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Chem 440/540 Advanced Organic Spectroscopy Introduction

Chem 440/540 Advanced Organic Spectroscopy Introduction. What spectroscopic techniques would be useful in determining the structure of this compound? H-1 NMR C-13 NMR 2D NMR (COSY and HETCOR) Mass spec (MS) Infrared (IR) Other: Index of hydrogen deficiency (IHD).

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Chem 440/540 Advanced Organic Spectroscopy Introduction

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  1. Chem 440/540 Advanced Organic Spectroscopy Introduction • What spectroscopic techniques • would be useful in determining • the structure of this compound? • H-1 NMR • C-13 NMR • 2D NMR (COSY and HETCOR) • Mass spec (MS) • Infrared (IR) • Other: Index of hydrogen deficiency • (IHD)

  2. H-1 NMR Spectrum

  3. C-13 NMR Spectrum CDCl3

  4. General Principles of Absorption Spectroscopy • A spectroscopic transition converts a molecule from a lower to a higher energy state. • E = h • = frequency of the electromagnetic radiation h = Planck’s constant  = c c = speed of light E = h = hc/

  5. Types of Spectroscopy

  6. Index of Hydrogen Deficiency (IHD) The degree of unsaturation can be calculated for any organic compound containing C, H, N, O, S, or the halogens. Use three steps: 1. Using the molecular formula, replace all halogens with hydrogens. 2. Remove all oxygen and sulfur atoms. 3. For each nitrogen remove the nitrogen and one hydrogen. The molecular formula is now reduced to CnHm IHD = n - m/2 + 1

  7. Calculate the IHD for each of the following molecules: • -sitosterol: C29H50O • 3-iodothiophene: C4H3IS • 5-iodouridine: C9H11IN2O6 • Chloramphenicol: C11H12Cl2N2O5

  8. Steps in Determining a Molecular Structure • Determine the molecular formula (MS). • Calculate the IHD. • Identify the functional groups (IR, NMR, UV). • Establish proton connectivities (1H-NMR) • Establish carbon connectivities (13C-NMR). • Determine the positions of functional groups on the carbon framework (IR, NMR, UV). • Confirm the structure by synthesis or X-ray diffraction.

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