Question

Which of the two: O₂NCH₂CH₂O^– or CH₃CH₂O^– is expected to be more stable and why?  

Answer 1

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^–.