64
3 Combination Tables
Assignment
Range
Comments
Molecular ion
Aliphatic: weak, tendency to protonate
Aromatic: strong
Fragments
Aliphatic:
m/z 31, 45, 59, …
[M-33] +
Base peak of aliphatic ethers generally due to
fragmentation of the bond next to the ether
bond:
or due to heterolytic cleavage of the C–O
bond (especially for polyethers):
R 1 O R 2
+ - R 1 –O
.
R 2
+
.
Alkyl aryl ethers
Diaryl ethers
Preferential loss of the alkyl chain
Preferential loss of CO (Δm 28) from M +·
and/or [M-H] + as well as:
ar 1 O
ar 2
Rearrangements
Aliphatic:
[M-18] +·
[M-46] +·
Elimination of water or alcohol
Aromatic
Ethyl and higher alkyl ethers: alkene elimination to the phenol:
O
H
R
+
- R C H =C H 2
OH
+ .
.
Aliphatic
Aromatic
No absorption above 200 nm
Shift to higher wavelength and increase in
intensity due to the ether group
R 1 C O R 2
+
- R 1
.
C O R 2
+
.
MS
UV