The correct stability order of the following resonance structures of $$CH_3 - CH = CH - CHO$$ i

Solution

According to rules of making resonance structures, the most stable resonance structure is one which will have no charge, next would be the structure in which electronegative atom gets a negative charge i.e. Oxygen must have negative charge. The least stable resonating structure would be the structure that has a positive charge on oxygen opposite to its tendency. Hence, III>II>I