A report on Aniline

Ball-and-stick model of aniline from the crystal structure at 252 K
Sample of 2,6-diisopropylaniline, a colorless liquid, illustrating the tendency of anilines to air-oxidize to dark-colored products.
Polyanilines can form upon oxidation of aniline.
Aniline can react with bromine even in room temperatures in water. Acetyl chloride is added to prevent tribromination.
The nitrogen's electron was delocalized to the ring. This is why that aniline is less basic than most amines.
Cake of indigo dye, which is prepared from aniline.

Organic compound with the formula C6H5NH2.

- Aniline
Ball-and-stick model of aniline from the crystal structure at 252 K

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Nitrobenzene

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Organic compound with the chemical formula C6H5NO2.

Organic compound with the chemical formula C6H5NO2.

It is produced on a large scale from benzene as a precursor to aniline.

August Wilhelm von Hofmann

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German chemist who made considerable contributions to organic chemistry.

German chemist who made considerable contributions to organic chemistry.

Hofmann, 1846
Hofmann at the Inauguration of the School of Chemistry in London. Chimistes Celebres, Liebig's Extract of Meat Company Trading Card, 1929
Hofmann's methane model
Hofmann voltameter
Monument to Hofmann at Berlin, destroyed in 1944 by British air raid

His research on aniline helped lay the basis of the aniline-dye industry, and his research on coal tar laid the groundwork for his student Charles Mansfield's practical methods for extracting benzene and toluene and converting them into nitro compounds and amines.

Fuming nitric acid contaminated with yellow nitrogen dioxide

Nitric acid

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Inorganic compound with the formula HNO3.

Inorganic compound with the formula HNO3.

Fuming nitric acid contaminated with yellow nitrogen dioxide
Two major resonance representations of HNO3
Nitric acid in a laboratory

The nitro group can be reduced to give an amine group, allowing synthesis of aniline compounds from various nitrobenzenes:

Nitration

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General class of chemical processes for the introduction of a nitro group into an organic compound.

General class of chemical processes for the introduction of a nitro group into an organic compound.

The direct nitration of aniline with nitric acid and sulfuric acid, according to one source, results in a 50/50 mixture of para- and meta-nitroaniline isomers.

Kekulé's 1872 modification of his 1865 theory, illustrating rapid alternation of double bonds Critics pointed out a problem with Kekulé's original (1865) structure for benzene: Whenever benzene underwent substitution at the ortho position, two distinguishable isomers should have resulted, depending on whether a double bond or a single bond existed between the carbon atoms to which the substituents were attached; however, no such isomers were observed.  In 1872, Kekulé suggested that benzene had two complementary structures and that these forms rapidly interconverted, so that if there were a double bond between any pair of carbon atoms at one instant, that double bond would become a single bond at the next instant (and vice versa).  To provide a mechanism for the conversion process, Kekulé proposed that the valency of an atom is determined by the frequency with which it collided with its neighbors in a molecule.  As the carbon atoms in the benzene ring collided with each other, each carbon atom would collide twice with one neighbor during a given interval and then twice with its other neighbor during the next interval.  Thus, a double bond would exist with one neighbor during the first interval and with the other neighbor during the next interval.  Therefore, between the carbon atoms of benzene there were no fixed (i.e., constant) and distinct single or double bonds; instead, the bonds between the carbon atoms were identical.  See pages 86–89  of Auguste Kekulé (1872) "Ueber einige Condensationsprodukte des Aldehyds" (On some condensation products of aldehydes), Liebig's Annalen der Chemie und Pharmacie, 162(1): 77–124, 309–320.  From p. 89:  "Das einfachste Mittel aller Stöße eines Kohlenstoffatoms ergiebt sich aus der Summe der Stöße der beiden ersten Zeiteinheiten, die sich dann periodisch wiederholen.  … man sieht daher, daß jedes Kohlenstoffatom mit den beiden anderen, … daß diese Verschiedenheit nur eine scheinbare, aber keine wirkliche ist." (The simplest average of all the collisions of a carbon atom [in benzene] comes from the sum of the collisions during the first two units of time, which then periodically repeat.  … thus one sees that each carbon atom collides equally often with the two others against which it bumps, [and] thus stands in exactly the same relation with its two neighbors.  The usual structural formula for benzene expresses, of course, only the collisions that occur during one unit of time, thus during one phase, and so one is led to the view [that] doubly substituted derivatives [of benzene] must be different at positions 1,2 and 1,6 [of the benzene ring].  If the idea [that was] just presented—or a similar one—can be regarded as correct, then [it] follows therefrom that this difference [between the bonds at positions 1,2 and 1,6] is only an apparent [one], not a real [one].)

Benzene

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Organic chemical compound with the molecular formula C6H6.

Organic chemical compound with the molecular formula C6H6.

