Identify the following compounds from their IR and proton NMR spectra.
(a) C4H6O: liberates a gas when treated with C2H5MgBr
(b) C5H6O
IR: 3300, 2102, 1634 cm-1
NMR: δ3.10 (1H, d, J = 2Hz); δ3.79 (3H, s); δ4.52 (1H, doublet of doublets,
J = 6 Hz and 2 Hz); δ6.38 (1H, d, J = 6 Hz)