Aniline
Overview
 
Aniline, phenylamine or aminobenzene is an organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 C6H5NH2. Consisting of a phenyl group
Phenyl group
In organic chemistry, the phenyl group or phenyl ring is a cyclic group of atoms with the formula C6H5. Phenyl groups are closely related to benzene. Phenyl groups have six carbon atoms bonded together in a hexagonal planar ring, five of which are bonded to individual hydrogen atoms, with the...

 attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...

. Like most volatile amines, it possesses the somewhat unpleasant odour of rotten fish.
Encyclopedia
Aniline, phenylamine or aminobenzene is an organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 C6H5NH2. Consisting of a phenyl group
Phenyl group
In organic chemistry, the phenyl group or phenyl ring is a cyclic group of atoms with the formula C6H5. Phenyl groups are closely related to benzene. Phenyl groups have six carbon atoms bonded together in a hexagonal planar ring, five of which are bonded to individual hydrogen atoms, with the...

 attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...

. Like most volatile amines, it possesses the somewhat unpleasant odour of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds. Aniline is colorless, but it slowly oxidizes and resinifies in air, giving a red-brown tint to aged samples.

Production

Aniline is mainly produced in industry in two steps from benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

. First, benzene is nitrated
Nitration
Nitration is a general chemical process for the introduction of a nitro group into a chemical compound. The dominant application of nitration is for the production of nitrobenzene, the precursor to methylene diphenyl diisocyanate...

 using a concentrated mixture of nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

 and sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

 at 50 to 60°C, which gives nitrobenzene
Nitrobenzene
Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale as a precursor to aniline. Although occasionally used as a flavoring or perfume...

. In the second step, the nitrobenzene is hydrogenated
Hydrogenation
Hydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...

, typically at 200-300 °C in presence of various metal catalysts:
C6H5NO2 + 3 H2 → C6H5NH2 + 2 H2O

Originally, the reduction was effected with a mixture of ferrous chloride and iron metal via the Bechamp reduction
Bechamp Reduction
The Bechamp reduction is used to reduce aromatic nitro compounds to their corresponding anilines, using iron and hydrochloric acid.This reaction was originally used to produce large amounts of aniline for industry, but catalytic hydrogenation is the preferred method...

.

As an alternative, aniline is also prepared from phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

 and ammonia, the phenol being derived from the cumene process
Cumene process
The Cumene process is an industrial process for developing phenol and acetone from benzene and propylene. The term stems from cumene , the intermediate material during the process. It was invented by Heinrich Hock in 1944 and independently by R. Ūdris and P...

.

In commerce, three brands of aniline are distinguished: aniline oil for blue, which is pure aniline; aniline oil for red, a mixture of equimolecular quantities of aniline and ortho- and para-toluidines; and aniline oil for safranine, which contains aniline and ortho-toluidine
Toluidine
There are three isomers of toluidine, which are organic compounds. These isomers are o-toluidine, m-toluidine, and p-toluidine. The o- stands for ortho- , m- stands for meta- , and p- stands for para-...

, and is obtained from the distillate
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....

 (échappés) of the fuchsine
Fuchsine
Fuchsine or rosaniline hydrochloride is a magenta dye with chemical formula C20H19N3·HCl. There are other similar chemical formulations of products sold as fuchsine, and several dozen other synonyms of this molecule....

 fusion.

Related aniline derivatives

Many derivatives of aniline can be prepared in similar fashion from nitrated aromatic compounds. Nitration followed by reduction of toluene
Toluene
Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...

 affords toluidine
Toluidine
There are three isomers of toluidine, which are organic compounds. These isomers are o-toluidine, m-toluidine, and p-toluidine. The o- stands for ortho- , m- stands for meta- , and p- stands for para-...

s. Nitration of chlorobenzene
Chlorobenzene
Chlorobenzene is an aromatic organic compound with the chemical formula C6H5Cl. This colorless, flammable liquid is a common solvent and a widely used intermediate in the manufacture of other chemicals.-Uses:...

 and related derivatives and reduction of the nitration products gives aniline derivatives, e.g. 4-chloroaniline
4-Chloroaniline
4-Chloroaniline is a organochlorine compound with the formula ClC6H4NH2. This pale yellow solid is one of several known chloroanilines.-Preparation:4-Chloroaniline is not prepared from aniline, which tends to overchlorinate...

.

Reactions

The chemistry of aniline is extremely rich because the compound has been cheaply available for many years. Below are some classes of its reactions.

