- Carboxylate
A carboxylate anion is an
ion withnegative charge that contains the group -COO−. It is theconjugate base of acarboxylic acid .Carboxylic acids dissociate into a carboxylate ion and a positively-charged hydrogen ion (proton) much more readily than alcohols dissociate (into an
alkoxide ion and a proton), because the carboxylate ion is more stable: the negative charge that is left behind when a proton leaves the carboxylate group is 'shared' between the two electronegative oxygen atoms in a resonance structure. Thisdelocalization of the electron cloud means that neither of the oxygen atoms is so strongly negatively charged; the positively-charged proton is therefore less readily attracted back to the carboxylate group once it has left. On the other hand, an alkoxide ion, once formed, would have a strong negative charge on the oxygen atom, which would make it difficult for the proton to escape. Thus, the carboxylate ion is more stable - this is also why carboxylic acids have a lowerpH than alcohols: the higher the number of protons that escape into solution, the lower the pH. [cite book | author= Fox, Marye Anne; Whitesell, James K. | year = 1997 | title = Organic Chemistry | edition = 2| publisher = Jones and Bartlett Publishers | location = Sudbury, Massachusetts| id = ISBN 0-7637-0178-5 ]Examples
*
formate ion, HCOO−
*acetate ion, CH3COO−Discussion
References
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