final exam 1 - 0" Li ‘.a.7 Own 33 0 Z S Find...

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Unformatted text preview: 0"): Li ‘\_.\.a\'\ ,.7 Own?) 33\ 0 Z S _, Find @ CHEMISTRY 3331 Name FINAL EXAM (print) Last First Dr. C. Cai Dr. R. Thummel S. S. Number May 1, 2002 Please read all directions carefully. Write all answers legibly in the appropriate spaces and THINK about what you are doing. Give only ONE answer for each question (200 pts total). 1. (24 pts) Give a complete and acceptable name for each of the following compounds. Be sure to indicate stereochemistry were this is pertinent as well as the absolute configuration of any chiral centers. a (f 2. (39 pts.) For each of the following reactions or series of reactions, draw the structure of the principle organic product or the starting material in the empty box ,or the appropriate reagent(s) over the empty arrow. Give only one structure per box. Be sure to indicate STEREOCHEMISTRY where pertinent. H2 Pd/C OH (b) QJ PCC D CH2012 (C) H20 0 H9304 H2804 (a) D (d) Mmflg (e) 9 CH CO H H 0+ - O UCHZOH PBr3 Mg 1- A f —-——> O 2. H30+ (d) Q 1) (WE—H CH2— C E C-H ————-———> 2) H202, H2O o3 CH3-S-CH3 (h) 01> OH (i) M’ M» 0 0L OH 30012 CH30 Na ) CH30H 1. Li \/\Br (k) >—C| ____. 2. CuBr CH3 CH3 OH O , H30+ .,H (I) ————> u 2 CH M Br H30+ (m) @C-OCH3 3 g 3. (9 pts) When methylenecyclohexane is treated with bromine in the presence of heat or light a very small amount of l,2-di(1'—cyclohexenyl)ethane is formed. Give a detailed step-by—step mechanism to explain the formation of this product. Show all intermediates, charges, unpaired electrons, and indicate the flow of electrons by using arrows (26) or fish-hooks (le'). Bra DIG A or light Minor Product 4. (18 pts) Devise an efficient synthesis for any TWO ONLY of the conversions depicted below. You may also use any organic alcohol of 3 carbons or less. Show all necessary reagents and indicate the structures of all intermediates. Do NOT give mechanisms. 0 HO / H H WW —»+a-w 0%?“ 0r“ (1“ CH3 5. (13 pts) (a) For the following structure, looking along the C2—C1 as indicated by the arrow, draw a Newman projection for the three staggered conformations. Put a star under the most stable one. (b) Draw the structure for the product of an E2 reaction of the above compound with KOH. 6. (12 pts) Upon treatment with strong acid, 1,2-dimethyl-1,2—cyclohexanediol undergoes a pinacol rearrangement to provide the two cyclic ketones shown below. Give a careful step-by-step mechanism to explain the formation of both products. Used curved arrows to show the movement of electrons and indicate all charges and all intermediates. CH3 0 CtOH H+ O H3C CH3 OH CH3 + CH3 CH3 7. (12 pts) Draw all the other important resonance forms of the following reactive intermediates. Circle the major contributor. O H G H l O HW H 8. (8 pts) How many proton N MR signals (non-equivalent protons) would each of the following molecules show? 9. (8 pts) Oxidation of a molecule having the formula C5H100 with sodium dichromate in sulfuric acid gives a substance which shows a strong carbonyl stretching band at 1780 cm‘1 characteristic of a cyclobutanone. Four possible isomeric molecules with the formula C5H100 are consistent with this