11-StructureDetStrategy - 1. Identify functional groups...

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Structure Elucidation Strategy A. Molecular Formula: 1. Determine empirical formula using elemental analysis – usually, this is given . See pages 70-71 in Loudon if you would like to review how this works. 2. Use mass spectrometry to convert empirical to molecular formula. Molecular ion = parent ion = highest m/z = fragment resulting from loss of an electron = molecular weight of the parent molecule. Base peak = ion of greatest relative abundance – major fragment – gives some information about structure. 3. Use molecular formula to determine the units of unsaturation from molecular formula = rings + pi-bonds (review – page 126 Loudon). B. Functional Groups:
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Unformatted text preview: 1. Identify functional groups using IR and 13 C NMR (and sometimes 1 H NMR) Memorize the following IR stretches: 2. Determine symmetry by comparing 13 C NMR to molecular formula C. Connectivity 1. Identify molecular fragments using data from 1 H NMR: a. spin-spin splitting (identify number of neighboring H) b. integration (identify number of chemically equivalent H responsible for peak) c. chemical shift (Identify proximity to electronegative groups and/or functional group class by comparing ppm values to tables.) d. MS fragmentation 2. Assemble fragments 3. Confirm structural assignment – should be consistent with all data....
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This note was uploaded on 05/13/2010 for the course CHEM 151L taught by Professor Roy,christopher during the Summer '08 term at Duke.

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