H bond in 2-methylbiitane in a homolytic bond dissociation is B CH3 b C Ax f (circle answer below CH3-¢-CH2-CH3 A‘ B H\D (M) The reaction of 1,2-dimethylcyclopentene in the sequence hydroboration and oxidation involves the stereospecific processes, respectively, of (circle answer below) CH anti-addition and inversion anti-addition and retention syn-addition and inversion CH3 syn-addition and retention (N) In the initial step of the oxymercuration reaction of an alkene, the mercury (II) acetate acts as a(n) 8H3.THF H202, KOH -———__>——-——> (circle answer below) H O - /\C=C< + Hg(OAC)2 —2————> ‘ - nucleophile tetrahydrofuran Lewis base radical initiator (0) Which synthetic methods below will convert an unsymmetrical alkene to an alcohol with overall Markovnikov addition regiochemistry? synthetic methods I direct acid-catalyzed hydration II oxymercuration—demercuration III hydroboration-oxidation ................. u, Markovnikov addition onlyI Ianle RCH=CH2 I, II, and III (circle answer) Chemistry 322aL/325aL -11- ' Name Final Exam (6) (15) Answer the following questions (A) (5) The allyl carbocation is unusually stable for a primary-type carbocation. Resonance theory explains this special stability. In the boxes below, draw the contributing resonance structures and the hybrid of the allyl carbocation, Your structure of the hybrid must show correct charges and structural symmetry features. ("A . , I 9-.— + CH2=CH- CH2 allyl carbocation resonance structures hybrid (B) (10) When isotopically labeled allyl bromide reacts with ethanol in an 8N1 ethanolysis reaction, the label is scrambled in the product as shown below. 5N1 13 CH =CH— CH B 2 2 r CH3CH20H l3 CH2=CH—13CHZOEt + CH2=CH——CH20Et 50% Write a mechanism that explains this result. Identify the rate-determining step in your mechanism and use the curved arrow formalism. Circle the key intermediate and clearly show how resonance theory explains t ' . ® :3 (H z l3 A\\Y\ CkrBoLm—lfiom is KL'T \\+<Vmihk-‘\€- Tbx \w bfii Vng‘k‘S NW &‘\-\I\AN\0\ mark/C 0_fi\)a.\ PW‘Q Lb:[d“] cd~ {Lek flfmldkcv.‘ Co‘vbox ~ CHC be + _ -- - HL l, Gui—cH~CHZ<DV>t+ \ . a CH CH 6&4 ’3 6C V CHL: CH— EH2: ' “L04: So/s ”‘ _ : C CHSCHLQ CHL CH HA r-.. o/ Chemistry 322aL/325aL -12- Name Final Exam (7) (15) Answer the following questions about the synthetic sequence below. (A) (9) Provide conformationally correct lowest energy structures for A,B, and C in the reaction sequence below. Assume that the t-butyl group is larger than any other substitu'ent group on the cyclohexane. Indicate in the shadow boxes next to the arrows whether the reaction step proceeds by inversion, retention, or racemization at the stereocenter in the cyclohexane ring identified by an asterisk. OH H2" (1) NaH ,cH-s i (ii) CH3CH21 ’ H C(CHS)3 s. H CH3SOZC1, amine base Rth-fw’fi o o s 1’ 3 NaOCHZCH3 H i B C3111422303 C C12H24O (B) (6) Compounds A and C are isomers according to their molecular formulas. Are they constitutional isomers, stereoisomers, or conformational isomers? Select one fthese terms. gfifl O (s O M9 vs. Do you expect A and C to have identical physical properties or different physical properties and why? Be very specific in your answer. Tkt7/ kgvg Ar£+¢c¢ «T E>\N‘{$LC QK ?r°?