215 Exam-00-3 - .27" Chemistry 2 1 5 Third Examination...

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Unformatted text preview: .27," Chemistry 2 1 5 Third Examination March 28, 2000 . . Name Dr. Edw1n Vedejs (Sec 100) Please Print Dr. Masato Koreeda (Sec 300) (1.5 hr; 140 pomts) Signature Student ID # Please CHECK OFF your 216 Lab section. _101 Lecture ONLY _311 M 1-5 PM A624 CHEM SCHACH, ANDREW _110 M 1-5 PM A606 LARSEN. AMY _312 M 1-5 PM A642 CHEM CA0, GANFENG _111 M 1-5 PM A612 CHEM CLARKE. NAGASH _330 T 1-5 PM A636 CHEM STAY, PATRICK _130 T 1-5 PM A606 CHEM CHEN. BIN _331 T 1-5 PM A642 CHEM SCHEIDEMAN, MATTHEW _131 T 1-5 PM A612 CHEM CLAY, JULIA _332 T 1-5 PM A730 CHEM POON, STEVE _132 T 1-5 PM A618 CHEM SMALL, AARON _333 T 1.5 PM A736 CHEM TAN, LI _133 T 1-5 PM A624 CHEM ZHANG. BO _334 T 1-5 PM A742 CHEM ZHENG, NAN _134 T 1-5 PM A630 CHEM DENSMORE. CRYSTAL _350 w 12.4 PM A636 CHEM SCHACH, ANDREW _150 W 12-4 PM A606 CHEM LARSEN. AMY _351 w 12-4 PM A642 CHEM CAO, GANFENG _151 w 124 PM A612 CHEM TURPOFF, ANTHONY _352 w 1.5 PM A524 CHEM KOMAZIN, GLORIA _152 W 12— 4 PM A618 CHEM ZHANG. LIMING _353 w 1-5 PM A630 CHEM DENSMORE, CRYSTAL _170 TH 1-5 PM A606 CHEM CHEN. BIN _354 w 1-5 PM A742 CHEM HANN, CLAYTON _171 TH 1-5 PM A612 CHEM CLAY. JULIA _370 TH 15 PM A636 CHEM STOY, PATRICK _172 TH 1-5 PM A618 CHEM TURPOFF. ANTHONY _371 TH 1-5 PM A642 CHEM SCHEIDEMAN, MATTHEW _174 TH 15 PM A624 CHEM HANN, CLAYTON _372 TH 1.5 pM A730 CHEM poow, STEVE _190 F 1-5 PM A606 CHEM ZHANG, BO _373 TH 1.5 pM A736 CHEM TAN, LI _191 F 1-5 PM A612 CHEM CLARKE, NAGASH _374 TH 1.5 pM A742 CHEM ZHENG, NAN _301 Lecture ONLY _390 F 1-5 PM A618 CHEM ZHANG, LIMING _310 M 1-5 PM A618 CHEM SMALL. AARON _391 F 1-5 PM A624 CHEM KOMAZIN, GLORIA The exam has 12 pages in addition to this cover page. The last 4 pages include tables Of pKa values for representative acids, electronegativity values for some elements, and bond dissociation energies for representative bonds, and a list of reagents. each answer space. PERIODIC CHART OF THE ELEMENTS 10 Ne 10.81 12.011 140067158984 In 20.179 13 14 P15 S16 17 18 .AI 81 Cl Ar «Q1 28.085530.9PS76 32.06 35453 39.94: K18 20 24 25 25 27 29 31 32 33 34 35 Ca Cr Mn Co Niza Cu Ge As Se Br 38.0983 40.06 47880 50.9415 51396548380 55.847 588332 58.68 63.546 65.38 6872 7259 4.8216 78.96 78.804 8380 37 38 3Y9 45 46 47 48 49 50 51 52 I53 Rb Sr Ru“ Rh Pd Ag Sn Sb Te Xe“ 85.4678 87.62 88.8058 9122 (98) 101.07 (2.. I 106.42 078m 112.41 114.82 118.892 121. 75 127.50 268M5131296 56 [£57 58-71 7292 :73 75 76 78 78 80 81 83 Ba um. Hf Re Os Ir77 P1 Au Hg TI Bi Po 9064127938391? N'DES 179.49 191947919395 186.207 190.2 192.22 19508 195966 20059 204393 207b.2 2mm (209) (:0) (222) gfififiifli ACTIN— IDES (E62) (283) 58 59 61 82 64 86 67 68 69 70 71 m s .. Ho ., .. .. .. 