Oxidation

The oxidation of aniline has been heavily investigated, and can result in reactions localized at nitrogen or more commonly results in the formation of new C-N bonds. In alkaline solution, azobenzene
Azobenzene
Azobenzene is a chemical compound composed of two phenyl rings linked by a N=N double bond. It is the best known example of an azo compound. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of molecules that share the core azobenzene structure, with different chemical...

 results, whereas arsenic acid
Arsenic acid
Arsenic acid is the chemical compound with the formula H3AsO4. More descriptively written as AsO3, this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as such has not been isolated, but only found in solution where it...

 produces the violet-coloring matter violaniline. Chromic acid
Chromic acid
The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of chromic acid may be used as a cleaning mixture for glass. Chromic acid may also refer to the...

 converts it into quinone
Quinone
A quinone is a class of organic compounds that are formally "derived from aromatic compounds [such as benzene or naphthalene] by conversion of an even number of –CH= groups into –C– groups with any necessary rearrangement of double bonds," resulting in "a fully conjugated cyclic dione structure."...

, whereas chlorates, in the presence of certain metallic salts (especially of vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...

), give aniline black. Hydrochloric acid and potassium chlorate give chloranil
Chloranil
Chloranil is a quinone with the molecular formula C6Cl4O2....

. Potassium permanganate
Potassium permanganate
Potassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...

 in neutral solution oxidizes it to nitrobenzene
Nitrobenzene
Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced on a large scale as a precursor to aniline. Although occasionally used as a flavoring or perfume...

, in alkaline solution to azobenzene
Azobenzene
Azobenzene is a chemical compound composed of two phenyl rings linked by a N=N double bond. It is the best known example of an azo compound. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of molecules that share the core azobenzene structure, with different chemical...

, ammonia and oxalic acid
Oxalic acid
Oxalic acid is an organic compound with the formula H2C2O4. This colourless solid is a dicarboxylic acid. In terms of acid strength, it is about 3,000 times stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations...

, in acid solution to aniline black. Hypochlorous acid
Hypochlorous acid
Hypochlorous acid is a weak acid with the chemical formula HClO. It forms when chlorine dissolves in water. It cannot be isolated in pure form due to rapid equilibration with its precursor...

 gives 4-aminophenol and para-amino diphenylamine
Diphenylamine
Diphenylamine is the organic compound with the formula 2NH. It is a colourless solid, but samples are often yellow due to oxidized impurities.-Preparation and reactivity:...

. Oxidation with persulfate affords a variety of polyaniline
Polyaniline
Polyaniline is a conducting polymer of the semi-flexible rod polymer family. Although the compound itself was discovered over 150 years ago, only since the early 1980s has polyaniline captured the intense attention of the scientific community. This is due to the rediscovery of its high electrical...

s compounds. These polymers exhibit rich redox and acid-base properties.

Electrophilic reactions at carbon

Like phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

s, aniline derivatives are highly susceptible to electrophilic substitution
Electrophilic substitution
Electrophilic substitution reactions are chemical reactions in which an electrophile displaces a group in a compound, typically but not always hydrogen. Electrophilic aromatic substitution is characteristic of aromatic compounds and is an important way of introducing functional groups onto benzene...

 reactions. Its high reactivity reflects that it is an enamine
Enamine
An enamine is an unsaturated compound derived by the reaction of an aldehyde or ketone with a secondary amine followed by loss of H2O.The word "enamine" is derived from the affix en-, used as the suffix of alkene, and the root amine. This can be compared with enol, which is a functional group...

, which enhances the electron-donating ability of the ring. For example, reaction of aniline with sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

 at 180 °C produces sulfanilic acid
Sulfanilic acid
Sulfanilic acid is a grey crystalline solid produced from sulfonation of aniline.It readily forms diazo compounds and is used to make dyes and sulpha drugs....

, H2NC6H4SO3H, which can be converted to sulfanilamide. Sulfanilamide is one of the sulfa drug
Sulfonamide (medicine)
Sulfonamide or sulphonamide is the basis of several groups of drugs. The original antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame...

s, which were widely used as antibacterials in the early 20th century. The largest scale industrial reaction of aniline involves its alkylation with formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

:
2 C6H5NH2 + CH2O → CH2(C6H4NH2)2 + H2O

The resulting diamine is the precursor to 4,4'-MDI and related diisocyanates.

