MOLECULE

Isoquinoline

Isoquinoline, also known as 2-benzazine, belongs to the class of organic compounds known as isoquinolines and derivatives. Isoquinoline is a heterocyclic aromatic organic compound. It is a structural isomer of quinoline. Isoquinoline and quinoline are benzopyridines, which are composed of a benzene ring fused to a pyridine ring. Isoquinoline is a weak basic compound (based on its pKa). Being an analog of pyridine, isoquinoline is a weak base, with a pKb of 8.6. It protonates to form salts upon treatment with strong acids, such as HCl. It forms adducts with Lewis acids, such as BF3. Isoquinoline is a colorless hygroscopic liquid at room temperature with a penetrating, unpleasant odor. Impure samples can appear brownish, as is typical for nitrogen heterocycles. It crystallizes as platelets that poorly soluble in water but dissolve well in organic solvents such as ethanol, acetone, and diethyl ether. It is also soluble in diluted acids, due to the formation of the protonated salt derivative. 1-Benzylisoquinoline is the structural backbone in naturally occurring alkaloids including papaverine and morphine. The isoquinoline ring in these natural compounds derives from the aromatic amino acid tyrosine. Isoquinoline has also been detected in the volatile fraction of Cannabis sativa samples, obtained from police seizures (PMID: 26657499). Isoquinoline is also found in cannabis smoke and is volatilized during the combustion of cannabis (https://doi.org/10.1007/978-1-59259-947-9_2).