Which of the two: O2NCH2CH2O– or CH3CH2O– is expected to be more stable and why?
NO2 group is an electron-withdrawing group. Hence, it shows –I effect. By withdrawing the electrons toward it, the NO2 group decreases the negative charge on the compound, thereby stabilising it. On the other hand, ethyl group is an electron-releasing group. Hence, the ethyl group shows +I effect. This increases the negative charge on the compound, thereby destabilising it. Hence, O2NCH2CH2O– is expected to be more stable than CH3CH2O–.
O2N——<——- CH2——<——- CH2 —<——- O– is more stable than CH3——<——-CH2——<——-O- because NO2 group has -I-effect and hence it tends to disperse the -ve charge on the O-atom. In contrast, CH3CH2 has +I-effect. It, therefore, tends to intensify the -ve charge and hence destabilizes it.