# tb12 - Chapter 12 - Structure Determination: Mass...

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Chapter 12 - Structure Determination: Mass Spectrometrv and Infrared Spectroscopv Select the most reasonable formula for the compounds with the following mass spectral data: 1. M+ at m/z = 101 with a minor M+ 1 peak a. CsH6Cl b. CSH12N2 c. C6H1sN d. C9H120 Answer: c 2. M+ m/ z = 136 and M+ at m/ z = 138 of approximately equal intensity a. C6H130Cl b. C4H9Br c. ClOH16 d. C9H120 Answer: b 3. The sugar glucose contains C, H, and 0 and has a mass of 180.0634 amu as determined by high-resolution mass spectrometry. Glucose contains an equal number of carbon and oxygen atoms. What is the molecular formula of glucose? CH = 1.00783 amu, 12C = 12.00000 amu, 160 = 15.99491 amu) Answer: Since the number of carbons and oxygens is equal, we can add the masses of C and 0 and then divide 180.0634 by that number. The remainder should be the number of hydrogens. 12.0000 + 15.99491 = 27.99491 180.0634 -;-27.99491 = 6 carbons and 6 oxygens with ~ 12 remaining So, the formula for glucose should be C6H1206. We can confirm this by doing the math. (6 x 12.0000) + (12 x 1.00783) + (6 x 15.99491) = 180.0634 Use the data below to answer the following questions. Loratidine is the active ingredient in the antihistamine Claritin@. Mass spectral analysis of loratidine shows M+ at m/z = 382 and M+at m/z = 384 in an approximate ratio of3:1 in intensity. 4. The mass spectral data indicates that loratidine contains: a. fluorine b. chlorine c. bromine d. iodine Answer: b 5. Loratidine is known to contain nitrogen. What is the minimum number of nitrogens in loratidine? Answer: Since the molecular ions are even numbers, loratidine must have an even number of nitrogen atoms. Therefore, the minimum number of nitrogen atoms in loratidine is two. Test Itemsfor McMurry's Organic Chemistry, Seventh Edition 101

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6. Which ofthe following statements best describes the base peak in a mass spectrum? Answer: a. b. c. d. The peak from the most stable radical. The peak from the species that has the isotope with the hightest atomic number. The peak of highest intensity. The peak from the molecule minus an electron. c For each compound below, what are the masses of the charged fragments produced by the indicated cleavage pathways? 7. Alphacleavageof ~ Answer: This compound, phenyl acetone, has the formula C9HlOO and a nominal mass of 134. cleavage will result in charged fragments at
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## This note was uploaded on 10/10/2011 for the course CHEMISTRY CHM2046 taught by Professor Johnston during the Spring '11 term at University of South Florida - Tampa.

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tb12 - Chapter 12 - Structure Determination: Mass...

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