Kekulé's 1872 modification of his 1865 theory, illustrating rapid alternation of double bonds Critics pointed out a problem with Kekulé's original (1865) structure for benzene: Whenever benzene underwent substitution at the ortho position, two distinguishable isomers should have resulted, depending on whether a double bond or a single bond existed between the carbon atoms to which the substituents were attached; however, no such isomers were observed.  In 1872, Kekulé suggested that benzene had two complementary structures and that these forms rapidly interconverted, so that if there were a double bond between any pair of carbon atoms at one instant, that double bond would become a single bond at the next instant (and vice versa).  To provide a mechanism for the conversion process, Kekulé proposed that the valency of an atom is determined by the frequency with which it collided with its neighbors in a molecule.  As the carbon atoms in the benzene ring collided with each other, each carbon atom would collide twice with one neighbor during a given interval and then twice with its other neighbor during the next interval.  Thus, a double bond would exist with one neighbor during the first interval and with the other neighbor during the next interval.  Therefore, between the carbon atoms of benzene there were no fixed (i.e., constant) and distinct single or double bonds; instead, the bonds between the carbon atoms were identical.  See pages 86–89  of Auguste Kekulé (1872) "Ueber einige Condensationsprodukte des Aldehyds" (On some condensation products of aldehydes), Liebig's Annalen der Chemie und Pharmacie, 162(1): 77–124, 309–320.  From p. 89:  "Das einfachste Mittel aller Stöße eines Kohlenstoffatoms ergiebt sich aus der Summe der Stöße der beiden ersten Zeiteinheiten, die sich dann periodisch wiederholen.  … man sieht daher, daß jedes Kohlenstoffatom mit den beiden anderen, … daß diese Verschiedenheit nur eine scheinbare, aber keine wirkliche ist." (The simplest average of all the collisions of a carbon atom [in benzene] comes from the sum of the collisions during the first two units of time, which then periodically repeat.  … thus one sees that each carbon atom collides equally often with the two others against which it bumps, [and] thus stands in exactly the same relation with its two neighbors.  The usual structural formula for benzene expresses, of course, only the collisions that occur during one unit of time, thus during one phase, and so one is led to the view [that] doubly substituted derivatives [of benzene] must be different at positions 1,2 and 1,6 [of the benzene ring].  If the idea [that was] just presented—or a similar one—can be regarded as correct, then [it] follows therefrom that this difference [between the bonds at positions 1,2 and 1,6] is only an apparent [one], not a real [one].)
Historic benzene structures (from left to right) by Claus (1867), Dewar (1867), Ladenburg (1869), Armstrong (1887), Thiele (1899) and Kekulé (1865). Dewar benzene and prismane are distinct molecules that have Dewar's and Ladenburg's structures. Thiele and Kekulé's structures are used today.
The various representations of benzene.
Friedel-Crafts acylation of benzene by acetyl chloride
A bottle of benzene. The warnings show benzene is a toxic and flammable liquid.
The ouroboros, Kekulé's inspiration for the structure of benzene.

Examples of simple benzene derivatives are phenol, toluene, and aniline, abbreviated PhOH, PhMe, and PhNH2, respectively.

Amide formation

Amine

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In organic chemistry, amines (, UK also ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair.

In organic chemistry, amines (, UK also ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair.

Amide formation

Important amines include amino acids, biogenic amines, trimethylamine, and aniline; see for a list of amines.

William Perkin (1838–1907)

William Henry Perkin

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William Perkin (1838–1907)
Professor Charles Rees wearing a bow tie dyed with an original sample of mauveine while holding a Royal Society of Chemistry journal named after Perkin
Blue plaque in Cable Street
Section of Coal Tar Colour Works at Greenford
Perkin's gravestone
Blue plaque in Greenford, England, near the Grand Union Canal
The craze for aniline dyes, satirised in this George du Maurier cartoon

Sir William Henry Perkin (12 March 1838 – 14 July 1907) was a British chemist and entrepreneur best known for his serendipitous discovery of the first commercial synthetic organic dye, mauveine, made from aniline.

BASF

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German multinational chemical company and the largest chemical producer in the world.

German multinational chemical company and the largest chemical producer in the world.

BASF Werk in Ludwigshafen, 1865
BASF Werk in Ludwigshafen, 1881
BASF main laboratory in Ludwigshafen, 1887
Indigo production at BASF in 1890
Company scrip from Badische Anilin- & Soda-Fabrik, 2 Pfennig Gutschein, ca. 1918
Former BASF headquarters building in Ludwigshafen
BASF Portsmouth Site in the West Norfolk area of Portsmouth, Virginia, United States. The plant is served by the Commonwealth Railway.
BASF visitor center, Ludwigshafen, Germany
BASF-sponsored Museum for Laquerware in Münster, Germany
BASF in Ludwigshafen
Ludwigshafen production site at night.

The discovery in 1857 by William Henry Perkin that aniline could be used to make intense colouring agents had led to the commercial production of synthetic dyes in England from aniline extracted from coal tar.

Letter from Perkin's son, with a sample of dyed silk

Mauveine

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One of the first synthetic dyes.

One of the first synthetic dyes.

Letter from Perkin's son, with a sample of dyed silk
Professor Charles Rees—wearing a bow tie dyed with an original sample of mauveine—holding an RSC journal named after Perkin
skeletal formula of mauveine A
skeletal formula of mauveine B
skeletal formula of mauveine B2
skeletal formula of mauveine C

Its organic synthesis involves dissolving aniline, p-toluidine, and o-toluidine in sulfuric acid and water in a roughly 1:1:2 ratio, then adding potassium dichromate.

Antoine Béchamp

Antoine Béchamp

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French scientist now best known for breakthroughs in applied organic chemistry and for a bitter rivalry with Louis Pasteur.

French scientist now best known for breakthroughs in applied organic chemistry and for a bitter rivalry with Louis Pasteur.

Antoine Béchamp

Béchamp developed the Béchamp reduction, an inexpensive method to produce aniline dye, permitting William Henry Perkin to launch the synthetic-dye industry.