Ionic species are stabilised by the dispersal of charge. Which of the following carboxylate ion is the most stable ?

Ionic species are stabilised by the dispersal of charge. Which of the

1.	Ionic species are stabilised by the dispersal of charge. Which of the following carboxylate ion is the most stable ?
Answer» `CH_(3)-overset(O)overset(\|\|)(C)-O^(-)` `Cl-CH_(2)-overset(O)overset(\|\|)(C)-O^(-)` `F-CH_(2)-overset(O)overset(\|\|)(C)-O^(-)` SOLUTION : In option (a), -ve charge on the carboxylate ion is intensified by R-effect of the `CH_(3)` group but in options (b), (c) and (d), it is dispersed by -I effect of the HALOGEN. Therefore, carboxylate ion (a) is the least stable. The stability of the other carboxylate IONS, however, depends upon the number of halogens atoms and their electronegativity. SINCE F has the highest electronegativity and option (d) has two such F atoms, therefore, DISPERSAL of -ve charge is maximum in option (d).