XLR11, a synthetic cannabinoid (CB) featuring a tetramethylcyclopropyl group, exhibits enhanced affinity for the CB2 receptor, common among synthetic CBs for its receptor affinity. XLR11 degradant, a frequent impurity identified in GC-MS analysis of XLR11-containing samples, originates from the thermal decomposition of XLR11, leading to an opened ring structure. This change results in a distinct fragment ion in mass spectrometry, being 15 amu heavier than XLR11's base peak. Such a signature is indicative of a McLafferty rearrangement in the degradant, a reaction not observed in the parent compound.