Ethinylestradiol Synonyms: NOVESTROL; NEO-ESTRONE; ETHYNYLESTRADIOL CAS NO: 57-63-6 Molecular Weight: 296.41 Molecular Formula: C20H24O2 Appearance: Off-White to Light-Yellow Crystalline Powder Usage: A metabolite of 17alpha-Ethynylestradiol A synthetic steroid with high oral estrogenic potency Standard: USP28