Nitroaniline

The Nitro Aniline ( rare: nitranilines, Aminonitrobenzole ) are aromatic compounds which are derived from both the aniline and nitrobenzene from. Using different locations (ortho, meta or para) of the substituents are three structural isomers with molecular formula C6H6N2O2 result.

Representation

3- nitro- aniline may be obtained by:

• Reduction of 1,3 -dinitrobenzene with sodium sulfide in aqueous solution

2- nitroaniline can be obtained along with 4 -nitroaniline by:

• Nitration and hydrolysis of acetanilide ( a protecting group is necessary because otherwise occur in addition to the nitration and oxidation )

• Heating 2 - or 4- chloronitrobenzene with alcoholic ammonia
• Sulfonation, nitration and hydrolysis of oxanilide and acetanilide

World production is about 20,000 to 25,000 tons per year.

Properties

The nitro anilines form yellow or orange crystalline powder. They are sparingly soluble in water, soluble in ethanol, ether and chloroform.

PKa values

The nitro anilines have compared to the aniline ( 4.603 ) significantly lower pK a values; the electron-withdrawing nitro ( -M effect) lowers the basicity. A proton can therefore be added considerably worse.

In relative comparison to each other have 2 - and 4 -nitroaniline versus the 3 -nitroaniline a lower pKa value; thus their basicities are smaller. In the ortho -and para- form, a negative charge of the electron-donating amino group ( - I effect and M effect ) through the electron-withdrawing nitro ( -M effect) can be more stabilized. At the meta- form that is not possible, so that the relative electron density on the amino nitrogen is higher, and thus, a proton can be taken up more.

Melting points

The melting points show significant differences. The 2- nitroaniline has the lowest melting point, since it can form an intramolecular hydrogen bond. The other two isomers form, in contrast, from intermolecular hydrogen bonds. 4- nitroaniline having the highest melting point, due to its symmetry.

Use

The nitroanilines can be almost exclusively employed as intermediates for the preparation of other organic compounds. This is how, for example, by hydrogenation of the nitro group and the phenylenediamines by diazotization Nitrobenzonitrile.

4- nitroaniline, for example, the starting point for the synthesis of the azo dye Para Red:

Derivatives

Some derivatives of 3- nitroaniline taste very sweet. 1- propoxy -2-amino -4-nitrobenzene having a sweetening power of 4,100 with respect to sucrose, and has been for some time under the name of P -4000 Ultrasüß used as a sweetener, but toxicological reasons no significance.

Safety

Nitroaniline are poisonous. Upon contact of nitro anilines with organic substances and exposure to moisture can be a spontaneous combustion.