Strigol is an important plant hormone that is released by crops such as rice and sugarcane. Unfortunately for these plants, strigol also activates the germination of any nearby witchweed seeds, resulting in the destruction of the crops by the parasitic weed. Strigol has nineteen carbon atoms. Determine the HDI of strigol, as well as its molecular formula. Strigol has four rings and five double bonds, for a total hydrogen deficiency index of 10 . If saturated, a compound with 19 carbon atoms would have 40 hydrogen atoms, but an HDI of 10 means that 20 hydrogen atoms are missing. So there must be 20 hydrogen atoms in the formula. Inspection of the structure also reveals 6 oxygen atoms, so the molecular formula of strigol must be C 19 H 20 O 6 .