Carboxylic acid
In chemistry, carboxylic acids (also called organic acids or alkanoic acids) are acids characterized by the presence of a carboxyl group. They can be made by the complete oxidation of primary alcohols - this means the alcohol group is at the end of the molecule. In chemical formulas, these groups are typically represented as COOH.
| Table of contents |
|
2 Reactions 3 Electron distribution and resonance 4 Examples 5 Derivatives |
All carboxylic acids are weak acids, with only about 1% of RCOOH molecules dissociated into ions at room temperature in aqueous solution.
Carboxylic acids react with basess to form carboxylate salts, in which the hydrogen of the -OH group is replaced with a metal ion.
Thus, ethanoic/acetic acid reacts with sodium bicarbonate (baking soda) to form sodium ethanoate (sodium acetate), carbon dioxide, and water:
Carboxylic acids can be reduced by LiAlH4 to form primary alcohols:
The two electronegative oxygen atoms tend to pull the electron away from the hydrogen of the hydroxyl group, and the remaining proton can more easily leave.
The remaining negative charge is then distributed symmetrically among the two oxygen atoms, and the two carbon–oxygen bonds take on a partial double bond character (i.e., they are delocalised).
This is a result of the resonance structure created by the carbonyl component of the carboxylic acid, without which the OH group does not as easily lose its H+ (see alcohol).
The resulting ion is typically named with the suffix "-ate", so acetic acid, for example, becomes acetate ion.
Some carboxylic acids include:
Acidity
Reactions
Carboxyl groups also react with amine groups to form peptide bonds and with alcohols to form esters.
Electron distribution and resonance
Examples
Derivatives