NMR - CFQ & PP: Proton NMR (1H-NMR) Spectroscopy...

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CFQ & PP: Proton NMR Spectroscopy 109 1 H-NMR) Spectroscopy Reading Brown and Foote: Sections 13.1 – 13.11, 13.14, 18.3B, 20.4 and 22.5 Lecture Supplement Proton Nuclear Magnetic Resonance Spectroscopy ( 1 H-NMR) (Page 25 of this Thinkbook) Optional Web Site Reading Nobel Prize in Chemistry 1991 (www.nobel.se/chemistry/laureates/1991/index.html) More on Spin Coupling (web.chem.ucla.edu/~harding/30C/30C_w03/NMRsupp.pdf) Suggested Text Exercises Brown and Foote: Chapter 13: 2 – 7, 10 – 13, 18 – 20, 22, 25, 27, 29, 31. Optional Interactive Organic Chemistry CD and Workbook Supporting Concepts: NMR Spectroscopy Tutorial (p. 76) Spectroscopy: 1 H-NMR topics (p. 47 – 53) Optional Web Site Exercises Webspectra (www.chem.ucla.edu/~webspectra) You do not need to memorize the typical proton chemical shifts as given in the lecture handout. This data will be given on an exam if needed. However you are expected to be intimately familiar with the structural features that influence chemical shift, and the use of chemical shift data to solve structure problems. More problems in which structures are deduced from NMR spectra are included with Concept Focus Questions 1. Clearly and concisely define each of the following terms. (a) Chemical shift (d) Spin - spin coupling (f) TMS (b) Downfield (e) Splitting (g) Upfield (c) NMR 2. Briefly explain at the atomic level the events that result in an NMR signal. 3. There are four basic types of information that can be obtained from an NMR spectrum. Briefly describe the significance of each of these four: Number of signals, relative position of signals, relative intensity of signals and splitting of signals. 4. Briefly discuss the concept of equivalent protons. Give a clear example of equivalent and nonequivalent protons.
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110 5. How does electronegativity influence chemical shift? 6. Compare the chemical shift of methane and ethane. Formulate a general rule that allows one to predict the relative chemical shift of the hydrogen atom in the series RCH 3 , R 2 CH 2 and R 3 CH. 7. Briefly explain the origin of splitting patterns and the n + 1 rule that allows us to predict these patterns. 8. What are the structural requirements for proton-proton spin coupling to occur? What structural features prevent the coupling? 9. Briefly explain why NMR signals for protons attached to oxygen and nitrogen are often broad. 10. What are the expected chemical shift ranges for vinyl and aryl protons? 11. Predict the proton NMR spectrum of 2-methylpropanol: OH 12. Deduce the structure of a compound of formula C 3 H 7 Br that has the following proton NMR spectrum: 3.1 ppm (triplet, integral = 1), 1.7 ppm (sextet, integral = 1), 1.0 ppm (triplet, integral = 1.5). Concept Focus Questions Solutions
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NMR - CFQ & PP: Proton NMR (1H-NMR) Spectroscopy...

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