Basicity

Aniline is a weak base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

. Aromatic amine
Aromatic amine
An aromatic amine is an amine with an aromatic substituent - that is -NH2, -NH- or nitrogen group attached to an aromatic hydrocarbon, whose structure usually contains one or more benzene rings. Aniline is the simplest example....

s such as aniline are, in general, much weaker bases than aliphatic amines because of the electron-withdrawing effect of the phenyl group. Aniline reacts with strong acids to form anilinium (or phenylammonium) ion (C6H5-NH3+). The sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...

 forms white plates. Although aniline is weakly basic, it precipitates zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

, aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

, and ferric
Ferric
Ferric refers to iron-containing materials or compounds. In chemistry the term is reserved for iron with an oxidation number of +3, also denoted iron or Fe3+. On the other hand, ferrous refers to iron with oxidation number of +2, denoted iron or Fe2+...

 salts, and, on warming, expels ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 from its salts. The weak basicity is due to a negative inductive effect as the lone pair on the nitrogen is partially delocalized into the pi system of the benzene ring.

Acylation

Aniline reacts with carboxylic acids or more readily with acyl chloride
Acyl chloride
In organic chemistry, an acyl chloride is an organic compound with the functional group -CO-Cl. Their formula is usually written RCOCl, where R is a side chain. They are usually considered to be reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride,...

s such as acetyl chloride
Acetyl chloride
Acetyl chloride, CH3COCl, also known as ethanoyl chloride or acyl chloride, is an acid chloride derived from acetic acid. It belongs to the class of organic compounds called acyl halides. It is a colorless liquid. Acetyl chloride does not exist in nature, because contact with water would hydrolyze...

 to give amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...

s. The amides formed from aniline are sometimes called anilides, for example CH3-CO-NH-C6H5 is acetanilide. Antifebrin (acetanilide), an anti-pyretic and analgesic, is obtained by the reaction of acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 and aniline.

N-Alkylation

N-methylation of aniline with methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

 at elevated temperatures over acid catalsts gives N-methylaniline and dimethylaniline
Dimethylaniline
N,N-Dimethylaniline is an organic chemical compound, a substituted derivative of aniline. It consists of a tertiary amine, featuring dimethylamino group attached to a phenyl group. This oily liquid is colourless when pure, but commercial samples are often yellow...

:
C6H5NH2 + 2 CH3OH → C6H4N(CH3)2 + H2O

Methyl and dimethylaniline are colourless liquids with b.p.
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....

 of 193-195 °C and 192 °C, respectively. These derivatives are of importance in the colour industry. Aniline combines directly with alkyl iodides to form secondary and tertiary amines.

Carbon disulfide derivatives

Boiled with carbon disulfide
Carbon disulfide
Carbon disulfide is a colorless volatile liquid with the formula CS2. The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non-polar solvent...

, it gives sulfocarbanilide (diphenylthiourea
Thiourea
Thiourea is an organosulfur compound of with the formula SC2 . It is structurally similar to urea, except that the oxygen atom is replaced by a sulfur atom, but the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. "Thioureas" refers to a broad...

) (CS(NHC6H5)2), which may be decomposed into phenyl isothiocyanate
Isothiocyanate
Isothiocyanate is the chemical group –N=C=S, formed by substituting sulfur for oxygen in the isocyanate group. Many natural isothiocyanates from plants are produced by enzymatic conversion of metabolites called glucosinolates. These natural isothiocyanates, such as allyl isothiocyanate, are also...

(C6H5CNS), and triphenyl guanidine
Guanidine
Guanidine is a crystalline compound of strong alkalinity formed by the oxidation of guanine. It is used in the manufacture of plastics and explosives. It is found in urine as a normal product of protein metabolism. The molecule was first synthesized in 1861 by the oxidative degradation of an...

 (C6H5N=C(NHC6H5)2).

Diazotization

Aniline and its ring-substituted derivatives react with nitrous acid
Nitrous acid
Nitrous acid is a weak and monobasic acid known only in solution and in the form of nitrite salts.Nitrous acid is used to make diazides from amines; this occurs by nucleophilic attack of the amine onto the nitrite, reprotonation by the surrounding solvent, and double-elimination of water...

 to form diazonium salts. Through these intermediates, aniline can be conveniently converted to -OH, -CN, or a halide
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...

 via Sandmeyer reaction
Sandmeyer reaction
The Sandmeyer reaction is a chemical reaction used to synthesize aryl halides from aryl diazonium salts. It is named after the Swiss chemist Traugott Sandmeyer....

s. This diazonium salt can also be reacted with NaNO2 and phenol which produces a dye which is benzeneazophenol, this process is called coupling.

Other reactions

It reacts with nitrobenzene to produce phenazine
Phenazine
Phenazine , also called azophenylene, dibenzo-p-diazine, dibenzopyrazine, and acridizine, is a dibenzo annulated pyrazine and the parent substance of many dyestuffs, such as the eurhodines, toluylene red, indulines and safranines.-Synthesis:A classic method for the synthesis of phenazine is the...

 in the Wohl-Aue reaction
Wohl-Aue reaction
The Wohl-Aue reaction is an organic reaction between an aromatic nitro compound and an aniline to form a phenazine in presence of an alkali base. An example is the reaction between nitrobenzene and aniline:The reaction is named after Alfred Wohl and W. Aue....

. Hydrogenation gives cyclohexylamine
Cyclohexylamine
Cyclohexylamine, also called hexahydroaniline, 1-aminocyclohexane, or aminohexahydrobenzene, is an organic chemical, an amine derived from cyclohexane. It is a clear to yellowish liquid with fishy odor, with melting point of −17.7 °C and boiling point 134.5 °C, miscible with water...

.

Being a standard reagent in laboratories, aniline is used for many niche reactions. Its acetate is used in the Aniline acetate test
Aniline acetate test
The aniline acetate test is a chemical test to identify the presence of certain carbohydrates. These carbohydrates may be converted to furfural, which reacts with aniline acetate to produce a bright pink color....

 for carbohydrates, identifying pentoses by conversion to furfural
Furfural
Furfural is an organic compound derived from a variety of agricultural byproducts, including corncobs, oat, wheat bran, and sawdust. The name furfural comes from the Latin word , meaning bran, referring to its usual source....

. It is used to stain neural RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 blue in the Nissl stain.

Uses

The largest application of aniline is for the preparation of methylene diphenyl diisocyanate
Methylene diphenyl diisocyanate
Methylene diphenyl diisocyanate, most often abbreviated as MDI, is an aromatic diisocyanate. It exists in three isomers, 2,2'-MDI, 2,4'-MDI, and 4,4'-MDI, but the 4,4' isomer is most widely used. This isomer is also known as Pure MDI. MDI reacts with polyols in the manufacture of polyurethane...

 (MDI). The majority of aniline serves this market. Other uses include rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

 processing chemicals (9%), herbicides (2%), and dyes and pigments (2%). As additives to rubber, aniline derivatives such as phenylenediamine
Phenylenediamine
Phenylenediamine may refer to:*o-phenylenediamine or OPD, a chemical compound C6H42*m-phenylenediamine or MPD, a chemical compound C6H42*p-phenylenediamine or PPD, a chemical compound C6H42...

and diphenylamine
Diphenylamine
Diphenylamine is the organic compound with the formula 2NH. It is a colourless solid, but samples are often yellow due to oxidized impurities.-Preparation and reactivity:...

, are antioxidants. Illustrative of the drugs prepared from aniline is paracetamol
Paracetamol
Paracetamol INN , or acetaminophen USAN , is a widely used over-the-counter analgesic and antipyretic . It is commonly used for the relief of headaches and other minor aches and pains and is a major ingredient in numerous cold and flu remedies...

 (acetaminophen, Tylenol
Tylenol
Tylenol is a North American brand of drugs advertised for reducing pain, reducing fever, and relieving the symptoms of allergies, cold, cough, and flu. The active ingredient of its original, flagship product, paracetamol , is marketed as an analgesic and antipyretic...

). The principal use of aniline in the dye industry is as a precursor to indigo
Indigo dye
Indigo dye is an organic compound with a distinctive blue color . Historically, indigo was a natural dye extracted from plants, and this process was important economically because blue dyes were once rare. Nearly all indigo dye produced today — several thousand tons each year — is synthetic...

, the blue of blue jeans
Blue Jeans
"Blue Jeans" is a sentimental popular song written by Harry D. Kerr and Lou Traveller in 1920. In the song, the singer is reminiscing about a long-ago young love that happened somewhere in the "hills of the old Cumberland." The chorus echoes the singer's longing:* The Parlor Songs Collection.* by...

.

Aniline is also used at a smaller scale in the production of the intrinsically conducting polymer polyaniline
Polyaniline
Polyaniline is a conducting polymer of the semi-flexible rod polymer family. Although the compound itself was discovered over 150 years ago, only since the early 1980s has polyaniline captured the intense attention of the scientific community. This is due to the rediscovery of its high electrical...

