Published:Journal of Chromatographic Science, ISSN 0021-9665 Volume 45, Number 8, September 2007, pp. 458-467

Gas Chromatography–Mass Spectrometry Analysis of Regioisomeric Ring Substituted Methoxy Methyl Phenylacetones

Tamer Awad, Jack DeRuiter, and C. Randall Clark
Department of Pharmacal Sciences, School of Pharmacy, Auburn University, Auburn, AL 36849

The methoxy methyl phenylacetones share an isobaric relationship (equivalent mass but different elemental composition) to the controlled precursor substance 3,4-methylenedioxyphenylacetone. The 10 methoxy methyl phenylacetones as well as the methylenedioxyphenylacetones show essentially equivalent mass spectra with major fragment ions at m/z 135 and 43. Those methoxy methyl phenylacetones with the methoxy group substituted ortho to the benzylic cation in the m/z 135 ion show a further fragmentation to lose formaldehyde (CH2O) and yield a significant ion at m/z 105. The loss of formaldehyde from the ortho methoxy benzyl cation was confirmed using commercially available regioisomeric 2-, 3-, and 4-methoxyphenylacetones. The 10 regioisomeric methoxy methyl phenylacetones were prepared from the appropriately substituted benzaldehydes. Complete gas chromatographic resolution of all ten regioisomeric ketones was obtained on a stationary phase containing modified b-cyclodextrin. Using the cyclodextrin containing phase, the ortho methoxy-substituted ketones (K1–K4) eluted before the meta-methoxy-substituted ketones (K5–K8) and the para-methoxy-substituted ketones (K9–K10) showed the greatest affinity for the stationary liquid phase and eluted last. Complete separation of the 10 ketones was not obtained on Rtx-1 and Rtx-200 columns.

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