Carboxylate: Difference between revisions

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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; hence, 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 thus have a lower [[pKa]] values than alcohols. For example, the pKa value of ethanol is 16 while acetic acid has a pKa of 4.9. Hence acetic acid is a much stronger acid than ethanol. the higher the number of protons in solution, the lower the pH.<ref>{{cite book | last1= Fox|first1= Marye Anne|last2= Whitesell|first2= James K. | year = 1997 | title = Organic Chemistry | edition = 2nd| publisher = Jones and Bartlett Publishers | location = Sudbury, MA| isbn = 0-7637-0178-5 }}</ref>
== Reactions ==
=== Nucleophilic Substitution ===
Carboxylate ions are good [[nucleophile|nucleophiles]]. They react with [[alkyl halides]] to form [[ester]]. The following reaction shows the reaction mechanism.
[[File:Ester-from-carboxylate-and-alkyl-halide-2D-skeletal.png|thumb|The [[SN2 reaction|S<sub>N</sub>2 reaction]] between [[sodium acetate]] and [[bromoethane]]. The products are [[ethyl acetate]] and [[sodium bromide]]. |alt=|none|287x287px]]