Combined Spectroscopy

Combined Spectroscopy - CFQ & PP: Solving Combined...

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134 Reading Brown and Foote: Section 13.15 Lecture Supplement Solving Combined Spectroscopy Problems (page 39 of this Thinkbook) Suggested Text Exercises Brown and Foote: Chapter 13: 2 – 7, 10 – 13, 18 – 22, 25, 27, 29, 31. Optional Interactive Organic Chemistry CD and Workbook Comprehensive Spectroscopy Questions (p. 63) Concept Focus Questions There are no Concept Focus Questions specifically for this material. Refer to the CFQs for spectroscopy units covered previously in lecture. Practice Problems Solving problems is critical to success in mastering organic chemistry. This is especially true when studying fundamentals of spectroscopy. There exist a number of excellent compilations of spectral problems for the undergraduate. You are encouraged to try some problems from each site listed below. WebSpectra (http://www.chem.ucla.edu/~webspectra/): A project of Professor Craig Merlic at UCLA. Each problem consists of a formula, 1 H-NMR, and 13 C-NMR. Some problems have IR, DEPT, or 2D-NMR spectra as well. You will need to measure the heights of each portion of the integrals of the 1 H-NMR spectrum; no numbers are given. The structural solution for each problem is given. Organic Structure Elucidation Workbook (http://www.nd.edu/~smithgrp/structure/ workbook.html): A project of Professor Bradley Smith at the University of Notre Dame. Each problem consists of a mass spectrum, IR, 1 H-NMR, and 13 C-NMR. The mass spectrometry data is not presented in tabular form, so it may be difficult to get accurate abundance data for the M, M + 1, and M + 2 peaks. In the real world, or on a Chem 14C exam, the data will be presented in a tabular form, allowing for precise determination of the M + 1 and M + 2 abundances. The answers are not given with the problems, so you can't cheat. Feel free to bring your answers to Dr. Hardinger to be checked. On past Hardinger exams, a correct answer for a combined spectral problem was worth full credit, usually about 35 points. If the answer was incorrect, analysis of the spectra may have been worth significant partial credit, so practice showing your work clearly and in a logical order.
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CFQ & PP: Solving Combined Spectroscopy Problems 135 1. Deduce the structure that corresponds to this spectral data. Mass spectrum: M: m/z 148 (100 %); M + 1: m/z 149 (11.25 %); M + 2: m/z 150 (0.54 %). IR: 1 H-NMR: 7.5 - 8.0 ppm (multiplet, integral = 2.5), 3.0 ppm (triplet, integral = 1), 1.8 ppm (sextet, integral = 1), 1.0 ppm (triplet, integral = 1.5). 13 C-NMR (DEPT): 200.4 ppm (singlet), 137.0 ppm (singlet), 132.8 ppm (doublet), 128.5 ppm (doublet), 128.0 ppm (doublet), 40.4 ppm (triplet), 17.7 ppm (triplet), 13.8 ppm (quartet).
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136 2. Provide a molecular structure that is consistent with the spectral data. Mass spectrum: M: m/z 132, 100%; M + 1: m/z 133, 6.89%; M + 2: m/z 134, 1.42%.
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This note was uploaded on 03/09/2010 for the course CHEM 30B Chem 30B U taught by Professor Miguelgarciagaribay during the Summer '10 term at UCLA.

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Combined Spectroscopy - CFQ & PP: Solving Combined...

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