Phenylacetone forensic results has tell a chemical story that revolves around the chemical precursor known as phenyl-2-propanone (P2P), and since approximately 2009, the MPP has been tracking a methamphetamine clandestine P2P laboratory process that uses a foul-smelling crystalline material known as phenylacetic acid (PAA). This precursor is difficult to buy clandestinely; therefore, an ester of PAA, usually ethyl phenylacetate (EtPA), a perfume-like smelling oil sold in 200 L containers, is purchased.
This oil is very easily transformed into PAA using acid and base chemistry for the eventual P2P production. The two main recipes to convert PAA with modest yields into P2P are the Dakin-West reaction that uses acetic anhydride and sodium acetate as essential chemicals and the lead acetate reaction. The former reaction is heated for several hours producing a dark brown solution, which is then later distilled to obtain the P2P product. The latter reaction proceeds via a destructive distillation process using PAA and lead acetate, which are easily handled solid materials.
The resulting P2P oil produced from both of these reactions is converted to methamphetamine using either an amalgam or Leuckart reductive amination process. Impurities related to these processes have been well studied and are now routinely monitored in high purity methamphetamine samples. The key impurities from these processes are known as the B-compound (α-benzyl-N-methylphenethylamine) and the P-compound (trans-N-methyl-4-methyl-5-phenyl-4-penten-2-amine) and are used to track the PAA-based methamphetamine results.
It appears that the perfume oil (EtPA), and other related ester and amide materials became less available, because an alternative P2P production recipe started to emerge onto the forensic scene in 2014. At that time, a new impurity pattern was identified in the gas chromatography-mass spectrometry (GC-MS) analyses results for a significant portion of the seized samples. This led to uncertainty for the MPP, with a spike in unknown synthetic route assignments, and a sharp decrease (84%) in samples assigned to a P2P-based recipe in the first quarter of 2015 (Fig. 2). This new and unknown profile was quickly solved and P2P-based assignments went back to status quo (above 90%) in recent reporting periods, from 2016 to 2018. It should be noted that another forensic profiling team located in Australia has also observed this new profiling pattern in seized methamphetamine samples.
The old clandestine method responsible for the newly observed profiling pattern is referred to by the MPP as the nitrostyrene (NTS) method (it could also be called the nitropropene method). It uses benzaldehyde and nitroethane as the two key precursor chemicals in the process (Fig. 3). A Knoevenagel reaction resulting in NTS has long been known to produce a translucent, yellow solid (possibly orange if not filtered and dried well) as an easily managed intermediate in the first step of the method [19]. This solid is then converted to P2P in a harsh reaction using iron powder and hydrochloric acid [19], which leaves behind black solid iron sludge as waste. The P2P oil is then converted to methamphetamine using the same reductive amination chemistry as mentioned earlier for PAA-based methamphetamine.
Herein, we report forensic evidence that supports the recent P2P recipe change to be from the nitrostyrene method and will show the impact of this method on methamphetamine samples seized in the U.S.A. from 2015 to 2018. Apaan Powder CAS 4468-48-8 Systematic Conversion
Highlights
- •N-butylamphetamine and N-cyclohexylamphetamine are useful target impurities for tracking P2P- (Phenylacetone) based methamphetamine.
- •Spectral data for the two target compounds is provided in this report.
- •Profiling of laboratory prepared methamphetamine proved that the target impurities were related to the nitrostyrene method.
- •Methamphetamine profiling data shows that nitrostyrene related profiles have recently been dominant in the United States.
Abstract
N-butylamphetamine and N-cyclohexylamphetamine have been found to be useful target compounds for tracking P2P-based methamphetamine produced using nitrostyrene chemistry. Since 2015, these two process impurities have been detected at low levels in many seized methamphetamine samples and forensic information regarding these target compounds is provided in this report. Several laboratory experiments were performed using a variety of nitrostyrene related conditions to synthesize P2P. Methamphetamine was then produced using standard reductive amination conditions to prove that the presented target impurities were detected and therefore related to nitrostyrene chemistry. Methamphetamine profiling data is then presented to show that nitrostyrene related profiles have been dominant in the United States for the last 3 years.
Graphical abstract
Solvents, chemicals, and materials
All chemicals and solvents used were reagent grade or better. Petroleum ether and dichloromethane were obtained from VWR Corp. (West Chester, PA).
Reagents utilized for the nitrostyrene synthesis to P2P included nitroethane, benzaldehyde, iron powder, and iron (III) chloride (all from Sigma-Aldrich Chemical Co., St. Louis, MO), and hydrochloric acid (J.T. Baker, 36%) from Avantor Performance Materials Inc. (Center Valley, PA). Bmk oil
Reagents utilized for the mercury amalgam syntheses
Results and discussion
In the first step of the NTS method, either butylamine or cyclohexylamine are added in catalytic amounts to facilitate the Knoevenagel reaction process. These amines react nicely with benzaldehye to produce their corresponding imines, which then undergo carbon–carbon bond formation with the enolate of nitroethane. Elimination of the catalytic amines back into the reaction mixture results in nitrostyrene formation. These catalysts are therefore present as impurities in the reductive hydrolysis
Conclusions
The forensic identification and tracking of two new forensic NTS marker compounds 1 and 2 present at low levels in highly refined seized methamphetamine samples was discussed. These compounds were independently identified, synthesized, structurally elucidated, and then used as standards to support forensic analysis. A series of laboratory-generated samples using a variety of nitrostyrene and other related recipe choices were prepared and their profiling results compared well with actual seized
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