§ TETRAHYDROCANNABINOL / THC / THCD / C₂₁H₃₀O₂ / CAS 1972-08-3
Tetrahydrocannabinol
Tetrahydrocannabinol (THC; classification code THCD) is the principal psychoactive cannabinoid of Cannabis sativa, with molecular formula C₂₁H₃₀O₂ and molar mass 314.47 g/mol. Tetrahydrocannabinol is the analyte referenced by federal hemp thresholds, THC laboratory potency reporting, and international THCD treaty classification.
Chemistry
The naturally occurring form is the (−)-trans-Δ9 enantiomer (CAS 1972-08-3). Positional isomers Δ8, Δ9, and Δ10 share the same molecular formula but differ in receptor affinity, metabolism, and regulatory treatment.
THCA and Decarboxylation
Tetrahydrocannabinolic acid (THCA) is the non-psychoactive carboxylated precursor. Heat removes CO₂ to yield Δ9-THC. Total THC is reported as Δ9-THC + (THCA × 0.877).
Endocannabinoid System
THC is a partial agonist at the CB1 receptor (CNS) and is also active at CB2 (peripheral and immune). Endogenous ligands include anandamide and 2-arachidonoylglycerol.
Metabolism
Hepatic CYP2C9 and CYP3A4 produce 11-hydroxy-THC, an active metabolite, which is further oxidized to 11-nor-9-carboxy-THC (THC-COOH), the inactive analyte detected in urine drug screening.
Impairment vs Detection
Acute impairment from inhaled cannabis lasts approximately 2–4 hours; oral cannabis 6–8 hours. Urine detection of THC-COOH can extend days to weeks. Detection is not equivalent to active impairment.
Laboratory Analysis
HPLC is the standard method for cannabinoid potency because it preserves THCA as a separate analyte. GC requires elevated injector temperatures that decarboxylate THCA. ISO/IEC 17025 accreditation governs laboratory competence and method validation.
Certificate of Analysis
A defensible COA identifies the issuing laboratory and accreditation, the sample chain of custody, the cannabinoid panel with limits of detection and quantitation, and the regulated contaminant panel against jurisdiction-specific action limits.
U.S. Federal Thresholds
The 2018 Agriculture Improvement Act defines hemp as Cannabis sativa with no more than 0.3% Δ9-THC by dry weight. Material above the threshold remains a Schedule I controlled substance under the Controlled Substances Act. FDA, USDA, and DEA exercise overlapping jurisdiction.
International Regulation
National policy varies. The EU permits industrial hemp up to 0.3% THC; Canada operates a federal adult-use program; the UK restricts cannabis as Class B with limited prescription access; Australia authorizes medical cannabis through the TGA.
UN Treaty Classification
The 1961 Single Convention on Narcotic Drugs and the 1971 Convention on Psychotropic Substances govern international control. The 2020 CND vote removed cannabis from Schedule IV of the 1961 Convention but left it in Schedule I.
Labeling and Workplace
Compliance labels disclose Total THC, serving size, batch identity, and laboratory reference, in child-resistant packaging. Workplace policy is most defensible when the analyte tested matches the question asked: urine THC-COOH evidences past exposure; oral fluid Δ9-THC evidences recent use.