A quantitative investigation of the acid catalysed conversion of cannabidiol to tetrahydrocannabinol

Over the counter cannabidiol (CBD) oils can be used in acid catalysed reactions that convert the CBD present in the oil to THC. Online forums exist to lead people through the process to manufacture 9 – tetrahydrocannabinol (THC) from CBD oils. The legal landscape for cannabis-based products and their control varies widely across the world with cannabis-based products being legal in the US and some parts of Europe but there are no quality control guidelines for CBD oils which has led to many problems like mislabelling of products.

To test the ease by which CBD oil could be converted to THC, quantification of the acid catalysed conversion of CBD to THC was undertaken following a detailed review of the methods available. Three over the counter CBD oils with varying CBD concentrations were selected. These oils were screened by thin layer chromatography (TLC) for possible THC contamination. Then the oils were catalysed by a mixture of sulphuric acid and glacial acetic acid. The reaction mixture was then neutralised with sodium bicarbonate and extracted with petroleum ether. The petroleum ether layer was then analysed by TLC and gas-chromatography – mass spectrometry (GC-MS) to screen and confirm the content of the reaction mixtures respectively. All reaction mixtures were compared with CBD and THC standards as well as negative controls of each acid and solvent used.

The CBD oils catalysed produced different mixtures with THC present in every mixture and unknown peaks which can be tentatively identified using mass spectrum comparison on the NIST database. Screening the CBD oils for possible THC contamination suggests misleading product labelling was not found in products examined. Calculating THC yield from the conversion method resulted in a range of 0.007-0.015%. Finally, THC yield comparisons from the selected oils using the same conversion method produced minor percentage yield increases.