|
G. Bhaskar,a S.
Prabhakar,a,* A. Venkat Narsaiah,b K.
Nagaiah,b G.S. Ramanjaneyulua and M.
Vairamania
aNational Center for Mass Spectrometry,
Indian Institute of Chemical Technology, Hyderabad 500 007, India. E-mail:
prabhakar@iict.res.in
bDivison of Organic Chemistry, Fine
Chemicals Laboratory, Indian Institute of Chemical Technology, Hyderabad 500
007, India |
| A series of isomeric
substituted diaryl ethers, i.e., 2- or 4-NO2,
5-F–C6H3–O–C6H4
(4-R), where R = H, COCH3, COOCH3, NO2, CHO,
OCH3 etc., which comprise ortho and para isomers with
respect to the position of the nitro group are studied under GC-EI-MS and CI-MS
conditions. The EI mass spectra of ortho and para isomers show
distinct fragment ions, where the [M–OH]+ and
[M–OH–O]+ ions specifically appeared in all spectra of the
ortho isomers (I), whereas the para isomers (II)
contain [M–O]+ and [M–NO]+ ions. The
[M–OH–CO]+ and [M–OH–NO]+ ions in
I, and [M–NO2]+ ion in II are the
other specific fragment ions observed but feasibility of these fragment ions
are found to depend on the nature of the substituent (R). The substitution
(–R) effect is also clearly reflected in the formation of fragment ions
due to s-cleavage process with or without hydrogen migration. Similar
differences in the formation of specific fragment ions are also observed in
ortho and para isomers of substituted aryl naphthyl ethers. The
methane/CI of isomeric compounds resulted in the same set of fragment ions, but
prominent differences are observed in the relative abundance of
[MH–NO]+, which is relatively higher in para isomers
compared with corresponding ortho isomer. |
|
Keywords: substituted diaryl
ethers, EI mass spectra, specific fragment ions, ortho effect, methane
chemical ionization |
