Unknown Y has a molecular formula of C3H6O2. It contains one functional group that absorbs infrared radiation in the 3200-3550 cm-1region (when studied as a pure liquid; i.e., "neat"), and it has no absorption in the 1620-1780 cm-1region. No carbon atom in the structure of Y has more than one oxygen atom bonded to it and Y can exist in two (and only two) stereoisomeric forms. What is the structure of one of these forms of Y?