DE138496C - - Google Patents

Description

^ PATENT LETTERING

CLASS 12 q.

Patent in the German Empire from! 4. August 1900 onwards.

Except for the long-known and technical ones useful methods for reducing nitro and allied bodies by means of iron or tin in acidic solution and zinc dust in alkaline solution became different in various ways Taken paths.

So tried v. Dechend nitro body through To reduce zinc (with or without iron) in the presence of aqueous salt solutions (Patent 43240 extinguished). Furthermore Wohl operated (reports of the former German society 1894, P. 1432) with zinc or iron in neutral solution and in this way obtained ir.it zinc in the presence of neutral salts hydroxylamine derivatives (patent 84138) with iron in neutral Solution also of aniline in small quantities, but these methods were just as little accepted in technology, as the reaction in an alkaline solution by means of finely divided lead Obtaining azo bodies (Wohl, Patent 81129 extinguished); partly because the yields were unsatisfactory, partly because the procedures were too expensive. The only really cheap reducing agent available is iron.

It has now been found that iron and alkali are excellent reducing agents form. When it is applied to nitrobenzene, for example, the following are formed: azoxybenzene, azobenzolj Hydrazobenzene, and aniline permits the present process to use any one of these compounds to be shown separately respectively. z. B. azoxybenzene or azobenzene. Hydrazobenzene to reduce and so on.

When using, for example. The reduction process takes place in the form of soda as alkali so that the nitro body produces the desired product of reduction, depending on the duration and nature of the reduction gives, while that of the reduction product separate sludge when diluted with water in iron oxide respectively. Iron oxide hydrate and caustic soda break down. the Caustic soda is successfully used for new reductions after concentrating.

As a further considerable technical effect, compared to the reduction process by means of zinc dust and alkali, it should be emphasized that the expensive zinc dust is replaced by cheap iron, of which, due to its lower molecular _{weight and its ability to oxidize to Fe 2} O ₃ , much less is required for reduction as of zinc dust, which can only oxidize to Zn O.

For example, to produce hydrazobenzene from 1000 kg of nitrobenzene, only 900 to 1000 kg of iron is used instead of 1600 kg of iron zinc dust about ten times as expensive. Furthermore, in the present method the alkali to be used can be recovered, while the same can be done with the alkaline zinc reduction not only lost is, but still requires appropriate amounts of acid for neutralization.

Instead of having the nitro body etc. for yourself They can also be subjected to reduction in the presence of water mixed with solvents, hydrocarbons or alcohols, reduce. It is this Particularly recommended for bodies> whose hydrazo compounds have a high freezing point to have.

Examples: · Example I.

Reduction of a nitro body to the corresponding azoxy compound: 12001 of a sufficiently high-boiling hydrocarbon, 600 kg of o-nitrotoluene and 1800 kg of iron are poured into a stirrer, Heizr and the apparatus provided with a cooling device brought and warmed to ι io °. Then the little by little 5001 caustic soda from about 6o ° B. added and the temperature kept at 110 to i2o °. If the characteristic When the smell of the nitro body has disappeared, the solution of azoxytoluene is drained off and the hydrocarbon is distilled off. With the hydrocarbon, some of the toluidine formed at the same time passes over, which passes through You can be withdrawn from it. The remaining azoxytoluene can be used for cleaning, e.g. B. from alcohol, be recrystallized.

Example H.

Reduction of a nitro body to the corresponding azo compound:

In a described above boiler 40 kg of iron, 100 1 hydrocarbon and 5kg of o-nitroanisole heated to 90 °, then 6 kg of sodium hydroxide solution of 50 ⁰ B. be added and the temperature maintained as long as between 90 and iio ° until the Formation of the azo body is accomplished. The solution of o-azoanisole is then drained off, some of the hydrazoanisole formed by the side is removed from it by shaking with acid, and the hydrocarbon is distilled off. The body can be kept completely pure by recrystallization.

Example IH.

Reduction of a nitro body to the corresponding amide compound: 100 kg of p-nitracetanilide, dissolved in 500 1 of hydrocarbon, are poured into a boiler equipped as above, then 250 kg of iron and 200 kg of sodium hydroxide solution 50 ⁰ B. are added, the mixture is heated to 130 ° and kept at this temperature until the reduction is complete. Almost all of the p-phenylenediamine crystallizes out of the withdrawn solution on cooling; the mother liquor can be used for new reductions.

Example IV.

Reduction of a Azokörpers to the corresponding amido compound: 'In the repeated-mentioned apparatus 200 kg amidoazobenzene dissolved in 1000 1 hydrocarbon to be "charged 250 kg of iron and 200 kg of sodium hydroxide of 50 ⁰ B., heating the mixture to 130 ⁰ and after the completion of reduction the solution is drained off, the amount of p-phenylenediamine formed crystallizes out, and the remainder of the mother liquor and the aniline formed in the process are recovered from the mother liquor.

. ■; Example V.

Gradual reduction

a nitro body for azoxy or.

to azo, hydrazo or amido

link:

a) 100 kg of nitrobenzene and 750 kg of iron are placed in an apparatus equipped with a stirrer, heating and cooling device and warmed to about 90 °, then 800 kg of sodium hydroxide solution at 55 ° are gradually added; the temperature is kept at 100 to 120 ⁰ and BEZW by steam. Regulated cooling water. In addition to the change in color, the disappearance of the characteristic odor of the nitro body, etc., a good indicator of the course of the reduction is the freezing point, which changes significantly depending on the phase reached. The freezing point, which in technical nitrobenzene is around + 5 °, drops significantly (in this example to around - 13 ° and around 40 pCt. Of the nitro body is then converted into azoxybenzene). The freezing point then begins to rise again, in this example up to 31 °. When this point is reached and the smell of nitrobenzene has disappeared, the azoxybenzene formed is drained off.

b) If azobenzene is to be obtained instead of azoxybenzene, the azoxybenzene can be reduced to azo compound by further heating and adding 250 kg of iron and 300 kg of sodium hydroxide solution. The solidification point of the mass reduction is lowered to about 25 ⁰ first and then rises to about 63 °. The apparatus can then be stopped and the azobenzene drained.

c) If the reaction is to be carried out until hydrazobenzene is prepared, the azobenzene obtained, or an amount of the same amount corresponding to the amounts of nitrobenzene used above, can be reduced to hydrazo compound by adding 250 kg of iron and 300 kg of sodium hydroxide solution, and this first fills the solidification point up to about 55 ⁰ and then rises to 122 to 125 °. This has reached the desired phase and the hydrazobenzene can be drained off.

One liffst the temperature at the conclusion zweckma'fsig to 130 ⁰ to rise, so that the mass does not solidify in the apparatus, or mail lowers the freezing point by adding a solvent. ^;

d) Should the reduction be carried out to aniline 250 kg of iron are added to the hydrazobenzene obtained above and 300 kg of sodium hydroxide solution and continued to heat.

BPV'i'Tr> Μ ^ ί. W; V-s

The aniline formed can be obtained by distillation.

You can bezw the ratios between soda, iron, water and nitro bodies. Azoxy, Azo and hydrazo bodies and the way in which the various substances are brought together also choose different from what is specified in the examples, as well as the temperature.

Claims (1)

Patent claim: Process for the reduction of nitro, azoxy, azo and hydiazo compounds of the benzene series, characterized in that these compounds are possibly in the presence of a organic solvent heated with iron and aqueous alkali.