Chapter 14, Problem 85CP

Predict the masses and the structures of the most abundant fragments observed in the mass spectra of the followingcompounds.(a) 2-methylpentane (b) 3-methylhex-2-ene (c) 4-methylpentan-2-ol(d) 2-methyl-1-phenylpropane

5. Mass spectra are provided for two constitutional isomers with the formula C10H14O. Predict the structures of each molecule. Label at least one fragment ion in each spectrum that helps elucidate its structure. Relative Intensity 120 100 80 60 20 0 120 100 80 60 40 10 20 ه 15 14 18718 19 26272829 27 29 i k 26 30 70 20 31 30 ..." 39 43 30 45 3638 40 42 44 4647 49 40 51 50 50 ܘܪܝܝܐ 00 | 830 کم میوه 2 کا 5758 60 60 65 70 78 79 777496 80 41 43 3940 6066264 | 3304 30000 142 | 40546 440*********** | 667 6807172784870700 88508780 363738 40 80 80 # m/z 90 m/z 89 91 90 93 94 98 100 . الی 100 105 10964 93 103 | 9495 9700 10002104080007 fois 110 110 117 115 118 113 119 120 120 132 131 133 12289 || 1395 130 121 1151617181920-122 126272829303132333435 130 140 140 14748 150 150 14485051 150 2

G.5 Mass spectra were acquired for 1,4-diethylbenzene and 1-methyl-4- propylbenzene. The base peak of spectrum A is at m/z = 105 and that of spectrum B is at mlz = 119. Match each spectrum to its compound.

The following two mass spectra represent 1-bromo-4-ethylbenzene and (1-bromoethyl)benzene, respectively. 100 - MS-IU-9451 Spectrum 1 80 - 60 40 20 - 25 50 75 100 125 150 175 m/z 100 - MS-NU-8350 Spectrum 2 80 - 60 20- 20 40 60 80 100 120 140 160 180 200 m/z 1. Assign each spectrum to one compound 2. Justify your assignment by assigning relevant signals in each spectrum. 3. Explain how you could determine which spectrum belongs to which compound. Relative Intensity Relative Intensity

The mass spectrum of 2,3-dimethylpentane also shows peaks at mlz = 57 and 43. Propose possible structures for the ions that give rise to these peaks.

The proton NMR and C-13 NMR for a compound with the molecular foromula C5H10Br2 are shown below. Determine the structure of the compound. In the proton NMR: Doublet at 1.7 ppm. Intensity = 3 Singlet at 1.8 ppm. Intensity = 6. Quartet at 4.1 ppm. Intensity = 1.

The data is for the molecular formula C8H8O3 (vanillin) with a mass of 152. Analyze the Mass spec data (include a table listing the molecular ion, base peak, and any other relevant fragments) – also include structures of fragments.

2-Methylpentanal and 4-methyl-2-pentanone are constitutional isomers with the molecular formula C,H,,0. Each shows a molecular ion peak in its mass spectrum at mlz 100. Spectrum A shows significant peaks at mlz 85, 58, 57, 43, and 42. Spectrum B shows significant peaks at mlz 71, 58, 57, 43, and 29. Assign each compound its correct spectrum. `H 2-Methylpentanal 4-Methyl-2-pentanone

Hydrohalic acids (i.e., HCl, HBr, HI) add to the double bond of alkenes to yield alkyl halides. Shown below is the carbon NMR spectrum of an alkene of formula C5H10. What is the structure of this alkene?