Zwitterion

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Zwitterion

A zwitterion (first part pronounced "tsvitter", from German

German language

German is a West Germanic languages, thus related to and classified alongside English language and Dutch language. It is one of the world's world language and the most widely spoken mother tongue in the European Union....
"Zwitter" — "hybrid," "hermaphrodite

Hermaphrodite

A hermaphrodite is an organism having both male and female reproductive organs. In many species, hermaphroditism is a common part of the life-cycle, enabling a form of sexual reproduction in which partners are not separated into distinct male and female types of individual....
") is a chemical compound

Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
that carries a total net charge of 0, thus electrically neutral but carries formal positive and negative charges

Formal charge

In chemistry, a formal charge is a partial charge on an atom in a molecule assigned by assuming that electrons in a chemical bond are shared equally between atoms, regardless of relative electronegativity or in another definition the charge remaining on an atom when all ligands are removed homolysis ....
on different atom

Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s. Some chemists restrict this term to refer to compounds with non-adjacent positive and negative charges. This would exclude compounds such as N-oxides. Zwitterions are polar

Chemical polarity

In chemistry, polarity refers to the dipole-dipole intermolecular forces between the slightly electric charge end of one molecule to the negative end of another or the same molecule....
and are usually very water-soluble, but poorly soluble in most organic solvents.

Ampholytes are molecules that contain both acid

Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
ic and basic

Base (chemistry)

In chemistry, a base is most commonly thought of as an aqueous substance that can accept protons. A base is also often referred to as an alkali if OH- ions are involved....
groups (and are therefore amphoteric

Amphoterism

In chemistry, an amphoteric substance is one that can react as either an acid or base . The word is derived from the Greek prefix ampho- meaning "both"....
) and will exist mostly as zwitterions in a certain range of pH

pH is a measure of the Acid or Base of a solution. It is defined as the cologarithm of the Activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations....
.

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Applications

Ampholytes are used to establish a stable pH gradient for use in isoelectric focusing

Isoelectric focusing

Isoelectric focusing , also known as electrofocusing, is a technique for separating different molecules by their electric charge differences....
.

Typical examples of zwitterions are:

Most amino acid
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....
s at physiological pH are for the most part zwitterionic.
Used as buffering agent
Buffering agent

A buffering agent adjusts the pH of a solution. The function of a buffering agent is to drive an acidic or basic solution to a certain pH state and prevent a change in this pH....
s in Good's buffers
Good's buffers

Good's buffers are twelve buffering agents selected and described by Norman Good and colleagues in 1966. Good selected the buffers based on a number of criteria which make them candidates for use in biochemistry and biology research....
:

The amino-sulfonic acid
Sulfonic acid

Sulfonic acid usually refers to a member of the class of organic acids with the general formula R-S2-OH, where R is usually a hydrocarbon side chain....
based MES
MES (buffer)

MES is the common name for the compound 2-ethanesulfonic acid. Its chemical structure contains a morpholine ring. It has a molecular weight of 195.2 and the chemical formula is C6H13NO4S....
, MOPS
MOPS

MOPS is the common name for the compound 3-propanesulfonic acid a buffer introduced by Good et al. in the 1960s. It is a structural analog to MES ....
, HEPES
HEPES

HEPES is a zwitterionic organic chemical buffering agent; one of the twelve Good's buffers. HEPES is widely used in cell culture, largely because it is better at maintaining physiological pH despite changes in carbon dioxide concentration when compared to bicarbonate buffers, which are also commonly used in cell culture....
, PIPES
PIPES

PIPES is the common name for piperazine-N,N'-bis, a frequently used buffering agent in biochemistry. It is an ethanesulfonic acid buffer developed by Good et al in the 1960s....
or CAPS
CAPS (buffer)

CAPS is the common name for N-cyclohexyl-3-aminopropanesulfonic acid, a chemical used as buffering agent in biochemistry. The similar substance N-cyclohexyl-2-hydroxyl3-aminopropanesulfonic acid CAPSO is also used as buffering agent in biochemistry....
The amino-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....
(amino acid
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....
) based glycine
Glycine

Glycine is the organic compound with the chemical formula NH2CH2COOH. It is the smallest of the 20 amino acids commonly found in proteins, coded by codons GGU, GGC, GGA and GGG....
, its derivatives bicine
Bicine

Bicine is an organic compound used as a buffering agent. It is one of Good's buffers and has a pKa of 8.35 at 20 ?C....
and tricine
Tricine

Tricine is an organic compound that is used in buffer solutions. The name tricine comes from tris and glycine from which it was derived. It is a zwitterionic amino acid with a useful buffering range of pH 7.4-8.8....
, and alanine
Alanine

Alanine is an a-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 proteinogenic amino acids, i.e. the building blocks of proteins....

Used as detergent
Detergent

A detergent is a material intended to assist cleaning. The term is sometimes used to differentiate between soap and other surfactants used for cleaning....
s:

CHAPSO

Natural products like the alkaloid
Alkaloid

Alkaloids are naturally occurring chemical compounds containing base nitrogen atoms. The name derives from the word alkaline and was used to describe any nitrogen-containing base....
s psilocybin
Psilocybin

Psilocybin is a psychedelic drug indole of the tryptamine family, found in psilocybin mushrooms. It is present in List of Psilocybin mushrooms of fungi, including those of the genus Psilocybe, such as Psilocybe cubensis and liberty cap , but also reportedly isolated from a dozen or so other genera....
and lysergic acid
Lysergic acid

Lysergic acid, also known as D-lysergic acid and -lysergic acid, is a precursor for a wide range of ergoline alkaloids that are produced by the ergot fungus and some plants....
.
Betaines
Betaines

A betaine in chemistry is any neutral chemical compound with a positively charged cationic functional group such as an ammonium ion or phosphonium ion which bears no hydrogen atom and with a negatively charged functional group such as a carboxylate group which may not be adjacent to the cationic site....

Less common examples of zwitterions are:

Quinonoid zwitterion
Quinonoid zwitterion

A Quinonoid zwitterion is a special type of zwitterion based on quinone related chemical compounds. The benzene derivate 1,3-dihydroxy-4,6-diaminobenzene is easily organic oxidation by air in water or methanol to the quinonoid....
s.
Drugs such as Fexofenadine
Fexofenadine

Fexofenadine hydrochloride is an antihistamine medication used in the treatment of hayfever and similar allergy symptoms. It was developed as a successor of and alternative to terfenadine , an antihistamine with potentially serious contraindications....
(Allegra) and Cephaloridine.
decaphenylferrocene [(?⁵-C₅Ph₅)₂Fe] has been shown to have a zwitterionic linkage isomer
Linkage isomerism

Linkage isomerism is the existence of Complex s that have the same composition differing with the connectivity of the metal to a ligand....
[(?⁵-C₅Ph₅)Fe⁺(?⁶-C₆H₅C₅Ph₄⁻)].