140.12 1403- (145) 150361559 152.50 61.10 167.26 68m42173.04 174.967 91 83 97 88 100 M801 N502 L103 lam 2&021 1K (243) (247) (247) (251) (252) :57) (253) P2590) (ZLSO) (:23) Individual point values are given in the comer of GSI Initial Name page 1 l (22 points) 1. Given that structure 1 is aromatic, is 2 aromatic? Explain using 1—2 sentences. H H H H M A H N H H No H h H/ \H 1 2 2. Given that structure 3 is not aromatic, is 4 aromatic? Explain using 1-2 sentences. @0- 3. Why is structure 5 aromatic? Draw the key resonance structure and explain briefly. U! I 4. BACKGROUND: Structure 6 has two proton NMR signals in a 2:1 ratio. This evidence was used to deduce that 6 is a hybrid of two resonance forms as shown. The chemical shifts indicate that 6 is aromatic (Myers et al., J. Am. Chem. Soc., 1992, 114, 10986). Therefore, the sp hybridized carbons of the alkyne or the cumulene (C=C=C=C unit) can be part of an aromatic ring. QUESTION: How many 11? electrons take part in aromatic delocalization with 6 using the 4n+2 rule? H HVYHH HWH l l ICII lCl II III Hint: each sp carbon (marked with C's) has two mutually perpendicular p-orbitals. Name page 2 ll (16 points) 1. Suggest a way to prepare structure 7 from benzene. Be sure to show the sequence of steps and to specify the reagents that are needed. CH Cl 3 2. Suggest a way to prepare structure 8 from 9. Be sure to show the sequence of steps and to specify the reagents that are needed. OCH3 8 CH2NH2 OCH3 9 NHZ Name page 3 III. (16 points) The text mentions (p. 790) that 2-fluoromethoxybenzene gives 10 and 11 upon electrophilic nitration. In a related nitration Smith et al. (J. Org. Chem. 1998, 63, 8448) report that 12 gives 13( (major) a)nd 14 (minor). major minor OCH3 OCH3 OCH3 Cl Cl C o 61(er <er or (T (T —> + OZN 1o NC)2 12 13 14 N02 Draw a closed shell (octet) resonance form of the cationic intermediate in electrophilic addition from 9 leading to 10: from 12 leading to 13: Which atom, O or F ,is the dominant directing group in 9? Ans. Which atom, Cl or F , is the dominant directing group in 12? Ans. Is the result consistent with the inductive effect (electronegativity) of Cl vs. F ? Ans. Is the result consistent with the inductive effect (electronegativity) of 0 vs. F ? Ans. IV. (10 points) Show the intermediate and two products formed in the reaction below. The products do not contain phosphorus. Their NMR spectra show identical ratios of protons at sp2 and spa carbons , but the products are not mirror images. intermediate: CHO H H H P< /CGH5 C4 H9 Li OXNCOZC(CH3)36 @l \C H —9> H3C CH3 9 c H6 5 Br 6 5 products: (J. Med. Chem. 1999, 42, 2716) Name page 4 V. (12 points) Draw the starting material and final product in the following synthesis: lde et al. (Bull. Chem. Soc. Jpn. 1999, 72, 2501) n“H 1. C H L' 4 9 ' CHZOC(CSH5)3 2 O H I: U H l HgCI H 0 CH oc c H 2' 2 H30 2 ( 6 5)3 CHSOH 3. pH? VI. (14 points) Suggest reagents for each of the following steps, and show the nucleophile and the enolate intermediates; be sure to include ALL reagents needed for conversion to the indicated structures as the major products. Villieras et al. (Syn/ett. 1999, 1057) An enolate H3? A nucleophile tertC4 Hg‘Sli‘CHgg O o _> + CH3 / CH2=CHBr page 5 Name VII (20 points) (J. Org. Chem. 1999, 64, 8263). fi/ocn3 i \ H OCH3 CGH 13 (1 equiv) + ANA / 15 A (1 equiv) . . 