Peak genrally decreases as the molecular

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Unformatted text preview: erty rearrangement – H migra$on CHM3122 Interpreta$on of mass spectra 19 Mass spectra of some classes of compounds: rules and examples 1. Saturated hydrocarbons •  molecular ion peak always present •  observe losses of m/z = 14 (CH2) •  14n + 1 (CnH2n+1 fragments) = 29, 43, 57… •  linear: do not see a M ­15 peak (M ­CH3) CHM3122 Interpreta$on of mass spectra 20 Mass spectra of some classes of compounds: rules and examples cyclic compounds : loss of CnH2n ­1, CnH2n ­2 CHM3122 Interpreta$on of mass spectra 21 Mass spectra of some classes of compounds: rules and examples 2. alkenes •  molecular ion peak generally visible •  observe losses of m/z = 14 (CH2) •  peaks at CnH2n ­1, CnH2n, CnH2n+1 CHM3122 Interpreta$on of mass spectra 22 Mass spectra of some classes of compounds: rules and examples CHM3122 Interpreta$on of mass spectra 23 Mass spectra of some classes of compounds: rules and examples 3. aromaEc hydrocarbons •  molecular ion peak is generally visible CHM3122 Interpreta$on of mass spectra 24 Mass spectra of some classes of compounds: rules and examples 4. alcohols •  the molecular ion peak is usually weak to very weak (indetectable for ter$ary alcohols) •  common fragments: loss of water (M ­18) or alkyl groups •  cleavage of C ­C next to the O atom CHM3122 Interpreta$on of mass spectra 25 Mass spectra of some classes of compounds: rules and examples CHM3122 Interpreta$on of mass spectra 26 Mass spectra of some classes of compounds: rules and examples Benzylic alcohols: CHM3122 Interpreta$on of mass spectra 27 Mass spectra of some classes of compounds: rules and examples 5. phenols •  visible molecular ion peak •  observe m/z = 77 and some$mes the loss of CO ( ­28) and/or CHO (M ­29) CHM3122 Interpreta$on of mass spectra 28 Mass spectra of some classes of compounds: rules and examples 6. aliphaEc ethers and acetals •  weak molecular ion peak •  cleavage of C ­C bond next to the O atom •  cleavage of C ­O bond CHM3122 Interpreta$on of mass spectra 29 Mass spectra of some classes of compounds: rules and examples 7. aromaEc ethers • large molecular ion peak • primary cleavage at the β posi$on CHM3122 Interpreta$on of mass spectra 30 Mass spectra of some classes of compounds: rules and examples 8. aliphaEc ketones •  molecular ion peak is usually prominent •  major fragmenta$on: cleavage of C ­C bonds next to the carbonyl •  fragments of m/z = 43, 57, 71… (alkyl groups) CHM3122 Interpreta$on of mass spectra 31 Mass spectra of some...
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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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