2009_15_NMR spectroscopy [Compatibility Mode]

2009_15_NMR spectroscopy [Compatibility Mode] - Chem...

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Unformatted text preview: Chem 2204/2206/2208 Wednesday Mar. 18 Lecture 17 on NMR(I) TODAY! Friday Mar 20 Lecture 18 on NMR (II) Wednesday Mar 25 Lecture 19 on Stereochemistry (I) Friday Mar 27 Lecture 20 on Stereochemistry (II). 1 • Wednesday, April 1 Optional review lecture – go over sample Exam and problems; Exam topics etc. • Friday April 3 Lab Exam Theatre B 11:30 – 1.00 NMR spectroscopy Chapter 13 2 NMR Assignment 6 McMurry 6e, (7e) Topic Chapter Section Problems Introduction 13.1 Chemical shift 13.2-13.3 13.3, 13.4,13.5 Carbon 13 NMR 13.4, 13.5 13.6 , 13.8 , 13.32 roton NMR 3.8 3.11 3.14, 13.16 3.19, 3 Proton NMR 13.8-13.11 13.14, 13.16-13.19, 13.37( 38 ) TODAY • Intro to NMR (Slides 5 – 12). • Three fundamental NMR Parameters: 4 1. Chemical shift (ppm scale) 2. Intensity information 3. Nearest neighbour analysis • Problem Solving The World’s Premier Antifungal Drug How is the structure of this molecule determined? 5 1 H NMR spectrum of Amphotericin B methyl ester (Professor Jeff Manthorpe) The structure of amphotericin B is determined by NMR ! 6 Spectrum obtained for Professor Jeff Manthorpe NMR in CONTEXT: Information on molecular structure is typically obtained using ~ 4 routine spectroscopic methods: 1. UV-Vis (for conjugated systems). 7 2. IR (for certain functional groups). 3. Mass spectrometry (MS) (for molecular weight and the weight of fragments). C n H m OSNX 4. Nuclear magnetic resonance (NMR) gives detailed structural information (including Stereochemistry). O OH O H Organic Chemists mainly rely on two methods of NMR analysis • 1 H (proton (hydrogen) NMR) • 13 C (carbon NMR) – Note: 12 C nuclei not detected by NMR 8 • Also possible to detect: – 19 F, 14 N, 17 O, 2 H (D), 31 P *NMR observable nuclei have odd mass or odd atomic number, or both NMR “experiment” • In the presence of an applied magnetic field (B), NMR-active nuclei (e.g. 1 H) align their magnetic moment vectors ( μ ) with or pposed the field. 9 opposed to the field. B μ or This generates two spin states E 10 6 10 6 + 1 Small excess in lower state NMR instrument Spin 10 Note: MRI - magnet rotates; Sample is stationary Generate a 1 H or 13 C spectrum Intensity Observe Absorption of Rf energy ( Δ E) Δ E 11 B lo B hi B (magnetic field strength) ∆...
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This note was uploaded on 07/28/2009 for the course ORGANIC CH CHEM 2204 taught by Professor Dr.levin during the Winter '08 term at Indian Institute of Technology, Chennai.

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2009_15_NMR spectroscopy [Compatibility Mode] - Chem...

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