1 ppm 41 ppm 15 ppm 12 ppm 02 ppm and 00 ppm not all

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shift choices: 7.1 ppm, 4.1 ppm, 1.5 ppm, 1.2 ppm, 0.2 ppm, and 0.0 ppm. Not all the choices will be used, and each choice cannot be used more than once . CH 4 CH 3 F CH 3 CH 2 F CH 3 CH 2 OH (CH 3 ) 4 Si 15. (4) In each box draw an isomer of C 6 H 6 other than benzene that has the required number of signals in its 1 H- NMR and 13 C-NMR spectra. If a corresponding structure is not possible, write ‘not possible.’ Two 1 H-NMR signals and two 13 C-NMR signals. One 1 H-NMR signal and three 13 C-NMR signals. 16. (2) Of the molecules shown below, circle the molecule that is the best fit for this 13 C-NMR spectrum: 153 ppm (singlet), 135 ppm (singlet), 130 ppm (doublet), 115 ppm (doublet), 37 ppm (triplet), 25 ppm (triplet), and 14 ppm (quartet). 17. (4) Answer each question by writing one word in each blank. (a) In an early but very important application of x-ray crystallography, the Braggs measured (for the first time) carbon-carbon bond lengths and carbon-carbon-carbon bond angles in a substance called _______________. (b) Rosalind Franklin verified that DNA is a helical molecule when she saw a(n) _________________ pattern in photo 51, one of many DNA diffraction patterns produced by x-ray crystallography. OH OH OH O
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Chemistry 14C Fall 2009 Exam 2 Page 4 Page 4 score = 18. (9) Draw in the box a molecule that is consistent with the given molecular formula, IR, and NMR data. Use the back of the spectroscopy data page, or back of the previous exam page, for scratch paper if needed . (a) Formula : C 4 H 8 O IR : C=O @ 1718 cm -1 1 H-NMR : 2.45 ppm (quartet; integral = 1), 2.14 ppm (singlet; integral = 1.5), and 1.06 ppm (triplet; integral = 1.5) 13 C-NMR : 209 ppm (singlet), 37 ppm (triplet), 29 ppm (quartet), and 8 ppm (quartet) (b) Formula : C 4 H 8 O IR : C=O @ 1728 cm -1 1 H-NMR : 9.76 ppm (triplet; integral = 1), 2.37 ppm (quartet; integral = 2), 1.64 ppm (sextet; integral = 2), and 0.97 ppm (triplet; integral = 3) 13 C-NMR : 203 ppm (doublet), 46 ppm (triplet), 16 ppm (triplet), and 14 ppm (quartet) (c) Formula : C 4 H 8 O IR : No C=O or OH 1 H-NMR : 3.73 ppm (triplet; integral = 1) and 1.84 ppm (triplet; integral = 1) 13 C-NMR : 68 ppm (triplet) and 26 ppm (triplet)
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