345 Exam 1 - Yoon - Key

345 Exam 1 - Yoon - Key - Name: ‘ Student lD#: Exam 1 -...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Name: ‘ Student lD#: Exam 1 - Chem 345 Professor Yoon September 25, 2008 75 minutes Please read these instructions carefully before beginning: 1. Do not open exam until 9:30. You will have 75 minutes to complete the exam. 2. The final three pages of this exam are blank. You can tear these off and use them to work out your answers. 3. Final answers must be written clearly in the proper space provided. No credit will be given for illegible or ambiguous answers. 4. Model sets may be used, and tables of NMR data have been provided at the end of the exam packet. This test is otherwise closed-book and Closed-note. l verify that the work presented on this exam is solely my own. I understand that evidence of academic misconduct will result in ejection from the course and a failing grade for the semester. Sign: Problem 1. (8 points) Are each of the following structures aromatic, anti-aromatic, or neither? Hac\@/CH (1745299 , Name‘z \ / NO P orLR’ml NAMATlL Iqa— : up +1 C] l Max M IA M‘nL /N® My?)th Cl 4"- WWM‘no LN Problem 2, (12 points) How many signals do you expect to see in the 1H and 13C NMR spectra of each of the following molecules? » n r, {Amaraan awn“ “A O H H 5 , Br W H number of g 5 L‘ ’H NMR signals number of 13c NMR signals 8 S 3 Problem 3 (15 points) You havejust completed a synthesis of one of the isomers of dimethoxybenzene, but you don't know which one. Draw the three possible isomers of dimethoxybenzene and explain how you could use 13C NMR to tell them apart. I ‘ l 2 q ‘ (SCH; ' 3 om;3 ‘ 9%0 1“ OCH; I 3 OCH 3 T S :I CH3 Om Wk F>YL E‘av‘a CHM Wovdé 7‘ “4(fiue. \AV‘MM‘U“ 1"?» $'\§fi)\s ifl m \‘C/ SP 0“ NM 3 M 4K) M f” . M OHM) new wm\L Yaw/«.4 L3 S‘goflsg AN; thx \smU W‘Q ?n<§’uc~ § flaw/ks; 7»; W4. FM'L Raw vooMé '3. 7 Fflwa & 3A7\\ . Problem 4. (15 points) The structure of calicene is shown below. ©=q calicene a. (10 points) Most hydrocarbons are non-polar, but calicene has a very strong dipole moment that has been estimated to be as large as 5.6 D. This value is several times larger than the dipole moment of water (1 .8 D). Explain why calicene is so polar. (Use resonance structures to support your answer.) @543 H \/9 {39¢ H egf—Qcfl (a GM K W (D 2. You cm 3v»: 9,,ch MSOA‘MUL dnm’mzs in mm“ a“ at? M “MW Amity low M (mm C=c \WA is xx m. S—wmkné nub, BOW fi'xbx ix «West clmrvzszA regain/yak SAMCHNS m enlvw’hu \ so MK. 3+“de aw g\‘3‘.\{l«‘m¥ MAHWrs "\‘b VHAL WAX restmuua éhfium :Q m whrmkn.» 8M 0‘“ mm WC»; QKW‘F slskfifim sv’fifl \sosr’nw my?» SAM 3’ WWX rx‘flg VA vfl‘g)‘ NSth vCM‘n‘L .U‘ M S- TWMeMA r Ag , u b. (5 points) Would you expect the barrier to rotation about the central carbon—carbon double bond of calicene to be larger, smaller, or about the same as that for a normal carbon-carbon double bond (e.g., ethene)? Explain your answer. szuu-g Each a)? m» anwth "CQMW—L stucth walks)“ ’9.“— 7x 00mm (x C, «31$; bml 4 \A ‘M, prosQ—L RSbKVng \> WV“ 4 W1 W0! ml.