Additional Questions - Chapter 13 1. A compound with molecular formula C12H24 exhibits a 1H NMR spectrum with only one signal and a 13C NMR spectrum with two signals. Deduce the structure of this compound. 2. An unknown compound, A (C7H10), shows four absorptions in its 13C-NMR spectrum, at 22 (CH2), 24 (CH2), 124 (CH) and 126 (CH) . On reaction with excess H2 and a Pt catalyst, A produces B (C7H14). B shows a single peak at 28.4  in its 13C-NMR spectrum. Ozonolysis of A gives C2H2O2. Suggest structures for A and B. 3. Hexamethylbenzene undergoes free-radical chlorination to give one monochlorinated product (C12H17Cl) and four dichlorinated products (C12H16Cl2). These products are easily separated by GC-MS, but the dichlorinated products are difficult to distinguish by their mass spectra. Draw the monochlorinated product and the four dichlorinated products, and explain how 13C NMR would easily distinguish among these compounds. 4. Low molecular weight esters (RCO2R) often have characteristic odors. Using its molecular formula and 1H NMR spectral data, identify each ester. a) Compound A, the odor of banana: C7H14O2; 1H NMR: 0.93 (doublet, 6H), 1.52 (multiplet, 2H), 1.69 (multiplet, 1H), 2.04 (singlet, 3H), and 4.10 (triplet, 2H) ppm. b) Compound B, the odor of rum: C7H14O2; 1H NMR: 0.94 (doublet, 6H), 1.15 (triplet, 3H), 1.91 (multiplet, 1H), 2.33 (quartet, 2H), and 3.86 (doublet, 2H) ppm. 5. Compound K, molecular formula C6H14O, readily undergoes acid-catalyzed dehydration when warmed with phosphoric acid to give compound L, molecular formula C6H12, as the major organic product. The 1H-NMR spectrum of compound K shows signals at  0.90 (t, 6H), 1.12 (s, 3H), 1.38 (s, 1H), and 1.48 (q, 4H). The 13C-NMR spectrum of compound K shows signals at  72.98, 33.72, 25.85, and 8.16. Deduce the structural formulas of compounds K and L. 6. Propose a structure for the compound that has the following spectra: NMR:  1.28 (3H, t, J= 7Hz);  3.91 (2H, q, J= 7Hz);  5.0 (1H, d, J= 4 Hz);  6.49 (1H, d, J= 4 Hz) IR: 3100, 1644 (strong), 1104, 1166, 694 cm-1 (strong); no IR absorptions in the range 700-1100 cm-1 or above 3100 cm-1 Mass spectrum: m/z =152, 150 (equal intensity); double molecular ion) 7. You are given three bottles containing o-dichlorobenzene, m-dichlorobenzene and p-difluorobenzene, along with broad-band decoupled 13C NMR spectra of the three compounds. Assign the three spectra to the three compounds and explain your reasoning. A: d 127.0, 128.9, 130.6, 135.1 ppm. B: d 127.7, 130.5,132.6 ppm. C: 116.5, 159.1 ppm.8. The proton NMR spectra of several C5H10Br2 isomers are summarized below. Deduce the structure of each compound. (a) , 1.0 (s, 6H); 3.4 (s, 4H) (b) , 1.0 (t, 6H); 2.4 (quart, 4H) (c) , 0.9 (d, 6H); 1.5 (m, 1H), 1.85 (t,2H); 5.3 (t, 1H) (d) , 1.0 (s, 9H); 5.3 (s, 1H) (e) , 1.0 (d, 6H); 1.75 (m, 1H); 3.95 (d, 2H); 4.7 (quart, 1H) (f) , 1.3 (m, 2H); 1,85 (m, 4H), 3.35 (t, 4H) 9. Label each set of chemically equivalent protons, using a for the set that will be at the lowest frequency (farthest upfield) in the 1H NMR spectrum, b for the next lowest, and so on. Give the multiplicity of each signal. 10. Each of the following compounds is characterized by a 1H NMR spectrum that consists of only a single peak having the chemical shift indicated. Identify each compound. a) C8H18;  0.9 b) C5H10;  1.5 c) C8H8;  5.8 d) C4H9Br;  1.8 e) C2H4Cl2;  3.7 f) C2H3Cl3;  2.7 g) C5H8Cl4;  3.7 h) C12H18;  2.2 i) C3H6Br2;  2.611. Are bicyclic compounds A and B shown below readily distinguished by their proton-decoupled 13C NMR spectra? Would DEPT spectra be of use in solving this problem? 12. How many signals would each compound give in its 1H NMR spectrum? a) Etane b) Propane c) tert-Butyl methyl ether d) 2,3-Dimethyl-2-butene e) (Z)-2-Butene f) (E)-2-Butene 13. Assign the 1H NMR spectra of the compounds and explain the multiplicity of the signals. (a) H 0.97 (3H, t, J 7 Hz), 1.42 (2H, sextuplet, J 7 Hz), 2.00 (2H, quintet, J 7 Hz), 4.40 (2H, t, J 7 Hz) (b) H 1.08 (6H, d, J 7 Hz), 2.45 (4H, t, J 5 Hz), 2.80 (4H, t, J 5 Hz), 2.93 (1H, septuplet, J 7 Hz) (c) H 1.00 (3H, t, J 7 Hz), 1.75 (2H, sextuplet, J 7 Hz), 2.91 (2H, t, J 7 Hz), 7.4-7.9 (5H, m) 14. 2-methylpentane, 3-methylpentane, and 2,3-dimethylbutane are isomeric hydrocarbons; 13C nuclear magnetic resonance spectral data for the compounds are given below. Isomer 1:  19.5, 34.0 Isomer 2:  11.4, 18.8, 29.3, 36.4 Isomer 3:  14.3, 20.6, 22.6, 27.9,