Page 117 - Org 3 theoritical book 2024-25

Clinical Pharmacy PharmD - 2024/2025 Level 2 Pharmaceutical Organic Chemistry-3 (PC 305)

❖ Fragmentation occurs when energetically unstable molecular atoms dissociate as they
pass through the ionization chamber of a mass spectrometer.
❖ Some fragmentation patterns of various compounds will be discussed in the next tables:

[M ] peak
+
+
+
+
• Molecular ion peaks (M ) • Molecular ion peak (M ) is • Molecular ion peaks (M )
are present, possibly with strong due to the stable are present.
low intensity. structure.
Fragmentation Pattern
• The fragmentation pattern • The fragmentation is • Major fragmentation peaks
contains clusters of peaks 14 minor and limited to the result from cleavage of the
m/z units apart (which aromatic substituents only C-C (& C-H in aldehydes)

represent loss of (CH2)nCH3 in most cases. bonds adjacent to the
(where n= 0 up to …..). carbonyl (C=O).
• In aldehydes, –H (-1 m/z)
is a characteristic ion in
most MS spectra resulted
from C-H bond cleavage.
Example