Carboxylic Acid

Carboxylic acids are Organic Acid s characterized by the presence of a Carboxyl Group , which has the Formula -C(=O)-OH, usually written as '''-COOH'''. In general, the Salt s and Anion s of carboxylic acids are called '''carboxylates'''.

The simplest series of carboxylic acids are the alkanoic acids, R-COOH, where R is a Hydrogen or an Alkyl Group . Compounds may also have two or more carboxylic acid groups per molecule.

ACIDITY, ELECTRON DISTRIBUTION AND RESONANCE

Carboxylic acids are widespread in nature. Carboxylic acids are typically Weak Acid s that partially Dissociate into H⁺ Cation s and RCOO⁻ Anion s in Aqueous solution. For example, only about 0.02% of all Acetic Acid molecules are dissociated at room temperature in solution.

The two Electronegative oxygen atoms tend to pull the electron away from the hydrogen of the Hydroxyl group, and the remaining Proton H⁺ 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 presence of electronegative groups (such as - OH or - Cl ) next to the carboxylic group increases the acidity. So, for example, Trichloroacetic Acid (three -Cl groups) is a stronger acid than Lactic Acid (one -OH group) which in turn is stronger than acetic acid (no helping group).

SYNTHESIS

Carboxylic acids can be prepared in the laboratory by various methods:

Complete Oxidation of Primary Alcohols and Aldehydes . This can be done with the Jones Reagent or Tollens' Reagent .

Alkene oxidation by Potassium Permanganate .

Alkylbenzene oxidation of Potassium Permanganate to Benzoic Acid s.

Acid or base Hydrolysis of Nitrile s.

Hydrolysis of Amide s and Ester s.

Carbonylation (reaction with Carbon Dioxide ) of Grignard Reagent s.

Disproportionation of an Aldehyde in the Cannizzaro Reaction .

Rearrangement of diketones in the Benzilic Acid Rearrangement .

Less-common reactions involving the generation of benzoic acids are the Von Richter Reaction from nitrobenzenes and the Kolbe-Schmitt Reaction from Phenol s.

REACTIONS

Carboxylic acids react with Bases to form carboxylate salts, in which the hydrogen of the -OH group is replaced with a metal Ion . Thus, ethanoic acid (the same as acetic acid) reacts with Sodium Bicarbonate (baking soda) to form sodium ethanoate (sodium acetate), Carbon Dioxide , and water: CH₃COOH + NaHCO₃ → CH₃COONa + CO₂ + H₂O

Carboxyl groups also react with Amine groups to form Peptide Bond s and with Alcohol s to form Ester s in Fischer Esterification or the Mitsunobu Reaction .

Carboxylic acids react with Thionyl Chloride (SOCl₂) to form Acyl Chloride s. These are extremely reactive and useful to synthesize other organic compounds.

Carboxylic acids can be Reduced by LiAlH₄ to form primary Alcohol s, although this reaction can be sluggish, as a first step is often formation of the lithium carboxylate salt. Another Reducing Agent for this reaction is Borane .

Reduction

Carboxylic Acid

Alcohol

The Arndt-Eistert Synthesis inserts an α-methylene group into a carboxylic acid.

The Curtius Rearrangement converts carboxylic acids to Isocyanate s.

Carboxylic acids are decarboxylated in the Hunsdiecker Reaction and α-brominated in the Hell-Volhard-Zelinsky Halogenation .

NOMENCLATURE AND EXAMPLES

The carboxylate anion R-COO^– is usually named with the suffix -ate, so acetic acid, for example, becomes acetate ion. In IUPAC Nomenclature , carboxylic acids have an ''' -oic Acid ''' suffix (e.g. octadecanoic acid). In Common Nomenclature , the suffix is usually '''-ic''' (e.g. stearic acid).

Some representative carboxylic acids include:

Formic Acid (methanoic acid) – HCOOH, found in insect stings (''formic'' refers to Ant s)

Acrylic Acid (ethenoic acid) - CH₂=CHCOOH, used in polymer synthesis

Lactic Acid (2-hydroxypropanoic acid) - found in sour milk

Amino Acid s – the building blocks of Protein s

Valproic Acid (2-propylpentanoic acid) - pharmaceutical

Fatty Acid s - where R is an Alkane in saturated acids or an Alkene in unsaturated acids

--- Acetic Acid (ethanoic acid) – CH₃COOH, the principal component of Vinegar

--- Propionic Acid (propanoic acid) - CH₃CH₂COOH

--- Butyric Acid (butanoic acid) – found in rancid butter

--- Lauric Acid (dodecanoic acid) – found in coconut oil

--- Docosahexaenoic Acid - nutritional supplement

--- Eicosapentaenoic Acid - nutritional supplement

Aromatic carboxylic acids

--- Benzoic Acid - C₆H₅COOH. Sodium benzoate, the sodium salt of benzoic acid is used as a food preservative

--- Salicylic Acid - found in many skin care products

Diacids

--- Aldaric Acid - a family of sugar acids

--- Oxalic Acid - found in many foods

--- Malonic Acid

--- Malic Acid - found in apples

--- Succinic Acid - a component of the Citric Acid Cycle

--- Glutaric Acid

--- Adipic Acid - the monomer used to produce nylon

Triacids

--- Citric Acid - found in Citrus Fruit s

	APPAREL
	BABY
	BEAUTY
	BOOKS
	CAR TOYS
	CELL PHONES
	DVD'S
	ELECTRONICS
	GOURMET FOOD
	GROCERIES
	HEALTH & PERSONAL
	HOME & GARDEN
	JEWELRY
	MUSIC
	MUSIC INSTRUMENTS
	OFFICE PRODUCTS
	SOFTWARE
	SPORTING GOODS
	TOOLS & HARDWARE
	TOYS
	VIDEO GAMES
	SHOPPING HOME

	MORE SHOPPING...

	CATEGORIES ABOUT CARBOXYLIC ACID

	carboxylic acids

	functional groups

	acids

Information About

Carboxylic Acid