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Identification of Organic Compounds by GC/MS, IR & NMR

Identification of Organic Compounds by GC/MS, IR & NMR. Marcela James. Overview. Before Staring… GC/MS Definition, procedure GC/MS for organic unknown Infrared Definition, procedure Infrared for organic unknown Molecular Formula NMR Definition, procedure, NMR for organic unknown

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Identification of Organic Compounds by GC/MS, IR & NMR

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  1. Identification of Organic Compounds by GC/MS, IR & NMR Marcela James

  2. Overview • Before Staring… • GC/MS • Definition, procedure • GC/MS for organic unknown • Infrared • Definition, procedure • Infrared for organic unknown • Molecular Formula • NMR • Definition, procedure, • NMR for organic unknown • Organic Unknown Identity • References • Questions

  3. Before Staring… • Industry: Team work • Processes: Identify subproducts • Is the compound pure? • Run a GC, only one major peak • Is ultimate analysis available? • %C • %H • %N • %S • %P • %Halogens http://ec.europa.eu/environment/chemicals/images/chemicals.jpg

  4. Gas ChromatographyMass Spectrometry • Finds molecular weight • Separation on mass/charge ratio • Mass/charge “unit” is recorded as a spectrum • Types of GC/MS • Electron Impact Ionization • Chemical Ionization http://www.hood.edu/images/content/academics/instruments.JPG

  5. Gas ChromatographyMass Spectrometry • 15 CH3 • 18 H2O • 28 CH2=CH2 • 46 NO2 • 77 • 92 -CH3 • Is the parent ion peak present? • Last important peak • Halogens or sulfur present? • Look at M+2 peaks • Nitrogen present? • Odd molecular weight • Common fragmentations?

  6. GC Organic Unknown Abundance 6.84 Time (min)

  7. MS Organic Unknown 106 107 CH3- -NH Parent Ion Peak There is presence of Nitrogen 77 28 91 15 13 39 52 65 Abundance CH3 CH2=CH2 m/z

  8. Infrared Spectroscopy • Identifies functional groups • Infrared region from 13000cm-1 to 40cm-1 • Liquids in sodium chloride cells • Solids in: • Solution with solvent • Nujol mull (mineral oil) • KBR solid disk http://www.chem.tsukuba.ac.jp/teranisi/images/apparatus/FTIR.jpg

  9. Infrared Spectroscopy • Is a carbonyl group present? (1820-1660cm-1) If present look for: • Acids, OH(3400-2400cm-1) • Amides, N-H(~3400cm-1) • Esters, C-O(1300-1000 cm-1) • Anhydrides, C=O(1810-1760cm-1) • Aldehydes, C-H(2859 & 2750cm-1) • Ketones, eliminate previous five choices

  10. Infrared Spectroscopy • IF carbonyl (C=O) is absent: • Alcohols, O-H(3400-3300cm-1) • Amines, N-H(~3400cm-1) • Ethers, C-O(1300-1000cm-1) • Double Bonds, Aromatic Rings: • Double bondC=C, (~1650cm-1) • Aromatic, C=C(1600-1450cm-1) http://www.ewels.info/img/science/molecules/benzene.jpg

  11. IR Organic Unknown No carbonyl C-H aromatic C-CH3 methyl N-H amine C=C ring stretch Transmittance Wavenumber

  12. Molecular Formula For the 3 double bonds and the ring structure • Organic compound definitely has: • A nitrogen (as an amine) • A ring (aromatic) • A molecular weight of 107 • Possible molecular formulas: • C6H7N2 • C7H9N • Double Bond Equivalent: • DBE= C - H/2 + N/2 - X/2 + 2 • DBE= 7- 4.5 + 0.5 +2 = 4

  13. Nuclear Magnetic Resonance • Locations of carbons and hydrogens • Sample absorbs electromagnetic radiation • Solvent peaks appear in the NMR spectra • Species have to be magnetically active: • 13C instead of 12C • 1H instead of 2H http://www.pharmacy.arizona.edu/yanglab/NMRFacility/NMR.JPG

  14. 1H NMR O -C-H • Solvent peaks: • TMS: (Si(CH3)4) 0ppm • Chloroform: (CDCl3) 7.2ppm • Acetone: 2.1ppm • Look for obvious chemical shifts: O-CH3 X-C-H -C C-H -H -COOH C=C-H N-H CH3 ppm

  15. 1H NMR for Organic Compound CH3 H H NH2 H H

  16. 13C NMR C-Cl, C-Br -C=C- -C C- O O CH3 CH2 -C-O- -C-OH -C-H ppm • Solvent Peaks: • Dichloromethane: (CHDCl2) 53ppm • Chloroform: (CDCL3) 77ppm • Acetone: (C3OH6) 205ppm • Look for obvious chemical shifts:

  17. 13C NMR Organic Compound 1 6 4 2 6 2 5 5 3 4 3 1 C-CH3 CH3 C-NH2

  18. The Organic unknown is… NH2 CH3 • m-Toluidine • m-Aminotoluene • ρ=107.17 g/mol • BP: 203°C • Carcinogen One million pounds produced annually in the U.S.

  19. References • Silvertein Robert M. Webster, Francis X. Kiemle, David J. Spectrometric Identification of Organic Compounds, 2005. State University of New York. John Wiley and Sons • Spectral Database for Organic Compounds (SDBS), National Institute of Advance Industrial Science and Technology (AIST), Japan. Website:

  20. Questions ? ? ? ? http://www.wpclipart.com/cartoon/more_cartoons/Mad_scientist.png

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