This work examined the synthesis and organic impurity profile of methylone prepared from catechol. The primary aim of this work was to determine whether the synthetic pathway used to prepare 3,4-methylenedioxypropiophenone could be ascertained through analysis of the synthesized methylone. The secondary aim was the structural elucidation and origin determination of the organic impurities detected in methylone and the intermediate compounds. The organic impurities present in the reaction products were identified using GC-MS and NMR spectroscopy. Six organic impurities were detected in 1,3-benzodioxole and identified as the 1,3-benzodioxole dimer, 1,3-benzodioxole trimer, [1,3] dioxolo[4,5-b]oxanthrene, 4,4'-, 4,5'-, and 5,5'-methylenebis-1,3-benzodioxole. Six organic impurities were detected in 3,4-methylenedioxypropiophenone and identified as (2-hydroxyphenyl) propanoate, [2-(chloromethoxy) phenyl] propanoate, (2-propanoyloxyphenyl)propanoate, 5-[1-(1,3-benzodioxol-5-yl)prop-1-enyl]-1,3-benzodioxole, (5E)- and (5Z)-7-(1,3-benzodioxol-5-yl)-5-ethylidene-6-methyl-cyclopenta[f][1,3]benzodioxole). Exploratory synthetic experiments were also conducted to unambiguously identify the organic impurities detected in 3,4-methylenedioxypropiophenone. Two organic impurities were detected in 5-bromo-3,4-methylenedioxypropiophenone and identified as [2-(chloromethoxy)phenyl] propanoate and 3,4-methylenedioxypropiophenone. Five organic impurities were detected in methylone and identified as 3,4-methylenedioxypropiophenone, 1-(1,3-benzodioxol-5-yl)-N-methyl-propan-1-imine, 1-(1,3-benzodioxol-5-yl)-2-methylimino-propan-1-one, 1-(1,3-benzodioxol-5-yl)-N1,N2-dimethyl-propane-1,2-diimine and butylated hydroxytoluene. The origin of these organic impurities was also ascertained, providing valuable insight into the chemical profiles of methylone and the intermediate compounds. However, neither the catechol precursor nor the 1,3-benzodioxole intermediate could be identified based on the organic impurities detected in the synthesized methylone using standard techniques. This demonstrated that the organic impurity profiling of methylone had limitations in the determination of precursor chemical and synthetic pathways used. Copyright © 2017 John Wiley & Sons, Ltd.