17 (phosphorous-containing “CI (1 equiv) 16 product before acidic workup) NH3-saturated ethanol concentrated NH4OH 100 DC "‘1 CeH 13 18 H a mixture of racemic / diastereomers 1. Draw in the boxes provided the structures of phosphorous-free product 16 and phosphorous- containing product 17. If a racemic mixture forms, show the stereochemistry of one enantiomer and write "and enantiomer“ in the box. 2. Provide in the box below a mechanism that accounts for the formation of 16 and 17 from 15. page 6 Name VII (continued) 3. Provide in the box below a mechanism that accounts for the formation of 18 from 16. VIII (10 points) (J. Med. Chem. 2000, 43, 22). Draw in the boxes provided the structures of the synthetic intermediate 19 and the product 20 expected from the reaction below. If a racemic mixture forms, show the stereochemistry of one enantiomer and write "and enantiomer“ in the box. OCH3 H N-bromosucoinimide \N/CHZCFS (NBS) (1 equiv) )\ —> benzoyl peroxide 0 (P (catalytic amounts) Br CH3 hV, CH2C|2 (1 C(Crah equrv NaH (1 equiv) 19 20 page 7 Name IX (10 points) 9'3 9'3 H30 \ Harl‘JBr/l/ H30—?—N:N_?_CH3 CN CN 21 (catalytic amounts) BU3SnH (1 equiv) benzene, A 22 (C13H19N028) no aikenic H's according to the H1 -NMR spectrum 1. Draw in the box above the structure of the major product expected from this reaction. If a racemic mixture forms, show the stereochemistry of one enantiomer and write "and enantiomer“ in the box. 2. Explain the role of azobis(isobutyronitri|e) (AIBN) (21) in this reaction by providing, in the box below, a mechanism by which AIBN decomposes upon heating. We as Hac—c—Nzw—c—CHg, ON ON 21 page 8 Name X (10 points) (J. Org. Chem. 2000, 65, 96). NaN02 (1 equiv) CH3COOH H20, 0 - 5 °C ———_———> H’ N4 1. Provide in the box above the structure of the major product expected from this reaction. When a racemic mixture forms, show the stereochemistry of one enantiomer and write "and enantiomer“ in the box. 2. Draw in the box below the two significant resonance structures of the electrophilic reagent generated from NaNO2 and CH3COOH in H20. Page 9 E S m 9 H E \o .m\ e. e e: e H A OHC .. ®\ I "S” \NlH e ”O” ..C\ G / .. .OHN H _ OHC _ . \ / e U ..o- n c/ 2 / O 2 OHC H e o. J G. .o H 3 _ H / 1 1 c e e H e H ) N e: a. H H c, m c1c1c 5 9 H1 cx H .. \ n O m C H C _ C H N __ x C/ G a C G _ / C C1.IC\ H e B C H H \ / I I H HICIH s H C _ w... H m 2 r a 2 r. K w 0 M O .01 p 1 1 5 7 1 H n 9 o H H 2 3 % [am 1 . . 4 3 m l .\0. H H cu\ H/ H 4 m.) C OIC 1C / NIH H .. x H H H A / .. @x x 2 I \ . \ .o x H _ .0. OH H H 011C .0 ./ C _ H H . . N C / .. \ / GI 11 C H z \ H 1/ G v "m. 3 / H2 OHC H CIC 5 H2 .. \ C H H/ \ 1m .0 c H H c / _ c HIN __ / c/ H H c G . C "m. "m. G _ / C CHC\ H _ A C C H H Hx /H HIJCIH m E / \ H 1m S e A 1o M E B .0.. e T r. .. . - . e e H A s 01 .. .. .\ H .. G G ban. .. 14.3.. "I” o. no \ ®uou ..o.. e a .0. a. . / 0 Oil \ o\ o e H/. c\H U W. .H. um. / IN/ OHC O N G 3 .J C H . / F. OHC\ H _ 9 H G N In. um: 0 C3 /C\C .