“ 4W \ “Wu, lowl a MRI r? m LNG“ 7\ 3' «8 9mm“ EC sew/“A3 red/M9 L _ ' Problem 5 (25 points). A compound with molecular formula CQH13N has the following 1H NMR spectrum. .J_LJ_L_L.I_LL_LI_J_‘_L_LL 1.45 L40 1.35 ppm 7.29 /— 5.15 1.75 1.70 1.05 1.60 1.55 ppm J‘ 090 [L85 [1.80 M ppm W 7.30 7.25 7.2-) 7.15 ppm 3.80 35’?) 3.70 10 9 8 7 s 5 4 3 2 l 0 ppm a. (4 points) What is the Unsaturation Number (or index of Hydrogen Deficiency) for this compound? Li b. (6 points) You can deduce partial structures from several of the signals in this spectrum. What substructures account for the integration and multiplicity of the signals in the spectrum with the following chemical shifts? 6 0.85 ppm 6 3.75 ppm 6 7.26 ppm H CB3“ 0“7,+ §—%s “LL-$- H / ‘ + H :rkll pi c. (5 points) Draw the structure of the compound. NHL @/\V CH3 Problem 5 (continued): d. (5 points) The peak at 6 1.40 ppm disappears when a drop of DZO is added to the solution. Why? WM 510 {g Wus Flak cor first?! AA; ‘5 “\1Nu MHZ sham/F . b MC!— a. ’N P” z mbozéw W aubc H'H’s army“); 1"; Snug Wit momwpx‘). Puma 2 S\¢\y\1k \A m A “Mi. e. (5 points) At first glance, the signal at 6 1.65 ppm appears to be a quintet. Given the structure that you deduced in part c, is this an accurate description of thevsignal? if not, what kind of multipiet is it (doublet. triplet, doublet of doublets, etc.)? Hp. ’Tlm‘s Pub Wu be as dawkbj a4? qutfld‘g v M \DQXIMM MM, 33‘» ‘5 wng Problem 6 (25 points). A compound with molecular formula CGH1003 has the 1H spectrum shown below. MN 1 Z W 30 20 10 0 HZ WM 5.15 5.10 5.05 500 L 1.45 1.40 1.35 1.00 l 2.20 215 2.10 l . r . I 10 9 8 7 6 5 4 3 2 1 D a. (4 points) You can deduce partial structures from several ofthe signals in the 1H NMR spectrum. What substructures account for the integration and multiplicity of the signals in the spectrum with the following chemical shifts? 61.40 ppm 65.07 ppm dig—cw» 07%— ‘ /+ at c. (8 points) The signal centered at 6 2.15 ppm appears to be a doublet with an integration of6, which may initially lead you to believe that there is an isopropyl group in the molecule. What evidence tells you that this signal does not arise from an isopropyl group? What substructure(s) does this signal correspond to? \{1 W1> W 2 W Mu‘t 'prbM “We. lS°\>n\o\%\ QM. “N womfié $44. 1 CorruP-Mknca 5(P-l—Lf “QED-HUS +9 17 R, “Hi WW“ Cf”. W \s M Swain stupid. W5 wx‘r in: 4h”, WIC’M \L'l' W A . “3'4? anyt— Problem 6 (continued): d. (7 points) What is the structure of this compound? jg Gil) Tim‘s wA +Mggk. ’WV. ‘30 “Mt Sure-8 “w 7. mi M “MA MI we 3M6 $\3'\‘)\\ m M 675% H15,» . W WNW: Parkmhrba ANA—t. \w «My-A 1\Sb \Alw baht-LA. MAM M! 6:70 is. .a M \r—tfiu vac; cu m M W4 “Jar PM? e. (6 points) The 13C NMR spectrum of the same compound is shown below. 205 4‘ 170231 l | 220 200 180 160 140 120 100 74 got —- 75 4‘2 — 20683 —~ 1% %4 80 60 4O 20 What substructures in the molecule give rise to the signals in the 13C NMR spectrum with the following shifts? 5 74.9 99m 0 L. /\\ T; \B/ 6170.2 ppm J, D 5 205.5 99m C) \\ we 3*» ...
View Full Document

This document was uploaded on 10/09/2008.

Page1 / 8

345 Exam 1 - Yoon - Key - Name: ‘ Student lD#: Exam 1 -...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online