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s03Exam1_Solutions - 1(10 pts The following compound called...

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Unformatted text preview: 1. (10 pts) The following compound called 18-annulene has an unusual 1H NMR spectrum with protons resonating at 8.9 ppm and —l.8 ppm. Suggest an explanation for this result. / v H Hike. l/Qw,:yv,wh 4: 3 . rum L.%“""‘if’\§" 3 . a" kidding} r"4j-L$V3'$L'i’r”:j ‘f “.1 " .1" . , p, . V 1’2 ‘m" Gus? “whiting + l {w- 3.»? " an...” c. I 3 so? {KPifigw‘ug‘j in”; m) sissfiim ‘I' ‘21 kr‘" 5: 5..., IN!" ”Emit! , Wm WK 5!“ MI} 2W“! if... R'L‘g) "’ 5 &$;|jflr‘wi? sag"; k, i ‘g a" “if Vtak V thug. {,F’ 4;»! Qarw'oukjy“ é... . J . . 3 fl“ {an . a1- airwyizéézat‘ *1 4:9 * {ME Curmuw” *4" i1: “*3 ' 3'“‘"”4‘ MC 2. (18 pts) The compounds, 5-methyl—3-hexanone, heptyl aldehyde, and 4,4—dimethyl-2-pentanone all have a parent ion of M+=114. Based upon their fragmentation patterns assign the following mass spectra (next page) to the proper member of this family of compounds. Show detailed (curved arrow) mechanisms for the diagnostic fragmentations upon which you are basing your answer. Do not try to assign all of the fragments. + Z {« Alhmbf; “EDJYCKK 1C? 42*: < U (7"?) (5m; $\> -\_ *6)! m‘ 33‘ “364“”? +1 2601 CONCCA' 4V) 61:0 ‘ “W04 —\ b: wrong ““0“: Spectra for QuestionZ +02 ,8“ gun/on r: $ch w; 4miv’w ”7. £0“ ”EFP'U ”AC4 break 0\/\ (AM $3341 6& L11 X kxm'an) 100 on O an 0 Relative Intensity A O 20 Relative Intensity a. O 100 on O 0'! O A O Relative Intensity 20 3. (16 pts) (a) Rank the following alkenes in terms of their C=C stretching frequencies. Explain your ranking. 1: Lowest wavenumber | l" pom 9912 6:01) 0mm \ “1 0091mm; (‘1) | . +1 72,6th 7 as \ . + 1 isoLA‘reb 7£0N>06mED ‘ + {L Home mewoeo copwmmu ' ON 1 ~ 1 ® 1 4 + V3 Q 1 6mm; HQflJA‘TIDW (b) Rank the following acetylenes in terms of the strength (intensity) of their CEC stretching absorptions in the IR. Explain your ranking. 1: Most absorbing CH3 COgMe CH3 CH3 COZMC ’ COzMC 3. (16 pts) (a) Rank the following alkenes in terms’of their C=C stretching frequencies. Explain your ranking. 1: Lowest wavenumber mm (b) Rank the following acetylenes in terms of the strength (intensity) of their CEC stretching absorptions in the IR. Explain your ranking. 1: Most absorbing CH3 cone 4. (16 pts) Briefly describe the principles used in ion mobility explosive detectors used in airports. Explain the mechanism of detection of explosives such as TNT and RDX. Are the ions of nitro compounds the same types as typical of most organics? Explain. OzN No2 TNT No2 NTNWN. OM/V\ RDX lag alum/9C Cl) alga) 199/13 “‘ L/pfs“ (,7 C7 (J (Li, I :11" LL f[( \L CNS: $3613, # 4/1 )75“; {(L£lelcl'<)L rl (Lylfll’tld /J ,5 Tm C; A? {— {:3 lll” m algss ”1/?” I) I H ’ ‘ ' ' “ /‘, lfiC‘C-‘i c a Ll L111; lcm 2.73 {We 1 7+ ‘2» pts T //: (:2 %’A6‘/ /r R! / L / ,,__1/ ' P z/‘V L l +- \ ,._ ./ b! NW 19 I o \G 3 5. (24 pts) Compound A (F.W.=98.1) when treated with Cr031pyridine gives compound B with a F.W.= 96. Provide the structures of A and B and your reasoning for the structural assignment. IR, 13C-NMR (decoupled), 1H—NMR of Compound A. OH fl ‘v*— r‘1 ~C “22% I PT" ‘ L —~‘ r (7 V ‘ 1 1 , ~ 1"»,\iii:<~k< L'H _._.':> \ (7+ 6 119' 1 C. W Lang; r.--._-._,\ g") ‘ i ! Q r\ \' it” L; C : 17‘ 'NHLGvuI L 2peaks : A * A ”L1 1 ‘ [ "xi. 1“ L % 33"?) 20(1-“14120 ‘60 140 120 1:1“ 80 50 40 20 0 '1‘ , , l. ( >‘ ,(v " 3 R, 13C-NMR (decoupled), 1H-NMR of Compound B. K" \ b b )7 .. r} '"“ » T2 A .T (W! “W 200 130 180 140 120 we so so 4o 20 o L_.,_,.._,__.._1...,_T__,_1_fl_._'_,.—r_,_T_—,_r_ ms-x 1-74: mm 9 8 7 S S 4 3 Z 1 0 6. (16 pts) The following 1H—NMR (taken at 300 mHz) spectra are for the compounds shown. Assign the spectra to the proper compounds and all of the resonances to the specific proton(s). Explain your reasoning. O \/“\ 1* “MK/k) 9/ QWV \ OCH2CH3 \/0\ (l Sililfiflwhf 9‘5; SW71, {/1 CHZCH3 ( 3 ( Q/ngvflj )7“ /\/\‘lfN ly/ L95?" (9“ WW I ~ "1 l a , ,4 :‘i’r’v “it ma 2»15<’1../4/2/h1b/ f‘, i ,W ,W , if: t mm; W w {1/ € [IO/ti; A. (I: Q) {If fl/ytflf'fi/j _, urn-02418 ppm 10 9 8 7 6 5 4 3 z 1 0 HPH-QPZSII ppm ...
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