Metazachlor-d6 (BAS 479H-d6) is a deuterium labeled Metazachlor (HY-136373). Metazachlor (BAS 479H) is a herbicide belonging to the chloroacetamides class. Metazachlor can inhibit the synthesis of very long chain fatty acids during the germination and emergence of weed seeds, thereby interfering with cell division and tissue differentiation, and thus hindering the normal growth and development of weeds[1].