Carboxylate ion
Acrylate ion
A carboxylate is a conjugate base of a carboxylic acid, RCOO−. It is an ion with negative charge.
Resonance stabilization of the carboxylate ion
Carboxylic acids easily dissociate into a carboxylate anion and a positively charged hydrogen ion (proton), much more readily than alcohols do (into an alkoxide ion and a proton), because the carboxylate ion is stabilized by resonance. The negative charge that is left after deprotonation of the carboxyl group is delocalized between the two electronegative oxygen atoms in a resonance structure.
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This delocalization of the electron cloud means that both of the oxygen atoms are less strongly negatively charged; the positive proton is therefore less strongly attracted back to the carboxylate group once it has left; the carboxylate ion is more stable . In contrast, 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. Carboxylic acids have a lower pH than alcohols: the higher the number of protons in solution, the lower the pH.[1]
Uses
Polycarboxylate ethers serve as the main component of superplasticizers, admixtures used in the construction industry.
Examples
References
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^ Fox, Marye Anne; Whitesell, James K. (1997). Organic Chemistry (2 ed.). Sudbury, Massachusetts: Jones and Bartlett Publishers.
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