2-Methyl-4-isothiazolin-3-one Hydrochloride

2-Methyl-4-isothiazolin-3-one Hydrochloride is a chlorinated heterocyclic compound featuring a five-membered isothiazolinone ring substituted with a methyl group at the 2-position and a hydrochloride salt. The core structure comprises a sulfur atom adjacent to a nitrogen atom, forming a thiazole moiety, with a ketone at position 3. This compound arises as a synthetic byproduct during the preparation of isothiazolinone-based biocides or pharmaceutical intermediates. Its hydrochloride salt enhances solubility in polar solvents, facilitating use in HPLC reference standards for quantifying process-related impurities in parent drug formulations.