‘P-H(S @ lace qv $1 QC‘K d: Q$$ *‘OM‘F5 ’— MO.T NC mesa/r m flee/5ipr WW -- --~- - ?.wqa.._;_ Chemistry 322aL/325aL ~13- Name__ Final Exam (8) (10) The acid-catalyzed dehydration of 1,2,2-trimethylcycloheptanol (I) gives the alkene product II. Write a plausible mechanism that explains this reaction. Use the curved arrow \) formalism in your mechanism and circle all key intermediates. Identify the rate- determining step (RES) in your mechanism. CH3 cH ' c933 ___->. a PLH ‘l— HZ‘OH c L “H20 \J H CH3 C65 Rmi (“dead-1 M : EFL“ Ewes tum-v. slime / k’ 3 "cask é~m4u~§¢c~gé Pram; \ \‘2. ot\\4m~;42 L! ser ‘f— GB + HéH —> \\/ + “to DQPV‘DHNAW 0 "A 21%“ ' CH5 3. %3 {ts—b 3 Chemistry 32231. / 325aL -14- Name Final Exam (9) (10) Ethanethiol (CH3CHZSH) adds to propene in the presence of peroxides (RO-OR) to give ethyl propyl sulfide. RO—OR CH3CHZSH + CH2=CHCH3 . CH3CH25CH2CH2CH3 ethanethiol ethyl propyl sulfide The mechanism of this addition is a free radical chain initiated by the following steps: RO-OR 2 RO ' . alkoxy radical initiation R0' + ‘ + CH3CH28° ethyl thin radical (A) (4) Based on the above information, write out the two propagating steps for this chain reaction below. Propagating Step 1 Q H3CH?_g . + CH1: CH c H 5 —% CchHzS— CHI-CH C H3 9w» ’6“ C Propagating Step 2 c pquzS-CHLC‘HCHS.‘\‘ CchrtzS—H —> GHQHECHS‘SE * (B) (4) Based on the following DH° values, calculate the standard enthalpy change Cl‘lgcuzs’ (AHo) for each propagating step, and the overall standard enthalpy change for the reaction. Place your answers in the boxes below. Some DH° Values in kcal/ mol RS-H RS-CHZ- TE bond in alkene R'C'H STEP l me: (- SG)”L_GO\ 1 + L—\ KCqJ/Mo) mi": (41834473 +“" R; 1 _'2t, KC9/Mol -zzkg I rm 1 step 1 step 2 overall (C) (2) Briefly explain the observed regiochemistry of this addition reaction. TL‘K Mum sfik\z C-\‘<.\/l t‘tétce‘l \s \(‘Drvwi K) - -c CH ethg. +~ CHL2QHCH3 .__> QHsQHLS QHLQH HS 2: Q Mow. fi-l-v-lo\§ A FQHz‘Hs QH'C'Q —C++ ’—> mean»): + H): H \g. -CH2—-&~QH3 “Us Chemistry 322aL/325aL -15. Name Final Exam (10) (20) The table of reagents below may be helpful in answering the following questions. You are not limited to these reagents in designing your syntheses. Common solvents and acids and bases may be included as needed. Table of Selected Reagents HBI' HI \ P Bra Brz H2 / Pt Hz/Pd(poisoned) NaBH4 NaNHz NaH NaOEt KOBu-t NaOH Hg(OAc)2 KMnO4 O3 3H3.THF H202 (peroxides) (CH3)3SiC1/ amine base MMPP (magnesium monoperoxyphthalate) You may use other reagents as well in your syntheses. l? I CH3 ---------- - - ‘> H “L’r\7\&\/Qlo'?l’v<\<otmt (s om.\\—2LL Q'V'QL Y'ki'l c...\ ‘DVOMT’V\~HO’V\ - H> 5‘91 Q Hi“ l‘h/ baa-cl" Chemistry 322aL/325aL -16- Name Final Exam (10) Contd. (B) (10) Design a reasonable synthesis of 1-propoxy-2-propanol from propene. CH3CH=CH2 """""""" ' ' '> OH 1-propoxy-2-propanol Mm P P ‘ O C S—H-u (:‘rud‘L "Raf V" 9 _ CH CH ~CHZ ¥ «9cm (HQH m CL; CHQH-OQK CH CH OH ...
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322af03_final_key - CHEMISTRY 322aL/325aL Please K FINAL...

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