A Note about some Impurities in Commercially Available Piperonylmethylketone

Introduction

Diketone compounds are known impurities present in the ketones that are used as starting materials in the different syntheses of 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA)¹. No further studies have been reported in the literature on impurities present in piperonylmethylketone (PMK) (also known as 3,4-methylenedioxyphenyl-2-propanone, MDP2P), used in the illicit production of MDA. Some of these impurities, and their structures, have been determined in commercially available PMK.

Experimental

Analyses were done on a 1:40 dilution of PMK with chloroform. Gas chromatographic-mass spectral analyses were performed on 1 uL injections using a HP 5971A MSD interfaced with a HP 5890 GC. The MSD was operated in the EI mode. The samples were introduced into the GC via a split injector equipped with a 12.5 m x 0.2 mm id HP Ultra-1 fused silica capillary column with a 0.33 um film thickness. The column temperature was programmed from 100 to 280°C at a rate of 10°C per minute. The injection port was 275°C and the transfer line temperature was 280°C. He was used as the carrier gas with a flow rate of about 1 mL/minute.

Results and discussion

Table 1

Peak	Compound Name	MW.	Formula
A	Safrole	162	C₁₀H₁₀O₂
A	Isosafrole	162	C10H10O2
B	Piperonal	150	C8H6O3
C	4-Allyl-1,2-dimethoxybenzene	178	C11H14O2
D	Piperonylmethylketone (PMK, MDP2P - Main Component)	178	C10H10O3
E	3,4-Methylenedioxyphenyl- 2-propanone-(3-ol)	194	C10H10O4
F	3,4-Methylenedioxyphenyl- 1-propanone	178	C10H10O3
G	3,4-Methylenedioxyphenyl- 1-butanone	172 (sic)	C11H12O3
H	4-Isopropyl-1,6-dimethyl- 1,2,3,4-tetrahydronaphtalene	202	C15H22
I	3,4-Methylenedioxyphenyl- propionic acid-2-one	208	C10H8O5

The total ion chromatogram (TIC) of a solution of PMK in chloroform is shown in Fig 1 (not included). From the abundance values for the peaks in the TIC shown in Fig 1, the purity of the PMK was estimated to be greater than 95 percent. In the same way, the impurities were found to range from about 0.1 to 1.0 percent. The structure elucidation of the different compounds in the TIC was done by comparing the mass spectral data with different databases^1-3 and applying known fragmentation rules^4,5. In Table 1, the proposed structures of the impurities together with the mass spectral data are given. All the detected impurities except compounds C and H, have the methylenedioxy group, whereas the other structural differences of the impurities are in the substituents attached to the other side chain of the phenyl group. A trace quantity of safrole, as well as isosafrole, was found, giving rise to the assumption that at least the oxidation of safrole in formic acid by hydrogen peroxide was part of the process of manufacturing PMK. The presence of the oxidation products of PMK, the alcohol and the acid (compounds E and I in Table 1), also points to an oxidative process.