Aniline

 Aniline was first isolated from the destructive distillation of indigo in 1826 by Otto Unverdorben,who named it crystalline.
In 1834, Friedrich Runge isolated from coal tar 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 specific name of one of the indigo-yielding plants, Indigofera anil, anil being derived from the Sanskrit nīla, dark-blue, and nīlā, the indigo plant.
About the same time N. N. Zinin found that, on reducing nitrobenzene, a base was formed, which he named benzidam. August Wilhelm von Hofmann 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.
Its first industrial-scale use was in the manufacture of mauveine, a purple 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. The synthetic dye industry grew rapidly as new aniline-based dyes were discovered in the late 1850s and 1860s.

OSHA PEL: TWA 2 ppm (skin)
ACGIH TLV: TWA 2 ppm (skin); Animal Carcinogen; BEI: 50 mg/g creatinine of total p-aminophenol in urine at end of shift or 1.5% of hemoglobin for methemoglobin in blood during or end of shift.
DFG MAK: 2 ppm (7.7 mg/m³), Confirmed Animal Carcinogen with Unknown Relevance to Humans; BAT: 1 mg/L in urine at end of shift
DOT Classification:  6.1; Label: Poison

For occupational chemical analysis use NIOSH: Amines, Aromatic, 2002.

Aniline is an organic compound with the formula C₆H₅NH₂ which has the IUPAC name Phenylamine. Its EINECS register number is 200-539-3 and CAS register number is 62-53-3. Aniline is incompatible with oxidizing agents, bases, acids, iron and iron salts, zinc, aluminium. In addition, Aniline is light sensitive and combustible. Aniline is colorless liquid with a musty fishy odor which is slightly soluble in water. Aniline will melt at temperature of -6.3 °C. It has the density of 1.0217 g/mL.

Properties: Aniline is extremely rich because the compound has been cheaply available for many years. Below are some classes of its reactions. 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. Like phenols, Aniline derivatives are highly susceptible to electrophilic substitution reactions. For example, reaction of Aniline with sulfuric acid at 180 °C produces sulfanilic acid, H₂NC₆H₄SO₃H, which can be converted to sulfanilamide. Aniline is a heat sensitive base which combines with acids to form salts.

In addition, Aniline can react vigorously with oxidizing materials such as perchloric acid, fuming nitric acid, sodium peroxide and ozone. It reacts violently with BCl₃. Meanwhile, Aniline will undergoe explosive reactions with benzenediazonium-2-carboxylate, dibenzoyl peroxide, fluorine nitrate, nitrosyl perchlorate, peroxodisulfuric acid and tetranitromethane. There will be a violent reactions if Aniline combines with peroxyformic acid, diisopropyl peroxydicarbonate, fluorine, trichloronitromethane (293 °F), acetic anhydride, chlorosulfonic acid, hexachloromelamine. Finally, Aniline will react with perchloryl fluoride form explosive products.

Production: Aniline is mainly produced by benzene in industry in two steps. In the first step, benzene is nitrated using a concentrated mixture of nitric acid and sulfuric acid at 50 to 60°C to give nitrobenzene. In the second step, the nitrobenzene is hydrogenated at 200-300 °C in presence of various metal catalysts. Many derivatives of Aniline can be prepared in similar fashion from nitrated aromatic compounds. Nitration of chlorobenzene and related derivatives and reduction of the nitration products gives aniline derivatives, e.g. 4-chloroaniline.

C₆H₆ + HNO₃ [H₂SO₄] → C₆H₅NO₂
C₆H₅NO₂ + 3 H₂ → C₆H₅NH₂ + 2 H₂O

Aniline can also be prepared by the reduction of iron powder in old method. The reactive fluid is neutralized, eluted and distilled to give end product.

4 C₆H₅NO₂ + 9 Fe + 4 H₂O → 4 C₆H₅NH₂ + 3 Fe₃O₄

Meanwhile, Aniline is also produced by ammoniation of Phenol at the temperature of 370 °C and the pressure of 1.6MPa. This reaction needs catalyst of acidic chlorine dioxide. The conversion percent is above 99% and productivity of Aniline is above 96%.

C₆H₅OH + NH₃[SiO-Al₂O₃] → C₆H₅NH₂ + H₂O

Uses: Aniline is mainly used in the manufacture of precursors to polyurethane, as a precursor to many industrial chemicals. The largest application of Aniline is for the preparation of methylene diphenyl diisocyanate (MDI). In addition, it is used to manufacture other chemicals, especially dyes, photographic chemicals, agricultural chemicals and others. Aniline is also used at a smaller scale in the production of the inherently conducting polymer polyaniline. Other uses of Aniline include rubber processing chemicals (9%), herbicides (2%), and dyes and pigments (2%). The principal use of Aniline in the dye industry is as a precursor to indigo, the blue of blue jeans.

When using Aniline, you should be very cautious. Aniline that at low level can cause damage to health. It may present an immediate or delayed danger to one or more components of the environment and may catch fire in contact with air which only need brief contact with an ignition source and has a very low flash point or evolve highly flammable gases in contact with water. Aniline is harmful by inhalation, in contact with skin and if swallowed and toxic by inhalation, in contact with skin and if swallowed. 

In case of contact with eyes, you should rinse immediately with plenty of water and seek medical advice. Whenever you will contact Aniline, you must wear suitable protective clothing, gloves and eye/face protection. In case of accident or if you feel unwell seek medical advice immediately (show the label where possible). If swallowed, you should seek medical advice immediately and show this container or label. What's more, you must avoid releasing it to the environment. When using Aniline, you can refer to special instructions/safety data sheet. In case of accident by inhalation, you can remove casualty to fresh air and keep at rest.

Toxicity of Aniline: