Amidines are

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s with the

functional group In organic chemistry, a functional group is any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions r ...

RC(NR)NR₂, where the R groups can be the same or different. They are the

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...

derivatives of

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...

s (RC(O)NR₂). The simplest amidine is formamidine, HC(=NH)NH₂. Examples of amidines include: *

DBU DBU may refer to: Universities * Dallas Baptist University, Dallas, Texas, U.S. * Desh Bhagat University, Mandi Gobindgarh, Punjab, India * Duluth Business University, Duluth, Minnesota, U.S. Other uses * 1,8-Diazabicyclo .4.0ndec-7-ene, an org ...

diminazene Diminazene (INN; also known as diminazen) is an anti-infective medication for animals that is sold under a variety of brand names. It is effective against certain protozoa such as ''Babesia'', ''Trypanosoma'', and '' Cytauxzoon''. The drug may al ...

benzamidine Benzamidine is an organic compound with the formula C6H5C(NH)NH2. It is the simplest aryl amidine. The compound is a white solid that is slightly soluble in water. It is usually handled as the hydrochloride salt, a white, water-soluble solid. ...

Pentamidine Pentamidine is an antimicrobial medication used to treat African trypanosomiasis, leishmaniasis, '' Balamuthia'' infections, babesiosis, and to prevent and treat pneumocystis pneumonia (PCP) in people with poor immune function. In African trypa ...

* Paranyline

Preparation

A common route to primary amidines is the

Pinner reaction The Pinner reaction refers to the acid catalysed reaction of a nitrile with an alcohol to form an imino ester salt (alkyl imidate salt); this is sometimes referred to as a Pinner salt. The reaction is named after Adolf Pinner, who first described ...

. Reaction of the nitrile with alcohol in the presence of acid gives an

iminoether Carboximidates (or more general imidates) are organic compounds, which can be thought of as esters formed between an imidic acid () and an alcohol, with the general formula . They are also known as imino ethers, since they resemble imines () w ...

. Treatment of the resulting compound with

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

then completes the conversion to the amidine. Instead of using a Bronsted acid,

Lewis acids A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

such as

aluminium trichloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms a hexahydrate with the formula , containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are col ...

promote the direct

amination Amination is the process by which an amine group is introduced into an organic molecule. This type of reaction is important because organonitrogen compounds are pervasive. Reactions Aminase enzymes Enzymes that catalyse this reaction are termed a ...

nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The name of the compound is composed of a base, which includes the carbon of the , suffixed with "nitrile", so for example is called " propionitrile" (or pr ...

s, or, in certain exceptional cases, of

Dimethylformamide Dimethylformamide, DMF is an organic compound with the chemical formula . Its structure is . Commonly abbreviated as DMF (although this initialism is sometimes used for 2,5-dimethylfuran, dimethylfuran, or dimethyl fumarate), this colourless liqui ...

acetal In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments n ...

reacts with primary

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

s to give amidines: :Me₂NC(H)(OMe)₂ + RNH₂ → Me₂NC=NHR + 2 MeOH Catalysis is likewise not required for direct amination of an

imidoyl chloride Imidoyl chlorides are organic compounds that contain the functional group RC(NR')Cl. A double bond exist between the R'N and the carbon centre. These compounds are analogues of acyl chloride. Imidoyl chlorides tend to be highly reactive and are m ...

. Amidines are also prepared by the addition of

organolithium reagent In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom ...

s to

diimine Diimines are organic compounds containing two imine (RCH=NR') groups. Common derivatives are 1,2-diimines and 1,3-diimines. These compounds are used as ligands, but they are also precursors to other organic compounds. Preparation Diimines are ...

s, followed by

protonation In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), usually denoted by H+, to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brø ...

alkylation Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...

Acid-base chemistry

Amidines are much more basic than amides and are among the strongest uncharged/unionized bases. Protonation occurs at the sp²-hybridized nitrogen. This occurs because the positive charge can be

delocalized In chemistry, delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond.IUPAC Gold Boo''delocalization''/ref> The term delocalization is general and can have slightly dif ...

onto both nitrogen atoms. The resulting

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

ic species is known as an amidinium ion and possesses identical C-N bond lengths. Amidineresonance

Applications

Several drug or drug candidates feature amidine substituents. Examples include the antiprotozoal

imidocarb Imidocarb is a urea derivative used in veterinary medicine as an antiprotozoal agent for the treatment of infection with ''Babesia'' ( babesiosis) and other parasites. Mechanism of action Imidocarb is anticholinergic; it inhibits acetylcholinest ...

, the

insecticide Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...

amitraz Amitraz (development code BTS27419) is a non-systemic acaricide and insecticideCorta, E., Bakkali, A., Berrueta, L. A., Gallo, B., & Vicente, F. (1999). Kinetics and mechanism of amitraz hydrolysis in aqueous media by HPLC and GC-MS. Talanta, 48(1 ...

xylamidine Xylamidine is a drug which acts as an antagonist of the serotonin 5-HT2A and 5-HT2C receptors, and to a lesser extent of the serotonin 5-HT1A receptor. The drug does not cross the blood–brain barrier and hence is peripherally selective, wh ...

, an

antagonist An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.anthelmintic Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms (helminths) and other internal parasites from the body by either stunning or killing them without causing significant damage to the host. They may also ...

s amidantel and

tribendimidine Tribendimidine is a broad-spectrum anthelmintic agent developed in China, at the National Institute of Parasitic Diseases in Shanghai. It is a derivative of amidantel.

. Formamidinium (see below) may be reacted with a metal halide to form the light-absorbing semiconducting material in

perovskite solar cell A perovskite solar cell (PSC) is a type of solar cell that includes a perovskite-structured compound, most commonly a hybrid organic–inorganic lead or tin halide-based material as the light-harvesting active layer. Perovskite materials, such a ...

s. Formamidinium (FA) cations or halides may partially or fully replace

methylammonium halide Methylammonium halides are organic halides with a formula of , where X is F for methylammonium fluoride, Cl for methylammonium chloride, Br for methylammonium bromide, or I for methylammonium iodide. Generally they are white or light colored p ...

s in forming perovskite absorber layers in photovoltaic devices.

Nomenclature

Formally, amidines are a class of

oxoacid An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bonded to oxygen that can dissociate to produce ...

s. The oxoacid from which an amidine is derived must be of the form R_''n''E(=O)OH, where R is a

substituent In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. The suffix ''-yl'' is used when naming organic compounds that contain a single bond r ...

. The −OH group is replaced by an −NH₂ group and the =O group is replaced by = N R, giving amidines the general structure R_''n''E(=NR)NR₂. When the parent oxoacid is a

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

, the resulting amidine is a carboxamidine or carboximidamide (

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

name). Carboxamidines are frequently referred to simply as amidines, as they are the most commonly encountered type of amidine in

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

Derivatives

Formamidinium cations

A notable subclass of amidinium ions are the formamidinium

s; which can be represented by the chemical formula .

Deprotonation Deprotonation (or dehydronation) is the removal (transfer) of a proton (or hydron, or hydrogen cation), (H+) from a Brønsted–Lowry acid in an acid–base reaction.Henry Jakubowski, Biochemistry Online Chapter 2A3, https://employees.csbsju.ed ...

of these gives

stable carbene A persistent carbene (also known as stable carbene) is an organic molecule whose natural resonance structure has a carbon atom with incomplete octet (a carbene), but does not exhibit the tremendous instability typically associated with such moiet ...

s which can be represented by the chemical formula .

Amidinate salts

An amidinate salt has the general structure M⁺ NRCNRsup>− and can be accessed by reaction of a

carbodiimide In organic chemistry, a carbodiimide (systematic IUPAC name: methanediimine) is a functional group with the formula RN=C=NR. On Earth they are exclusively synthetic, but in interstellar space the parent compound HN=C=NH has been detected by its ...

with an

organometallic compound Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and ...

such as

methyl lithium Methyllithium is the simplest organolithium reagent, with the empirical formula LiCH3. This s-block organometallic compound adopts an oligomeric structure both in solution and in the solid state. This highly reactive compound, invariably used in ...

. They are used widely as ligands in organometallic complexes.

References

{{Authority control Functional groups Superbases