Ether : mass spectrum

The structures of long-chain bases can best be determined by mass spectrometry (Karlsson, 1970b). The dinitrophenylamines with their free hydroxyl groups methylated give characteristic fragmentation patterns for determination of their molecular weights and the primary structure of the base. Double-bond positions can be found if they are first hydroxylated and derivatized to TMS (tri-methylsilyl) ethers. Mass spectra can also be obtained (after GLC) of the A -acetyl, O-TMS ether derivatives of the base (Polito et aL, 1969). trans-Douhlc bonds can be identified by infrared absorption spectroscopy. 

Mass Spectrometry Ethers like alcohols lose an alkyl radical from their molecular ion to give an oxygen stabilized cation Thus m/z 73 and m/z 87 are both more abun dant than the molecular ion m the mass spectrum of sec butyl ethyl ether... 

There is another oxygen-stabilized cation of mIz 87 capable of being formed by fragmentation of the molecular ion in the mass spectrum of sec-butyl ethyl ether. Suggest a reasonable structure for this ion. 

Largest peak in the mass spectrum of propylene glycol ethers CH3OCH2CH2— (diethylene glycol dimethyl ether)... 

Figure 8 GC-MS detection of 2,4,4 -trichloro-2 -hydroxydiphenyl ether in the isooctane extract from a food container, from its mass spectrum.

Example The El mass spectra of 1-hexanol, Mj = 102, and 1-hexene, Mr = 84, show close similarity because the molecular ion peak is absent in the mass spectrum of hexanol (Fig. 6.40). However, a more careful examination of the hexanol spectrum reveals peaks at m/z 18, 19, 31, and 45 that are absent in the hexene spectrum. These are due to H20, HsO and to oxonium ions (H2C=OH and H3CCH=0H in this case) which are reliable indicators of aliphatic alcohols and ethers (Table 6.8). 

In 1987, Eurukawa et al. reported the isolation of oxydimurrayafoline (195) from the root bark of M. euchrestifolia. This alkaloid represented the first example of a dimeric carbazole alkaloid with an ether linkage (69). The UV spectrum (/Imax 242, 253, 294, 324, and 337nm) and the base peak at m/z 211 in the mass spectrum of oxydimurrayafoline (195) indicated a symmetrical dimeric carbazole with two murrayafoline A units. The H-NMR spectrum resembled that of murrayafoline A (7), except for the presence of a singlet at 8 4.76 instead of the singlet for the aromatic methyl group in murrayafoline A at 5 2.42. The singlet at 8 4.76 suggested a benzylic oxymethylene moiety. The spectral data, supported by NOE experiments, led to structure 195 for oxydimurrayafoline (Scheme 2.46). 

The fragmentation pathways responsible for the mass spectrum of oxepane have been studied using specifically deuterated oxepane and are comparable to those found in a non-branched acyclic ether (Scheme 1) (68OMS(l)403). 

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