Mass Spec Fragmentation Patterns

alcohol fragmentation pattern

cleavage of C-C bond next to C-OH

loss of H₂O may also occur

aldehyde fragmentation pattern

cleavage of H off of carbonyl results in molecular ion -1 peaks

cleavage of C-OH results in molecular ion -29 peaks

alkane fragmentation pattern

contains clusters of peaks 14 mass units apart, representing the loss of CH₂

McLafferty rearrangement

gamma hydrogen attacks carbonyl

amide fragmentation pattern

can show in the base beak due to McLafferty rearrangement

amine fragmentation pattern

molecular ion peak will be odd number (if only one amine is present)

for aliphatic amines, cleavage at the alpha carbon often occurs

aromatic fragmentation pattern

ring structure peaks are strong

carboxylic acid fragmentation pattern

for short chain acids, peaks due to the loss of OH (molecular ion -17) and COOH (molecular ion -45) are prominent due to cleavage of bonds next to C=O

ester fragmentation pattern

bond cleavage next to carbonyl

ether fragmentation pattern

tend to occur at alpha carbon from oxygen

halide fragmentation pattern

halogens will cleave off to form recognizable peaks

be careful of multiple isotopes

ketone fragmentation pattern

Major fragmentation peaks result from cleavage of the C-C bonds adjacent to the carbonyl