rac-Mono-(4-methyloctanyl)-phthalate-D4 is the isotopically labeled analog of rac-Mono-(4-methyloctanyl)-phthalate. rac-Mono-(4-methyloctanyl)-phthalate, is similar to di-isonoyl phthalate esters (DINPs) which are used as a major plasticizer for poly(vinyl chloride) (PVC). This family of compounds (phthalate) are considered endocrine-disrupting chemicals based on biological studies.