17.1 Mass spectrometry

mass spectrometry

use the molecular ion peak from a mass spectrum to determine the molecular mass

use of fragment ions to identify sections of a molecule

molecular ion M⁺

positive ion formed when a molecule loses an electron

M+1

due to natural abundance of carbon-13

the height of this peak is relative to the peak for the molecular ion, depends on the number of carbon atoms in the molecule

fragmentation

some molecular ions in the mass spectrometer break down into fragments

fragment ions

other peaks in a mass spectrum

what does the simplest fragmentation form

a positively charged fragment ion and a radical

CH₃⁺

15

C₂H₅⁺

29

C₃H₇⁺

43

C₄H₉⁺

57

C₅H₁₁⁺

71

C₆H₁₃⁺

85

stability trend with peak

the more stable the cation, the higher the peak

why do multiple peaks occur in the molecular ion eigon

different halogen isotopes

why will CO not produce a peak of its own

molecule

uncharged

CO drop

28