Final Exam - 2003 - Chemistry 439 Final Exam Name Student...

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Unformatted text preview: Chemistry 439 Final Exam Name Student Number Short Answers: (30 points) 1. What is a typical geminal lH-IH coupling constant? 2. What is a typical vicinal 1H—‘H coupling constant? 3. What is the approximate lH-BC 1J coupling constant for an sp3 carbon? 4. Briefly describe the following two dimensional experiments: NOESY HMQC ZQF—COSY 5. Listed below are some fragments that are produced in a mass spectrum. Draw the structure of these fragments: 44 91 105 6a. If your lH frequency is 700 MHz, what is your carbon frequency? 6b. Karplus equations relate bond angle with coupling constants. What is the structural requirement in an organic molecule that would make these relationships useful (6 pts)? Suddenly. through [man not yet funy undemond. Darren ‘ Betty"! apartment became the center at a new black ink. Name 7. Propose a structure that is consistent with the following set of spectra. (12 points). IR spectrum (liquid film) 1670‘ 4000 3000 2000 1600 1200 800 V 15m“) 90 mass spectrum ‘2 ' .2 7 .5. I: ‘3 UV spectrum .5 0.764mg/10m1 Moon 1'; a 0.1cm cell 3 E 1.0cm cell ‘6 an w “mum—.mn—WWWH 0 40 60 80 100120" 160180 200 20 240 260 1 ‘ O m/e 20MB: carbon-13 NMR spectrum CDCl 3 solution _L_ off-resonance decoupled proton decoupled 100MHz proton NMR spectrum (mm.3 solution Name 8. (16 pts) The following 2D spectra are of Euplotin A. The first plots are a 700 ms mixing time NOESY experiment. The last spectrum is an HMBC experiment. The assignments and structure are shown below. Answer the questions listed below. H shift (ppm) #protons —_ —_ :- —|_ m_ _ :- I1— _ l!- _ _ 20.9 m— Unfortunately, the stereochemistry is not indicated for the protons on the ring except for proton b. You are to make the stereochemical assignments based on the observed NOEs in the following spectra. In other words, we do not know if the c, d, e, or f protons are pointing up or down as the structure is drawn. Also, g and g’ and h and h’ can have their stereochemistry assigned. Let us designate that g and h are pointing up and g’ and h’ are pointing down. Getting started and important hints (all numbers are in ppm): Note the NOEs between H5. and 5.92 (Hb), 2.52 (CH2 (n)), and 1.52 (CH2 (0)). This does not help us with the stereochemistry but it does give you an idea of the NOEs you can expect. On the first expanded plot, you will find H1, at 5.92 ppm. It shows (strong to medium) NOEs t02.70 (medium) and 2.03 (strong) and it does not show an NOE to 6.06 ppm. Based on this information, you now know the stereochemistry of He, Rd, and He. Hc up or down (circle correct answer)? Hd up or down (circle correct answer)? He up or down (circle correct answer)? To finish the stereochemical assignment of the methine protons, note the large NOE from Hc to 1.97 ppm. You may now assign Hf as up or down: Hf up or down? Now we must finish the assignments of g/g’ and h/h’. These methylenes are indicated on the second expanded plot with boxes. Follow the NOEs from Hd to get its closest proton neighbor at carbon h. Complete this process for Hg and Hg’ and fill in the assignments below: roton Chemical shifi . m 9. (4 pts) The HMBC of euplotin A is the last spectrum shown. The one bond correlation of the proton with its own carbon often shows up as a doublet and is drawn with a line or bracket in this spectrum. List the long-range correlations for Ha: 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1 .5 1.0 7.5 ppm 1.5 2.0 .- -F.‘J1.’-" K. 2.5 .. ..‘-. 3:.- ¢-.-u._’. sA- .. M‘s-t.- 3;...uov'ou .1 - fi"'- Inna . u'nlo'ul ran-nu. -. -- I; 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 ppm 1.0 1.5 H "Du-Ma --'-"~ «ah-s. ~ —.-....~~,-.w.-~l—. an. 4‘ --- -a.‘-o -.-rr- #.-’- 4.5 4.0 3.5 3.0 2.5 2.0 5.0 >— U) nu 0 2 U) .E .5 E U3 E O O h < .E E D. 3 I.“ 6.5 6.0 5.5 7.0 7.5 Enn— Fé N... 9—. «.9 m4 9+ h... w# m... c.N _..N N.N N.N ¢.N m.N 9N N.N N.N QN ed as as E 2 N.» as as as we 3 3 3 we in 3 3 ad 9o 3 3 3 $82 9:55 2: 2K < £855 3 _..F N.—. m... vé m; m4. 5% 9—. 0... ON .mN N.N N.N TN m.N m.N N.N w.N m.N chan 1.5 2.2 2.1 2.0 1 .9 1.8 1.7 1.6 2.3 2.4 2.5 2.6 2.7 ppmzs (3V. a @ Euplotin A 700 ms mixing NOESY M?) 7&7 15 1.6 17 1.8 . 9, , 3%.; m”, mflé‘fi ‘ 1.8 1.9 ~ 1.9 2.0 2.0 2.1 2.1 a! «'2 N N r) + , l‘l I'A\ «554mm 2.2 2.3 2.4 » k-IHIII. 2.4 2.5 I @111 2.6 ' WW V ‘1‘ 2.7 @o 1.00 UQAL .J ’3 I f a 1 2.8 ppm 2.6 2.5 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 1.5 2.7 2.8 can 8“ on our our cor omw oer Dew cup our nor cm on cm on c¢ av on ON D; 0.. 3.! 0.N 3.0 0.9 3.3 0.3 3.0 0.0 3.0 0.0 3. ~ 0. s ...
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This note was uploaded on 10/08/2009 for the course CHEM 439 taught by Professor Falzone,c during the Spring '08 term at Pennsylvania State University, University Park.

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Final Exam - 2003 - Chemistry 439 Final Exam Name Student...

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