Carboxylic acid

Structure of a carboxylic acid
Carboxylate Anion
3D structure of a carboxylic acid

A carboxylic acid k/ is an organic compound that contains a carboxyl group (C(=O)OH).[1] The general formula of a carboxylic acid is R–COOH, with R referring to the rest of the (possibly quite large) molecule. Carboxylic acids occur widely and include the amino acids (which make up proteins) and acetic acid (which is part of vinegar and occurs in metabolism).

Salts and esters of carboxylic acids are called carboxylates. When a carboxyl group is deprotonated, its conjugate base forms a carboxylate anion. Carboxylate ions are resonance-stabilized, and this increased stability makes carboxylic acids more acidic than alcohols, along with the electron-withdrawing effect of the carbonyl bond, which makes the terminal oxygen-hydrogen bond weaker and thus makes acid dissociation more favorable (lowers pKa).

Carboxylic acids can be seen as reduced or alkylated forms of the Lewis acid carbon dioxide; under some circumstances they can be decarboxylated to yield carbon dioxide.

Example carboxylic acids and nomenclature

Carboxylic acids are commonly identified using their trivial names, and usually have the suffix -ic acid. IUPAC-recommended names also exist; in this system, carboxylic acids have an -oic acid suffix.[2] For example, butyric acid (C3H7CO2H) is butanoic acid by IUPAC guidelines. The -oic acid nomenclature detail is based on the name of the previously-known chemical benzoic acid.[citation needed] For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, for example, 3-chloropropanoic acid. Alternately, it can be named as a "carboxy" or "carboxylic acid" substituent on another parent structure, for example, 2-carboxyfuran.

The carboxylate anion (R–COO) of a carboxylic acid is usually named with the suffix -ate, in keeping with the general pattern of -ic acid and -ate for a conjugate acid and its conjugate base, respectively. For example, the conjugate base of acetic acid is acetate.

Straight-chain, saturated carboxylic acids
Carbon
atoms
Common name IUPAC name Chemical formula Common location or use
1 Carbonic acid Carbonic acid OHCOOH Blood and tissues (bicarbonate buffer system)
1 Formic acid Methanoic acid HCOOH Insect stings
2 Acetic acid Ethanoic acid CH3COOH Vinegar
3 Propionic acid Propanoic acid CH3CH2COOH Preservative for stored grains, body odour
4 Butyric acid Butanoic acid CH3(CH2)2COOH Butter
5 Valeric acid Pentanoic acid CH3(CH2)3COOH Valerian
6 Caproic acid Hexanoic acid CH3(CH2)4COOH Goat fat
7 Enanthic acid Heptanoic acid CH3(CH2)5COOH
8 Caprylic acid Octanoic acid CH3(CH2)6COOH Coconuts
9 Pelargonic acid Nonanoic acid CH3(CH2)7COOH Pelargonium
10 Capric acid Decanoic acid CH3(CH2)8COOH Coconut and Palm kernel oil
11 Undecylic acid Undecanoic acid CH3(CH2)9COOH
12 Lauric acid Dodecanoic acid CH3(CH2)10COOH Coconut oil and hand wash soaps
13 Tridecylic acid Tridecanoic acid CH3(CH2)11COOH
14 Myristic acid Tetradecanoic acid CH3(CH2)12COOH Nutmeg
15 Pentadecylic acid Pentadecanoic acid CH3(CH2)13COOH
16 Palmitic acid Hexadecanoic acid CH3(CH2)14COOH Palm oil
17 Margaric acid Heptadecanoic acid CH3(CH2)15COOH
18 Stearic acid Octadecanoic acid CH3(CH2)16COOH Chocolate, waxes, soaps, and oils
19 Nonadecylic acid Nonadecanoic acid CH3(CH2)17COOH Fats, vegetable oils, pheromone
20 Arachidic acid Icosanoic acid CH3(CH2)18COOH Peanut oil
Other carboxylic acids
Compound class Members
unsaturated monocarboxylic acids acrylic acid (2-propenoic acid) – CH2=CHCOOH, used in polymer synthesis
Fatty acids medium to long-chain saturated and unsaturated monocarboxylic acids, with even number of carbons, examples: docosahexaenoic acid and eicosapentaenoic acid (nutritional supplements)
Amino acids the building-blocks of proteins
Keto acids acids of biochemical significance that contain a ketone group, examples: acetoacetic acid and pyruvic acid
Aromatic carboxylic acids containing at least one aromatic ring, examples: benzoic acid – the sodium salt of benzoic acid is used as a food preservative, salicylic acid – a beta hydroxy type found in many skin-care products, phenyl alkanoic acids – the class of compounds where a phenyl group is attached to a carboxylic acid
Dicarboxylic acids containing two carboxyl groups, examples: adipic acid the monomer used to produce nylon and aldaric acid – a family of sugar acids
Tricarboxylic acids containing three carboxyl groups, examples: citric acid – found in citrus fruits and isocitric acid
Alpha hydroxy acids containing a hydroxy group, examples: glyceric acid, glycolic acid and lactic acid (2-hydroxypropanoic acid) – found in sour milk, tartaric acid – found in wine
Divinylether fatty acids containing a doubly unsaturated carbon chain attached via an ether bond to a fatty acid, found in some plants
Other Languages
Afrikaans: Karboksielsuur
беларуская (тарашкевіца)‎: Карбонавыя кісьлі
Deutsch: Carbonsäuren
føroyskt: Carboxylsýra
한국어: 카복실산
Bahasa Indonesia: Asam alkanoat
latviešu: Karbonskābes
magyar: Karbonsavak
Bahasa Melayu: Asid karboksilik
Nederlands: Carbonzuur
日本語: カルボン酸
norsk nynorsk: Karboksylsyre
oʻzbekcha/ўзбекча: Karbon kislotalar
română: Acid carboxilic
Simple English: Carboxylic acid
slovenščina: Karboksilna kislina
srpskohrvatski / српскохрватски: Karboksilna kiselina
Basa Sunda: Asam karboksilat
svenska: Karboxylsyror
українська: Карбонові кислоти
Tiếng Việt: Axit cacboxylic
文言: 羧酸
粵語: 羧酸
中文: 羧酸