The analysis of substituted cathinones. Part 2: An investigation into the phenylacetone based isomers of 4-methylmethcathinone and N-ethylcathinone

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Abstract

During the analysis of “seized samples”, suspected of containing 4-methylmethcathinone (mephedrone) and N-ethylcathinone (ethcathinone) additional compounds were observed in the GCMS chromatogram. These compounds were suspected to be the corresponding phenylacetone isomers of mephedrone and ethcathinone respectively. These isomers are referred to as iso-mephedrone and iso-ethcathinone, respectively. The identity of these compounds was verified by synthesising the isomers from known starting materials and comparing them with the compounds found in the seized samples. Analytical data, GCMS, NMR and IR on these compounds are provided. Possible explanations for the presence of these compounds in the seized samples are explored. Contaminated starting material is one suggestion. Rearrangement of the propiophenone based product to the phenylacetone based product is also suggested. The reaction of the α-bromopropiophenone with a primary amine can also lead to the phenylacetone based product. The presence of these isomeric compounds in seized samples could be used to compare different samples and attempt to establish a common origin.

Introduction

The most commonly available cathinone sold on the recreational market in the period up to 2010 appears to be 4-methylmethcathinone (4-MMC, mephedrone) [1]. These products are usually encountered as highly pure, white or brown powders. Cathinone and methcathinone are listed in Schedule I of the United Nations 1971 Convention on Psychotropic Substances. N-ethylcathinone (ethcathinone) is also encountered as a substance of abuse in Ireland, however it is not presently listed as a controlled substance in Ireland.

The pharmacology of substituted cathinones has been studied [2]. The synthesis of these cathinones is relatively easy and the starting materials are readily available. Internet sites are used for the purchase of both the starting materials and the final products [3].

Analytical details on mephedrone and ethcathinone are available [4], [5], [6]. We recently reported on the separation of 2-, 3- and 4-MMC and gave analytical details on them [7]. During the analysis of a seized drug sample containing 4-MMC an extra compound was observed in the GCMS chromatogram and the presence of this compound together with the simultaneous detection of a similar compound in a seized sample of ethcathinone prompted us to examine in more detail the nature of these compounds.

Section snippets

Reagents and standards

Potassium bromide (IR grade) was obtained from Merck (Darmstadt, Germany). Methanol and acetonitrile were obtained from (Labscan, Poland). 4-Methylpropiophenone, propiophenone, methylamine, ethylamine, 2 M methylamine in THF, 2 M ethylamine in THF, bromine, dichloromethane and magnesium sulphate were obtained from Sigma–Aldrich (Ireland). 4-Methylphenylacetone was obtained from Alfa Aesar (UK). Phenylacetone was prepared by the oxidation of 1-phenyl-2-propanol (Sigma–Aldrich) with pyridinium

Results and discussion

The GCMS chromatogram for the seized sample of mephedrone is shown in Fig. 3. It can be seen that a compound is evident at approximately 6.4 min in addition to the mephedrone peak at approximately 8.2 min. The sample also contains benzocaine with a retention time of approximately 10.0 min. The GCMS chromatogram for the seized sample of ethcathinone is shown in Fig. 4. It can be seen that a compound is evident at approximately 5.4 min, together with the ethcathinone peak at approximately 6.5 min. The

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