carboxylate group is an organic group made up of a carbon atom that attaches to a two-way oxygen atom and binds separately to a hydroxyl group. Another way to view it is as a carbonyl group (C = O), which has a hydroxyl group (O-H) attached to the carbon atom.
Carboxyl groups are common in many biological molecules, including amino acids and fatty acids. Molecules containing carboxylic groups are called carboxylic acids and are partially separated into H and COO−. The carboxylate group is sometimes referred to as the carboxyl group, the carboxyl functional group, or the radical carboxyl group. It is usually written as -C (= O) OH or -COOH.
The carboxylate group is ionized by releasing hydrogen atom from the -OH group. H +, a free proton, is released. Therefore, Carboxyl groups form good acids. When leaving hydrogen, the oxygen atom has a negative charge that it shares with the second oxygen atom in the group, causing the carboxyl to remain stable even during oxidation.
Carboxyl groups are often ionized, releasing H from the hydroxyl group as a free proton (H +), and the remaining O has a negative charge. This throws the oxygen atom back and forth between the two atoms, making the ionized state relatively stable.
Common reactions convert carboxylic acids to esters, amides, carboxylate salts, acid chlorides, and alcohols. Carboxylic acids react with the base to form carboxylate salts, in which the hydrogen of the hydroxyl group (-OH) is replaced by a metal cation.
Carboxylic acids also react with alcohol to induce esters. This process is widely used, for example in the production of polyester. Similarly, carboxylic acids are converted to amide, but this conversion does not usually occur with a direct reaction of carboxylic acid and amine. The hydroxyl group in carboxylic acids may also be replaced with a chlorine atom using thalionyl chloride to form acid chlorides.
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