\O. O \C O C e G. OHC I \ OHC e O C oIC /. N H _ / / C. __ x C 3 / x / _ H C\ a 9 /3 e _ / K _ 9 7 4 7 "Fm H D. _ _ 7.. .L 3 4 _ .I_. % 2 2 W 3 4 ,% 8 m .m. 4 w 2 D m “OHrHO \H H H .H H 9 9. Wm 0. I We . _ . ._1 . 0" Hlmv/ HI®O\ @ \O .\O” O” H 3 m C 0 .m. H _ 2 ../ OHN OHC F OHCx H® _ H H A U H H H / / INIH ”O. H \C Kw C; O C; % Hz \r_C .mu \ . \0 OHC/ H H m e c c\ _ ..1C/ onc/ \c,\ N 3 H m 3 .0” =_ I. / H 0 . C/ H C H wIH /C\C C H "m. _ H _ c H / page 10 Table 1.2 Electronegativity Values for Some Elements 1 2 13 14 15 16 17 Table 2.4 Average Bond Energies [kJ/mol (above) and kcaI/mol (below)! Single Bonds flflflflflnfln Si 364 499 393 35] 103 87 271 347 305 360 485 339 285 2] 8 page 11 The Reagent List Shown below is a list of key reagents (not always the whole recipe) which may be useful for solving questions on the exam #3. Reagent classification or specialized use Chapter 13 NaBH4 nucleophilic hydride reduction LiAlH4 nucleophilic hydride reduction RMgX nucleophilic carbon RLi nucleophilic carbon Raney Ni desulfurization HSCHZCHZSH thiacetal/thioketal formation 4-CH3C6H803H (TsOH) organic-soluble acid C5H5NH+ ClCrO3' oxidant ClC(O)C(O)Cl/H3CS(O)CH3 then (CH3CH2)3N oxidant HZNNH2 hydrazone formation HZNOH oxime formation BF3-O(CH2CH3)2 Lewis acid source (CH3)3C(CH3)ZSiCl (TBDMS-Cl) protection “3? 9H3 H30-9-$i-Cl H3C CH3 (CH3CH2CH2CH2)4N+F nucleophilic F' source dihydropyran (CSHSO) protection 0 0 Chapter 14 AgZO, NaOH, H20 oxidant Chapter 15 (C4Hg)2AlH (DIBAL) Lewis-acidic reduction hydride source Chapter 17 KH base LiN[CH(CH3)2]2 strong base Chapter 19 RZCuLi and RzMgLi conjugate addition nucleophilic substitution P(C6H5)3 phosphorous nucleophile RR'C' - P‘(C6H5)3 Wittig reagent RC(O)CHR'P(O)(OC2H5)2 modified Wittig 1,3—dithiane KW svs HgClle-IZO (Homer-Emmons) reagent a carbonyl equivalent thioacetal/thioketal hydrolysis page 12 Chapter 20 Chapter 21 Chapter 22 Historical From Chem 210 X2/FeX3 (X = Br, Cl) HZSOJHNO3 or NaNO3 RC(O)X/A1Cl3 (X = Br, c1) sto4/sos N—bromosuccinimide (NBS) benzoyl peroxide azobis(isobutyronitri1e) [AIBN] 9'3 9+3 Hac—cls—NzN—e—CHS ON ON (CH3CH2CH2CH2)38m SnCIZ/HCI NaNOZ/H3OVHZO, 0 °C CuX (X = Br, Cl, CN) H3PO2 (hypophosphorous acid) HZNNHC(O)NH2 HZNNHC6H3(NOZ)2 OsO4 KMnO4 peroxyacid (e.g., 3-chloroperoxybenzoic acid) 03 then (CH3)ZS or Zn NaNH2 NaH K+ ‘OC(CH3)3 HZ/Pd Hz/Pd/CaCO3 BH3 or 9-BBN then HZOZ/NaOH PBr3 SOC]2 4-CH3C61-LSOZC1 (TsCl) CH3SOZC1 (MsCl) source of X+ source of N02+ source of acylium ion sulfonation radical bromination radical initiator radical initiator source of (CH3CH2CH2CH2)3Sn- and H0 reductant nitrosation of amines Sandmeyer reaction reductant For 216 labs; not for 215 exams For 216 labs; not for 215 exams oxidation oxidation oxirane formation ozonolysis base base bulky base hydrogenation hydrogenation hydroboration e.g., R-OH -> R-Br e.g., R—OH —> R—Cl tosylate formation mesylate formation ...
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