Of mass spectra 25 mass spectra

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Unformatted text preview: •  moderate peak at m/z = 86: CHM3122 Interpreta$on of mass spectra 42 Mass spectra of some classes of compounds: rules and examples 22. aromaEc amides CHM3122 Interpreta$on of mass spectra 43 Mass spectra of some classes of compounds: rules and examples 23. aliphaEc nitriles • base peak at m/z = 97 is common for linear nitriles of 8 C’s or greater • cleavages of each C ­C bond gives peaks at m/z = 40, 54, 68, 82… due to (CH2)nCN+ ions CHM3122 Interpreta$on of mass spectra 44 Mass spectra of some classes of compounds: rules and examples 24. aliphaEc nitro compounds •  odd molecular ion peak is weak or absent •  m/z 30 peak for NO+ •  m/z 46 for NO2+ 25. aromaEc nitro compounds •  odd molecular ion peak is prominent •  peaks due to loss of NO2• (M ­46) •  peak due to the forma$on of the phenoxy ca$on (M ­30) CHM3122 Interpreta$on of mass spectra 45 Mass spectra of some classes of compounds: rules and examples 26. aliphaEc nitrites •  odd molecular ion peak is weak or absent •  peak at m/z = 30 (NO+) •  peak at m/z = 60 (CH2=+ONO) 27. aliphaEc nitrates •  odd molecular ion peak is weak or absent •  base peak due to the cleavage of the C ­C bond next to the ONO2 group, with the loss of the alkyl group agached to the alpha carbon •  peak at m/z 46 is also prominent (NO2+) CHM3122 Interpreta$on of mass spectra 46 Mass spectra of some classes of compounds: rules and examples 28. sulfur compounds •  the contribu$on of 34S isotope to the M+2 peak can help iden$fy these compounds 29. thiols •  characterisi$c ion m/z 47 (CH2=SH+) •  loss of HS (peak at M ­33) •  peak at m/z 89 : CHM3122 Interpreta$on of mass spectra 47 Mass spectra of some classes of compounds: rules and examples 30. aliphaEc sulfides •  visible molecular ion peak •  RCH=SH+ ion CHM3122 Interpreta$on of mass spectra 48 Mass spectra of some classes of compounds: rules and examples 32. aliphaEc chlorides, bromides, iodides •  Table 1.5 •  Figure 1.29 CHM3122 Interpreta$on of mass spectra 49 Mass spectra of some classes of compounds: rules and examples 32. aliphaEc chlorides, bromides, iodides •  Table 1.5 •  Figure 1.29 CHM3122 Interpreta$on of mass spectra 50 Mass spectra of some classes of compounds: rules and examples 33. aliphaEc fluorides •  fluorine is monoisotopic (F ­19) •  polyfluorocarbons – base peak: m/z 69 (CF3+) •  loss of H atom gives a more stable ca$on than the loss of R• CHM3122 Interpreta$on of mass spectra 51 Mass spectra of some classes of compounds: rules and examples 34. hetero ­aromaEc compounds •  prominent molecular ion peak •  cleavage of β bonds is very common CHM3122 Interpreta$on of mass spectra 52 Summary Ionic Fragments Lost Fragments fragment m/z fragment m/z CnH2n+1 14n+1: 15, 29, 43, 57, 71… H2O 18 CnH2n 14, 28, 42, 56, 70 … CO 28 CnH2n ­1 13, 27, 41, 55, 69 …  ­CH3 15 C6H5+ 77  ­CH2 ­ 14 C7H7+ 91 CHO 29 31  ­OH 17 105 CO2H 45 NH3 17 NO2 46 NO 30 HS 33 +CH 2OH PhCO+ CHM3122 Interpreta$on of mass spectra 53 General Strategy 1.  Look for M+ molecular mass 2.  Analyse the isotopic peak presence of Br and/or Cl 3.  Nitrogen Rule # of N atoms 4.  Consult Appendix A Molecular Formula 5.  Calculate DHIndex unsatura$on 6.  Analyze fragmenta$on pagerns and consult Appendices B & C molecular structure 7.  IR/NMR confirm/amend your structure CHM3122 Interpreta$on of mass spectra 54...
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This note was uploaded on 11/10/2012 for the course SCIENCE 1, 2, 3 taught by Professor All during the Spring '12 term at University of Ottawa.

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