(a) The 1H NMR spectrum of a ketone with the molecular formula C6Hl2O has ( = 1.2 and 2.1 ppm (ratio 3:1). Propose a structure for this molecule.
(b) Each of two isomeric molecules related to the ketone in (a) has the molecular formula C6H12O2. Their 1H NMR spectra are described as follows: isomer 1, ( = 1.5 and 2.0 ppm (ratio 3:1); isomer 2, ( = 1.2 and 3.6 ppm (ratio 3:1). All signals in these spectra are singlets. Propose structures for these compounds. To what compound class do they belong?