12-23 An unknown, foul-smelling hydrocarbon gives the mass spectrum and infrared spectrum shown. (a) Use the mass spectrum to propose a molecular formula. How many elements of unsaturation are there? (b) Use the IR spectrum to determine the functional group(s), if any. (e) Propose one or more structures for this compound. What parts of the structure are uncertain? If you knew that hydrogenation of the compound gives n-octane, would the structure still be uncertain? (d) Propose structures for the major fragments at 39, 67, 81, and 95 in the mass spectrum 110 41 69 100 41 80 39 60 abundance 40 67 81 20 M' 95 0 10 019 20 30 40 50 60 70 80 90 mz 100 110 120 130 140 150 160 (continued Study Problems 603 25 100 3.5 4.5 wavelength (um) 5.5 6 9 10 11 12 13 14 15 16 80 60 40 20 0 4000 3500 3000 2500 1600 2000 1800 wavenumber (cm 1400 1200 1000 800 600