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Carboxyl group

 

 
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Carboxyl group
 
 
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A carboxyl group is a set of four atoms bonded together and present in carboxylic acid
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
s, including amino acids
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
. Usually abbreviated as either CO2H or COOH, this set of atoms constitutes a functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
. In every carboxyl group the carbon atom is attached to an oxygen atom by a double bond and to a hydroxyl group (OH) by a single bond. In this way a carboxyl group is equivalent to a carbonyl group bonded to a hydroxyl
Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
 group.

The acidic nature of a carboxyl group arises from its H atom.






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A carboxyl group is a set of four atoms bonded together and present in carboxylic acid
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
s, including amino acids
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
. Usually abbreviated as either CO2H or COOH, this set of atoms constitutes a functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
. In every carboxyl group the carbon atom is attached to an oxygen atom by a double bond and to a hydroxyl group (OH) by a single bond. In this way a carboxyl group is equivalent to a carbonyl group bonded to a hydroxyl
Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
 group.

The acidic nature of a carboxyl group arises from its H atom. Specifically, in aqueous solution the H atom can be transferred as H+ to H2O molecules, forming H3O+ and leaving behind a COO– group. For example, the H atom in the carboxyl group of acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
 (CH3COOH) reacts with H2O to make H3O+ and the acetate
Acetate

An acetate, or ethanoate, is either a salt or ester of acetic acid.In chemistry, the abbreviation Ac refers to the acetyl group. The anion and the functional group may be written as -OAc and AcO-, or OAc respectively....
 ion: CH3COOH + H2O ? H3O+ + CH3COO–.

The drawings on this page show a carboxyl group bonding to an atom, or a groups of atoms, through its own carbon. In these representations, "R" symbolizes the atom or atoms to which bonding occurs. As examples, R = H for HCOOH, formic acid
Formic acid

Formic acid is the simplest carboxylic acid. Its formula is hydrogencarbonoxygenOH or CH2O2. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stingers....
, but R = CH3 for acetic acid, CH3COOH.

The COOH group has only a separate fleeting existence when not bonded to a fifth atom. In such cases it is called the carboxyl radical and symbolized as •COOH. See, for example, the study by Milligan and Jacox. The acid dissociation constant
Acid dissociation constant

An acid dissociation constant, Ka, is a quantitative measure of the strong acid in solution. It is the equilibrium constant for a chemical reaction known as Dissociation in the context of acid-base reactions....
 of COOH has been measured using electron paramagnetic resonance
Electron paramagnetic resonance

Electron paramagnetic resonance or electron spin resonance spectroscopyis a technique for studying chemical species that have one or more unpaired electrons, such as organic and inorganic free radicals or inorganic chemistry complex possessing a transition metal ion....
 spectrocopy.

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