有機化學第12ç« ï&f

有機化學第12ç« ï&f

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2009/1/8 1 12. Structure Determination: Mass Spectrometry 質譜儀 and Infrared Spectroscopy 紅外線光譜 Based on McMurry’s Organic Chemistry , 7 th edition Determining the Structure of an Organic Compound
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2009/1/8 2 Determining the Structure of an Organic Compound ± Mass spectrometry (MS) 質譜儀 ± Infrared (IR) spectroscopy 紅外線光譜 ± Ultraviolet-visible spectroscopy (VIS) 紫外 - 可視光譜 ± Nuclear magnetic resonance spectroscopy (NMR) 核磁共振光譜 What can we have from … ± Mass spectrometry (MS) What size and formula? 大小與反應式 ± Infrared (IR) spectroscopy What functional groups are present? 官能基 ± Ultraviolet-visible spectroscopy (VIS) Is a conjugated π electron system present? 共軛雙鍵 ± Nuclear magnetic resonance spectroscopy Nuclear magnetic resonance spectroscopy What carbon-hydrogen framework is present? 碳氫關係
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2009/1/8 3 Why this Chapter? ± Finding structures of new molecules synthesized is critica synthesized is critical ± To get a good idea of the range of structural techniques available and how they should be used 5 OUTLINE ± Mass Spectrometry (MS) 質譜儀 of Small Molecules: Magneti -Sector Instrument Molecules: Magnetic Sector Instruments ± Interpreting Mass Spectra ± Mass Spectrometry of Some Common Functional Groups ± Mass Spectrometry in Biological Chemistry: Time-of-Flight (TOF) Instruments
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2009/1/8 4 OUTLINE ± Spectroscopy and the Electromagnetic Spectrum ± Infrared Spectroscopy ± Interpreting Infrared Spectra ± Infrared Spectra of Some Common Functional Groups 12.1 Mass Spectrometry of Small Molecules: Magnetic-Sector Instruments Sample vaporized and subjected to bombardment by electrons that remove an electron Fragment 碎片 Creates a cation-radical 8 Bonds in cation radicals begin to break (fragment) Charge to mass ratio is measured (m/z)
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2009/1/8 5
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2009/1/8 6 The Mass Spectrum Parent peak Unfragmented cation radical
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2009/1/8 7 Propane CH 3 CH 2 CH 3 The tallest peak Base peak Fig. 12.2 Molecular ion, M + Parent peak Fig. 12-2, p. 411 Other Mass Spectral Features If parent ion not present due to electron bombardment causing breakdown, bombardment causing breakdown, “softer” methods such as chemical ionization are used 2,2-dimethylpropane Fig. 12.3
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2009/1/8 8 12.2 Interpreting Mass Spectra ± Molecular weight from the mass of the molecular ion ± Doubl -focusing instruments provide high-resolution Double focusing instruments provide high resolution “exact mass” ± 0.0001 atomic mass units – distinguishing specific atoms ± Example MW “72” is ambiguous: C
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This note was uploaded on 11/11/2010 for the course CHE CH2005 taught by Professor 曹恒光 during the Spring '10 term at National Central University.

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有機化學第12ç« ï&f

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