data. Draw their structures in the boxes below. Na2Cr207 sto4 CsH1oO vC=O = 1780 cm‘1 or or C5H1OO C5H1oo or CsH1oO CSHmO 10. (12 pts) (a) Draw the two chair conformations of cis—l-isopropyl—3—iodocyclohexane into the appropriate boxes below. A. Most stable chair B. Less stable chair (b) In the appropriate boxes below, draw the two chair conformations of the product of a 8N2 reaction of cis-l-isopropyl-3—iodocyclohexane with NaSH. A. Most stable chair B. Less stable chair 11. (26 pts) The bromination of 2—methylpr0pane with Brz can result in two products Via reactions (1) and (2). The relevant bond-dissociation energies are: Br—Br (46 kcal/mol); H—Br (88 kcal/mol); (CH3)3C—H (91 kcal/mol); (CH3)3C—Br (65 kcal/mol); (CH3)2CHCH2—H (96 kcal/mol); (CH3)2CHCH2—Br (67 kcal/mol). H3O BI’ >—/ + HBr (1) H30 H3O >7CH3 + Bl’g H3O H3C Br >< + HBI’ (2) H3O CH3 (a) Calculate the enthalpy (AHO) for both reactions (show your work). Are the reactions endothermic or exothermic? AH0 for reaction (1): Endothermic or exothermic (circle one)? AHO for reaction (2): Endothermic or exothermic (circle one)? (b) Both reactions involve two propagation steps. Write down the two propagation steps for both reactions. (c) Calculate the (AHO) for the first propagation step of both reactions. (AHO) for the first propagation step of reaction (1): (AHO) for the first propagation step of reaction (2): (d) If the activation energies of the first propagation step for both reactions are 4 kcal/mol higher than the products of this step, draw a curve to represent the energy change of this step for both reactions. Indicate the transition state and the energy changes. Energy Reaction Progress (6) If the first propagation step is the rate—determining step for both reactions, which reaction (1 or 2) runs faster? 12. (10 pts) Two molecules differ by only one carbon atom, having the formulas C3H60 and C4H6O. They both show very similar NMR spectra: a two proton quintet at higher field and a four proton triplet at lower field. The C3 compound shows s strong IR band at 1080 cm'1 and the C4 compound shows one at 1780 cm'l. Draw their structures in the appropriate boxes below. C3H6O C4H6O 13. (9 pts) A compound with the empirical formula C5H7O shows a molecular ion in its mass spectrum at m/e = 166 and a major fragment at m/e = 121. The molecule shows a strong 1R band at 1100 cm‘1 and gives the proton NMR spectrum shown below. Draw its structure in the box. Be sure to show your work for any partial credit. 14. (8 pts EXTRA CREDIT!!) One afternoon while Professor Homer Farquardle was taking his customary nap, his deranged daughter Penelope wandered into his laboratory. She soon discovered a flask containing ethyl alcohol and so eagerly did she consume its contents that she spilled most of the alcohol all over herself. Somewhat contented, Penelope decided to really mellow out and light up a little weed. Striking a match, she ignited her number along with her person and the entire laboratory was blown to smithereens. Tearfully picking through the ruins, Prof. Farquardle discovered a tank labelled 2—butyne which no longer contained any gas but rather held a crystalline solid with a melting point of 163°C. He deduced that this substance was a cyclic trimer of 2—butyne and that it showed only a single peak at 2.5 ppm in its NMR. What is the structure of this substance? Penelope's legacy HA VE A WONDERFUL SUMMER !.’ TYPICAL VALUES OF PROTON NMR CHEMICAL SHIFTS \ Type of proton Approximate 6 N. (—CH;) 0.9 alkane (—CH,—) 1.3 (—CH—) 1.4 fl —c—CH3 21 “CEC—H 2.5 R—CHz—X (X = halogen, —O—-) 3—4 I l l l -C=C—-CH, 1.7 Ph—l—I 7.2 Ph—CH, 2-3 R‘CHO 9—10 R—COOH 10-12 R‘-OH variable. about 2—5 Ar—OH variable, about 447 lb—NH2 variable. about 1.5—4 mm These values are approximate, because all chemical shifts are affected by neighboring substituents. The numbers given here as- sume that alkyl groups are the only other substituents present. A more complete table of chemical shifts appears in Appendix I. Frequency (cm‘ 1) F unctional Group Comments 3300 alcohol . 0—H always broad _ amine, amide N —-H may be broad, sharp, or broad with spikes alkyne EC -H always sharp l 3000 alkane ~(IZ—-H just below 3000 cm ‘" ‘ alkene =(l',‘—-H just above 3000 cm“' acid @—H very broad 2200 alkyne ~CEC— just below 2200 cm"1 nitrile ~CE just above 2200 cm“ 1710 carbonyl >C = O ketones, aldehydes, acids (very strong) esters higher, about 1735 cm" ‘ conjugation lowers frequency amides lower, about 1650 cm‘I 1660 alkene >C =C< conjugation lowers frequency 1 aromatic C=C about 1600 cm“1 ‘ . . \ / mune /C=N stronger than C=C . \ amide / C=C stronger than C = C (see above) Ethers, esters. and alcohols also show C—O stretching between 1000 and 1200 cm". ’ E 2A 3A 4A 5A 6A E 7A ; ‘ '1" "E “if???" "fin—9"” . 191 . .2 N E o E F i 9.012 2 10.81 E 12.01 ‘ 14.01 E 16 E19.00 I vl’_.'¢7_v-1’y.im E 1 E531...- !%4_2§!‘3-E_FJEEM ; 1‘1"" 2.5 31 . if E " ' '4‘ 3 M2 22881ME 2.2 E .. 1’": .33 ~.-....§E-....__.7B. TIET W .113, . 291m Imuyflnam mm ‘2 D E' 20 E 2 23 E 24 E 25 1 26 E 27 ‘= 28 I 29 E 30 i 31 = 32 33 2 34 35 042 c6. 2 EV1CiEMnEFe CoENiECuEzii Ga Ge AsESe Bi E 39.10 i 4008 ‘E 44.96 1 47.86 2 5.94 E 5200 | 5494 E 5585 5893 E 5870 6354 E 6539 69.72 72.61 74.92 7896 7990 in Miami 918101.. VSundlung Eng-019mg Egg. gg; MELIg-gqnm ”'2’: , 0131113“; Nickengmggpw Zinc TL_I§g_ugmg__,*<9_n_vg-‘ngug Anni: £11811 Bromine E“ 1' ‘37 E 38 "39 5 40 E 41 E i 44 T 776 ’ 47 ““‘E’ 43 I 49 E 50 E 5E802512Y221.N12:M91Tcinn RnEpaEArca InESnESb 85.47 E 87.62 . 88.91 ‘ 9122 E 9290 ~‘ 95.94 ~ (98)10107 1029 106.4 107.9 E 112.4 _ 114.8 I 118.7 121.8 127.6 126.9 Rubidium ismu‘um E YL!!1ug__LZJ_I§gq§gIggg_E Niobhm EMonhdumeTechnefium nglfg; E 131205L __ Psi-dim $511175: gdgifi‘. Indniin Tm EAngigggL leurium _51:11q1n__efl_ E“"s“5"""'”E”§6 "E ‘57 E 72 E 73 'E 74 2 75 76 E 77 . 7s 79 80 81 E 82 83 84 6 Cs ; Ba ; 41.1. E at ; Ta ; W E Re Os E I: E Au H 2 11 . Pb 31 Pa 132.9 imzz 2 138.9 178.5 E 18094 . 183.84 186.2 190.5 2 1.92.2 1951 E 197.0 200.6 1 204.4 = 2022 l 209.0 (209) 95in: 5, Barium EpnlhlniquE 1:151?ng I Tlign_1gig__1_1mgmn 510551).an 0gmgm~E w1514119“E~_1_’l._lti.11ggi~ii. L” 9918*” Meiwry Mum E .. ' . 8‘7"?“ §§“'E 89 a" 104 I 105 E 106 E 107 108 109 2 110 E 111 112 - > ~ - 7 Fr E Ra E EAC E Rf E 262 E 255 E (262) E (11:58) E (g E (7469) E (272) (277) 444%..22‘14fi31 “2474’ 24‘23344 ‘D E ‘ _’_..'144E:44_.L4-444 1444-4441 21.2.-.2... ...
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