CS260448B1 - Process for preparing 4-iodoaniline - Google Patents

Abstract

The method of preparing 4-iodoaniline by reacting aniline with iodine in an alkaline medium proceeds in such a way that the crude 4-iodoaniline, after being separated from the aqueous medium, is purified by crystallization from a solution in an aliphatic hydrocarbon with six to eleven carbon atoms and with a normal and/or branched chain or from a mixture thereof with olefins and non-aromatics, as contained in the raffinate. 1 to 10 vol. % of indane or another substance that dissolves 4- -iodoaniline well is added to the solution of 4- iodoaniline in the hydrocarbon or in the raffinate.

Description

The invention relates to a process for the preparation of 4-iodoaniline.

The method of preparing 4-iodoaniline from aniline by the action of iodine is described in the literature. The disadvantage of this isolation method is the exclusion of the product in insufficient purity, often in oily form. To obtain a pure product, several repeated crystallizations are necessary.

The above-mentioned shortcomings are eliminated by the method of preparing 4-iodoaniline by reacting aniline with iodine in an alkaline medium, according to the invention. Its essence lies in the fact that the crude 4-iodoaniline, after being separated from the aqueous medium, is purified by crystallization from a solution in an aliphatic hydrocarbon with six to eleven carbon atoms and with a normal and/or branched chain or from a mixture thereof with olefins and non-aromatics as contained in the raffinate. It is further possible that 1 to 10 vol. % of indane or another substance that dissolves 4-iodoaniline well is added to the solution of 4-iodoaniline in wt. % of the hydrocarbon or in the raffinate.

The advantages of the process according to the invention lie in the separation of the product in sufficient purity and in the speed and simplicity of carrying out the process.

The invention and its effects are explained in more detail in the description of 2 examples of carrying out the process for preparing 4-iodoaniline according to the invention.

According to the invention, it has now been found that one or two crystallizations from aliphatic hydrocarbons, for example n-hexane, or from a raffinate, which is a mixture of aliphatic hydrocarbons, both normal (approx. 22%) and branched (approx. 85%), with an admixture of olefins (approx. 1.5 to 2.5%) and non-aromatics (approx. 1%), are sufficient to obtain a pure product. The raffinate is the residue after extraction of aromatics. The composition of the raffinate is as follows:

mol. %

2-methylhexane 0.099 2,3-dimethylpentane 0.099 3-methylhexane 0.198 trans-1,3-DMCP 0.099 n-heptane 7.34 cis-1,2-DMCP 1.19 methylcyclohexane 0.39 2,5-dimethylhexane 2.38 2,4-dimethylhexane 4.96 1,2,4-TMPC 0.20 olefins 1.78 3,3-dimethylhexane 0.099 toluene 0.099 1,2,3-TMCP 0.39 2,3,3-TMCP 0.19 2,3-dimethylhexane 3.97 2-methylheptane 10.81 4-methylpentane 5.75 3,4-dimethylhexane 1.88 3-methylheptane 18.25 n-octane 12.40 dimethylcyclohexane 8.32 ethylbenzene 0.099 isononane 14.28 p-xylene 0.099 o-xylene 0.099 n-nonane 1.98 isodecane 1.88 n-propylbenzene 0.099 m+p-ethyltoluene 0.099 1,2,4-TMB 0.099 n-decane 0.099 iso-Cn 0.198 average molecular weight total n-paraffins 21.8254 iso-paraffins 64,881 olefins 1.78571 non-aromatic 10.8135 C5 2.08333 Ce 8.73016 aromatics 0.694444

0.11

0.11

0.23

0.12

8.42

1.39 0.46

2.39

4.99 0.20 1.83 0.10 0.12 0.40 0.20

3.99 10.88

5.79

1.89

18.37

12.48

8.53

0.11

12.80

0.11

0.11

1.78

1.52

0.095

0.095

0.095

0.080

0.146

114,957

22.7616

63,353

1.82946

11.3252

2.32312

9.00211

0.73073

WITH

It was further found that the addition of some compounds that dissolve p-iodoaniline well increases the yield of crystallization, such as indane. In a mixture with raffinate or gasoline in an amount of 1 to 10 vol. %, it positively affects crystallization. Crude p-iodoaniline is dissolved in the hot state in the said solvent, optionally with the addition of an adsorbent, for example carborafine, bentonite, etc., and after cooling, 4-iodoaniline precipitates in crystalline form.

Example 1

220 parts by weight, i.e. 2.36 moles of aniline, 300 parts by weight, i.e. 3.6 moles of sodium bicarbonate and 2,000 parts by weight of water were introduced into the reaction vessel and the mixture was cooled to 12 to 15 °C, optionally by adding iodine to the reaction mixture. 500 parts by weight, i.e. 1.96 moles of finely ground iodine were added with intensive stirring. The iodine was added gradually at intervals of 2 to 3 minutes so that all the iodine was added within 30 minutes. After all the iodine had been added, the mixture was stirred for another 1 hour. After this time, the reaction was complete and the color of the free iodine practically disappeared. The crude 4-iodoaniline, which separated as a crystalline slurry, was filtered off with suction and dried. The filtrate was saved for the regeneration of iodine. Yield of crude product 432 parts by weight.

For the purification of 4-iodoaniline, the crude product was introduced into a reaction vessel with 2,000 parts by weight of raffinate. The contents were heated under reflux to 75 to 80 °C. After stirring the solution with bleach for 30 minutes, saturation occurred. The solution was transferred, optionally after filtration, with stirring into a reaction vessel cooled under laboratory conditions with ice and salt. 4-iodoaniline crystallized in colorless needles. The undissolved portion from the first crystallization was subjected to the 2nd or 3rd extraction. In batch extraction, the first portion of 4-iodoaniline is colorless, for the second and third extractions it is appropriate to use the addition of carborafine or bentonite. Crystallization yield: 70%. Example 1 and 2

The procedure for preparing crude 4-iodoaniline was the same as in Example 1. Crystallization was carried out from 2,000 parts by weight of technical gasoline to which 3% indane was added. The further procedure was the same as in Example 1. Crystallization yield: 75%.

The method for preparing 4-iodoaniline according to the invention is useful in the chemical industry.

Claims (2)

pRedmEt v A process for the preparation of 4-iodaniline by reacting aniline with iodine in an alkaline medium, characterized in that the crude 4-iodaniline after elimination from the aqueous medium is purified by crystallization from a solution of an aliphatic hydrocarbon having six to eleven carbon atoms and normal and / or branched chain or The invention is based on a mixture thereof with olefins and non-aromatics as contained in the raffinate. 2. A process according to claim 1, wherein from 1 to 10% by volume of indane or other substance that dissolves the 4-iodaniline is added to the solution of 4-iodaniline in the hydrocarbon or raffinate.