Such as co alkenes water ammonia

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Unformatted text preview: classes of compounds: rules and examples 9. cyclic ketones CHM3122 Interpreta$on of mass spectra 32 Mass spectra of some classes of compounds: rules and examples 10. aromaEc ketones CHM3122 Interpreta$on of mass spectra 33 Mass spectra of some classes of compounds: rules and examples 11. aliphaEc aldehydes • molecular ion peak generally visible • cleavage of the α,β bond gives a major peak at m/z = 44, 58, or72, etc. : CHM3122 Interpreta$on of mass spectra 34 Mass spectra of some classes of compounds: rules and examples 12. aromaEc aldehydes • large molecular ion peak; intense peak at M ­1 (Ar ­CO+) • phenyl ion (m/z = 77) • loss of acetylene gives the C4H3+ ion (m/z = 51) 13. aliphaEc carboxylic acids • weak molecular ion peak • peak at m/z = 60 is a characteris$c peak, caused by a McLafferty rearrangement: CHM3122 Interpreta$on of mass spectra 35 Mass spectra of some classes of compounds: rules and examples 14. aromaEc carboxylic acids •  prominent molecular ion peak •  other peaks: loss of OH (M ­17), loss of CO2H (M ­45) •  loss of other neutral molecules: CHM3122 Interpreta$on of mass spectra 36 Mass spectra of some classes of compounds: rules and examples 15. aliphaEc esters •  weak molecular ion peak •  McLafferty rearrangements: CHM3122 Interpreta$on of mass spectra 37 Mass spectra of some classes of compounds: rules and examples 16. benzylic and phenylic esters • loss of a ketene gives the base peak: benzyl acetate: m/z = 43 (CH3C=O)+ m/z = 91 (C7H7)+ CHM3122 Interpreta$on of mass spectra 38 Mass spectra of some classes of compounds: rules and examples 17. esters of aromaEc esters (ArCOOR) •  prominent molecular ion peak •  base peak caused by loss of RO• •  might observe peak of •COOR 18. lactones CHM3122 Interpreta$on of mass spectra 39 Mass spectra of some classes of compounds: rules and examples 19. aliphaEc amines •  odd molecular ion peak is weak •  cleavage of C ­C bond next to N atom •  loss of alkyl groups most common fragment CHM3122 Interpreta$on of mass spectra 40 Mass spectra of some classes of compounds: rules and examples 20. aromaEc amines (anilines) •  odd molecular ion peak is prominent •  aniline: loss of HCN → CN ­ gives peaks at m/z = 66 and 65 •  cleavage of C ­C bond next to N atom CHM3122 Interpreta$on of mass spectra 41 Mass spectra of some classes of compounds: rules and examples 21. aliphaEc amides •  base peak at m/z = 59 (H2NC(=OH+)CH2•) •  primary amides: m/z = 44 (O=C=+NH2)...
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