Two constitutional isomers having molecular formula c4h6o are both symmetrical in structure. in their infrared spectra, neither isomer when in dilute solution has absorption in the 3600 cm−1 region. isomer a has absorption bands at approximately 3080, 1620, and 700 cm−1 . isomer b has bands in the 2900 cm−1 region and at 1780 cm−1 . propose a structure for a and two possible structures for b.