.

History

Aniline was first isolated from the destructive distillation of indigo
Indigo dye
Indigo dye is an organic compound with a distinctive blue color . Historically, indigo was a natural dye extracted from plants, and this process was important economically because blue dyes were once rare. Nearly all indigo dye produced today — several thousand tons each year — is synthetic...

 in 1826 by Otto Unverdorben
Otto Unverdorben
Otto Unverdorben was a German chemist and merchant who was born in Dahme/Marke. After completing his schooling in Dresden, he studied chemistry at Halle, Leipzig and Berlin....

, who named it crystalline. In 1834, Friedlieb Runge (Pogg. Ann., 1834, 31, p. 65; 32, p. 331) isolated from coal tar
Coal tar
Coal tar is a brown or black liquid of extremely high viscosity, which smells of naphthalene and aromatic hydrocarbons. Coal tar is among the by-products when coal iscarbonized to make coke or gasified to make coal gas...

 a substance that produced a beautiful blue colour on treatment with chloride of lime, which he named kyanol or cyanol. In 1841, C. J. Fritzsche showed that, by treating indigo with caustic potash, it yielded an oil, which he named aniline from the name of one of the indigo-yielding plants, Añil (Indigofera suffruticosa, syn. I. anil, ultimately from Sanskrit "nīla", dark-blue). About the same time N. N. Zinin found that, on reducing nitrobenzene, a base was formed, which he named benzidam. August Wilhelm von Hofmann
August Wilhelm von Hofmann
August Wilhelm von Hofmann was a German chemist.-Biography:Hofmann was born at Gießen, Grand Duchy of Hesse. Not intending originally to devote himself to physical science, he first took up the study of law and philology at Göttingen. But he then turned to chemistry, and studied under Justus von...

 investigated these variously-prepared substances, and proved them to be identical (1855), and thenceforth they took their place as one body, under the name aniline or phenylamine.

The great commercial value of aniline was due to the readiness with which it yields, directly or indirectly, dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

stuffs. The discovery of mauve
Mauveine
Mauveine, also known as aniline purple and Perkin's mauve, was the first synthetic organic chemical dye.Its chemical name is3-amino-2,±9-dimethyl-5-phenyl-7-phenazinium acetate...

 in 1856 by William Henry Perkin was the first of a series of an enormous range of dyestuffs, such as fuchsine, safranine and induline. Its first industrial-scale use was in the manufacture of mauveine
Mauveine
Mauveine, also known as aniline purple and Perkin's mauve, was the first synthetic organic chemical dye.Its chemical name is3-amino-2,±9-dimethyl-5-phenyl-7-phenazinium acetate...

, a purple
Purple
Purple is a range of hues of color occurring between red and blue, and is classified as a secondary color as the colors are required to create the shade....

 dye discovered in 1856 by Hofmann's student William Henry Perkin. At the time of mauveine's discovery, aniline was an expensive laboratory compound, but it was soon prepared "by the ton" using a process previously discovered by Antoine Béchamp
Antoine Béchamp
Pierre Jacques Antoine Béchamp was a French biologist. He studied silkworm parasites, and was the first to synthesise Atoxyl.-Biography:...

. The synthetic dye industry grew rapidly as new aniline-based dyes were discovered in the late 1850s and 1860s, an echo of the importance of the compound being found in the name of one of the world's largest chemical companies, BASF
BASF
BASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...

, originally the Badische Anilin- und Soda-Fabrik.

"Analin" was used as an analgesic
Analgesic
An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....

 drug in the 18th century. Its cardiac suppressing side-effects were countered with caffeine. Gelsemium
Gelsemium
Gelsemium is a genus of flowering plants belonging to family Gelsemiaceae. The genus contains three species of shrubs to straggling or twining climbers. Two species are native to North America, and one to China and Southeast Asia....

 was preferred and administered until slight ptosis
Ptosis
Ptosis refers to droopiness of a body part. Specifically, it can refer to:* Ptosis * Ptosis * Enteroptosis * Gastroptosis...

 (drooping eyelids) appeared.

Toxicology

Aniline is toxic by inhalation of the vapour. The IARC
International Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....

 lists it in Group 3 (not classifiable as to its carcinogenicity to humans) due to the limited and contradictory data available. The early manufacture of aniline resulted in increased incidents of
bladder cancer, but these effects are now attributed to naphthylamines, not anilines.

External links

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