View source for Carboxylic acid

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A '''carboxylic acid''' is an organic compound that contains at least one carboxyl group ('''-COOH''') or ('''-C(=O)OH'''). The general formula of a carboxylic acid is '''R–COOH''', with R being a substituent, usually organic.

==Types==
Carboxylic acids can be classified under several categories:
*Monocarboxylic acids: only have one -COOH group. Most are liquid at room temperature and have strong odor. Ex: [[formic acid]], [[acetic acid]];
*Dicarboxylic acids: have two -COOH groups. Solid and poorly volatile at standard conditions. Ex: [[oxalic acid]], [[succinic acid]];
*Polycarboxylic acids: can have more than three -COOH groups. Solid and non-volatile. Ex: [[citric acid]];
*Organic: The R substituent is an organic group. Ex: [[acetic acid]], [[benzoic acid]].
*Inorganic: The R substituent is an inorganic group (exception for formic acid, where R is [[hydrogen|H]] and is organic due to the C-H bond). Ex: [[carbonic acid]], [[trifluoroacetic acid]];
*Aminoacids: Organic carboxylic acids that also contain an amino (-NH<sub>2</sub>) group. Ex: [[glycine]];

Salts and esters of carboxylic acids are called carboxylates. The carboxylate anion R–COO<sup>−</sup> is usually named with the suffix ''-ate'' (ex: formic acid - form''ate'').

==General properties==
Monocarboxylic acids are liquid (except for aromatic), volatile and have a strong poignant smell. Polycarboxylic acids on the other hand are all solids and non-volatile. Carboxylic acids are polar compounds.

Carboxylic acids are Brønsted–Lowry acids because they are proton (H<sup>+</sup>) donors. Generally they are weak acids.

==Availability==
Concentrated [[formic acid]] is sold by various beekeeping stores, as is [[acetic acid|acetic]] and [[oxalic acid|oxalic acids]]. 

[[Citric acid]] can be purchased as lemon salt from most stores, while diluted acetic acid is available as vinegar.

[[Benzoic acid]] can be made by acidifying [[sodium benzoate]], which is sold as food preservative. [[Tartaric acid]] can be easily made from potassium tartrate, in the same way.

==Preparation==
Oxidation of primary alcohols, such as methanol or ethanol with [[potassium permanganate]] in the presence of sulfuric acid will give their respective carboxylic acids. [[Jones oxidation]] is another route.

: CH<sub>3</sub>OH + [O] → HCOOH + H<sub>2</sub>O
: CH<sub>3</sub>CH<sub>2</sub>OH + [O] → CH<sub>3</sub>COOH + H<sub>2</sub>O

Carbonation of a [[Grignard reagent|Grignard]] and organolithium reagents, followed by acidification:

: RLi + CO<sub>2</sub> → RCO<sub>2</sub>Li
: RCO<sub>2</sub>Li + HCl →  RCO<sub>2</sub>H + LiCl

Carboxylates are the side products from the [[haloform reaction]]. The following ketones/alcohols will give the following carboxylates:
*[[Ethanol]]/[[acetaldehyde]] - Formate
*[[Acetone]]/[[isopropanol]] - Acetate
*[[Methyl ethyl ketone]]/[[sec-Butanol]] - Propanoate
*[[Acetylacetone]] - Acetate
*[[Acetophenone]] - Benzoate

==Safety==
Concentrated carboxylic acids, such as formic or acetic acids are corrosive to skin and have a strong irritant smell. Wear proper protection when working with them.

Polycarboxylic acids are less corrosive and volatile, though conc. aqueous solutions are irritant.

==References==
<references/>
===Relevant Sciencemadness threads===
*[http://www.sciencemadness.org/talk/viewthread.php?tid=63525 Test for carboxylic acids]
*[http://www.sciencemadness.org/talk/viewthread.php?tid=8152 Carboxylic acid -> Alkan]
*[http://www.sciencemadness.org/talk/viewthread.php?tid=11188 Reduction of carboxylic acid to alcohol!]

[[Category:Types of chemical]]
[[Category:Organic compounds]]
[[Category:Carboxylic acids]]