KEY. Massachusetts Institute of Technology Organic Chemistry Hour Exam #1. Name (Please both print and sign your name)

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1 KEY Massachusetts Institute of Technology rganic hemistry 5.3 Friday, September 9, 006 Prof. Timothy F. Jamison our Exam # Name (Please both print and sign your name) fficial Recitation Instructor Directions: losed book exam, no books, notebooks, notes, etc. allowed. owever, calculators, rulers, and molecular model sets are permitted. Please read through the entire exam before beginning, in order to make sure that you have all the pages and in order to gauge the relative difficulty of each question. Budget your time accordingly. Show all your work if you wish to receive partial credit. You should have pages total: 8 exam pages including this page, pages of reference information, and blank pages for scratchwork. Question: Grader:. / 0 points. / 5 points 3. / 5 points. / 5 points 5. / 5 points Total: / 00 points

2 . (0 points total, points each) For each set of compounds below, circle the one in which the indicated hydrogen is the furthest upfield in a NMR spectrum. A. N Me 6.77 NMe 6.59 Both Awarded Full redit B. l3 l 3 l D. 3 3 ( 3 ) ( 3 ) 3 E. = Figure by MIT W.

3 . (5 points total) Answer the questions below about the structure that has the following data: EA, 66.6;,.8; N,.0 MW (g/mol) NMR (ppm) 0.3, 8.0,.7 IR (cm - ) 6 (strong more intense than the - stretches between 800 and 300); no other peaks between 500 and 000. NMR spectrum: 6, J=6.9 Z N = = N, J=6.9 Z ppm 0 Figure by MIT W. a. (3 points) To what structural fragment does the signature splitting pattern in the NMR correspond? ircle your final answer. 3 3 or = c-pr etc. 3 Figure by MIT W. b. ( points) Which peak or peaks in the 3 NMR correspond(s) to the fragment you identical in a, above. List the chemical shift(s) of the peak(s), and circle your final answer(s). 9.0,.7 Figure by MIT W. 3

4 c. (5 points) Determine the molecular formula of this compound. ircle your final answer. 7 N d. (5 points) alculate the Index of ydrogen Deficiency (ID) of this unknown compound. ircle your final answer. e. (0 points) Draw the structure of the unknown compound. ircle your final answer. N==N N N (Also full credit) Figures by MIT W.

5 3. (5 points total) Answer the questions below about the structure that has MW = 07 and the following NMR spectra: 6,s, J=7.9 Z, J=7.9 Z PPM PPM Figure by MIT W. 5

6 a. (0 points) Determine the molecular formula of this compound. ircle your final answer. 7 9 N.07 - DD # F N.NSIDER N:.07 - = 93 93/3 = 7 + /3 => 7 9 N b. (5 points) alculate the Index of ydrogen Deficiency (ID) of this compound. ircle your final answer. c. (0 points) Draw the structure of the unknown compound. ircle your final answer. Me N Me Figures by MIT W. 6

7 . (5 points total) An unknown compound (X) contains only carbon and hydrogen, has MW =, and exhibits the spectral data below. In addition to the IR signal listed below, there are only peaks corresponding to - stretches (between 3300 and 900) and several peaks in the fingerprint region. Please note that there are no overlapping peaks in either the NMR or the 3 NMR spectra. In other words, what you see is all there is! IR (cm - ) 5 3 NMR (ppm) 77.8, 70., 30. NMR (ppm).5 (s) When compound X was treated with excess n-buli (n-butyllithium) in tetrahydrofuran and then excess 3 I (iodomethane), a new compound (Y) with MW = 68 and signals in its 3 NMR spectrum was formed. What are the structures of X (5 points) and Y (0 points)? (Show your work in the space below for partial credit consideration.) Write your final answers in the boxes provided below.. n-buli ( 3 ) X. 3 I Y. n-buli (excess), TF. 3I(excess) X (MW=) Y (MW=68) Figure by MIT W.

8 5. (5 points) In one of our problem sets, cubane ( 8 8 ) was one of the possible answers to a structure elucidation problem. Based on the formula for the Index of ydrogen Deficiency, the ID of cubane is 5. owever, as you know, a cube has six sides. In other words, it looks like cubane has 6 rings and thus that its ID should also be 6. Please provide an explanation (not the formula used to calculate the ID) for this apparent discrepancy in the spaces below. EMIALY, AN D 5 "YDRGENATIN" RXNS T BTAIN "SATURATED" (AYLI, N T BND) BND : ID= REDRAW WIT DISTRTED - BNDS, VILA UBANE IS IN FAT A PENTAYLI MLEULES! 8 8 ID= ALS, AN DRAW AS UBE (BNDS -, RDER AT LEFT) AND SEE TAT DRAWING 5 RING GIVES UBANE Figure by MIT W.