Question

what are carboxylate anions​

Answer 1

A carboxylate is the conjugate base of a carboxylic acid. Carboxylate salts have the general formula Mₙ, where M is a metal and n is 1, 2, ...; carboxylate esters have the general formula RCOOR′. R and R′ are organic groups; R′ ≠ H. A carboxylate ion is the conjugate base of a carboxylic acid, RCOO−



Carboxylic acids belong to a class of organic compounds in which a carbon (C) atom is bonded to an oxygen (O) atom by a double bond and to a hydroxyl group (−OH) by a single bond. A fourth bond links the carbon atom to a hydrocarbon group (R). The carboxyl (COOH) group is named after the carbonyl group (C=O) and hydroxyl group.



Diagram of a carboxylic molecule

In general, carboxylic acids undergo a nucleophilic substitution reaction where the nucleophile (-OH) is substituted by another nucleophile (Nu). The carbonyl group (C=O) gets polarized (i.e. there is a charge separation), since oxygen is more electronegative than carbon and pulls the electron density towards itself. As a result, the carbon atom develops a partial positive charge (δ+) and the oxygen atom develops a partial negative charge (δ-). In some cases, in the vicinity of a strong electrophile, the partially negatively charged carbonyl oxygen (δ-) can act as a nucleophile and attack the electrophile (as you will notice in the example of acid chloride synthesis, discussed later in this tutorial).

Compounds in which the −OH group of the carboxylic acid is replaced by other functional groups are called carboxylic acid derivatives, the most important of which are acyl halides, acid anhydrides, esters, and amides.

Overview of the reactions that we would be discussing in this tutorial



Diagram overview of carboxylic molecule reactions

Let’s list down some common properties for the above shown carboxylic acid derivatives

Each derivative contains a common group, termed as an acyl group (R-C=O), which is attached to a heteroatomThey can all be synthesized from the “parent” carboxylic acidThey are all formed through a nucleophilic substitution reactionOn hydrolysis (i.e. reaction with H_{2}2​start subscript, 2, end subscriptO), they all convert back to their parent carboxylic acid

Now let’s discuss each carboxylic acid derivative individually, and outline the reaction mechanism by which they are formed starting from the parent carboxylic acid

Answer 2

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A carboxylate is the conjugate base of a carboxylic acid. Carboxylate salts are salts that have the general formula Mₙ, where M is a metal and n is 1, 2, ...; carboxylate esters have the general formula RCOOR′. R and R′ are organic groups; R′ ≠ H. A carboxylate ion is the conjugate base of a carboxylic acid, RCOO