IE44134B1 - Process for the preparation of n-phenyl-5-chloro-2-nitroaniline - Google Patents

Abstract

PURPOSE: To obtain a rubber composition excellent in heat resistance, strength characteristics, low abrasion resistance and wear resistance after curing by adding specific two kinds of sliding agents to a partially hydrogenated unsaturated nitrileconjugated diene based copolymer and an unsaturated carboxylic acid metallic salt. CONSTITUTION: The objective composition is obtained by blending (A) a partially hydrogenated unsaturated nitrile-conjugated diene-based copolymer having ?120 iodine value (e.g. uhydrogenated product of butadiene-acrylonitrile copolymer rubber) with (B) an ethylenically unsaturated carboxylic acid metallic salt, (C) a silicone rubber and (D) a fluororesin (preferably a powdery fluororesin), preferably at amounts of 5-100 pts.wt. component B, 1-10 pts.wt. component C and 1-30 pts.wt. component D based on 100 pts.wt. component A. As the component B, a Zn salt, a Mg salt, a Ca salt or an Al salt of an ethylenically unsaturated carboxylic acid such as (meth)acrylic acid or maleic acid is preferably used. Furthermore, an organic peroxide based compound such as dicumyl peroxide is preferably used as a curing agent of the composition[JPS5287125A]

Description

, This invention relates to the preparation of N-phenyl 5-chloro-2-nitroaniline.

N-phenyl-5-chloro-2-nitroaniline of the formula Cl no2 is an important precursor for, and intermediate in, organic chemical syntheses and preparation of pharmaceutical active ingredients.

The preparation of this compound from 3,4-dinitrochloro-benzene and aniline is known (Ber. 2, 771 (1876); J. Chem. Soc. (B), 1968, 623). This reaction proceeds very slowly (over days), the work-up is very complicated and only after repeated recrystailization is a pure product obtained and then only in a low yield. Moreover, the nitrous acid split off reacts with aniline to give by15 products such as aminobenzene and phenol.

When this synthesis is attempted on an industrial scale, there is considerable risk because these inevitable by-reactions, especially at an elevated temperature, may proceed with a sudden development of nitrogen and uncon20 trollable decomposition.

According to Abramovitch and Davis, J. Chem. Soc.

(C), 1968, 119-126, 2,4-dichloronitrobenzene may be reacted with the aromatic amine 2,4-dichloroaniline in the presence of powdered potassium hydroxide in benzene. This reaction leads to a great number of compounds such as 2,2', 4,4'tetrachloroazobenzene, 1,3,6,8-tetrachlorophenazine, 1,4,5'trichloro-2'-nitrodiphenylamine, 2,7-dichloro-phenazine and an unidentified substance.

We have now found surprisingly that the reaction of 2,4-dichloro-nitrobenzene and aniline may lead in a defined reaction to N-phenyl-5-chloro-2-nitroaniline in a yield of over 90%, if the reaction is carried out at higher temperatures, not with alkali, but with aniline in excess or with at least one mol equivalent of aniline in the presence of a tertiary organic base, the boiling point of which is expediently above 100°c.

The present invention provides a process for the preparation of N-phenyl-5-chloro-2-nitroaniline, which comprises reacting 2,4-dichloro-nitrobenzene with aniline, the reaction being carried out with at least one mole equivalent of aniline in the presence of at least one mole equivalent of a tertiary organic amine or with excess aniline (i.e. more than 2 mols of aniline per mole of 2,4dichloronitrobenzene) .

When using only aniline the molar ratio of aniline to 2,4-dichloronitrobenzene is expediently at least 2:1, since one mol of aniline is required for binding the resulting hydrogen chloride. There is no limit on the excess of aniline used, which may simultaneously serve as a solvent.

Instead of the excess of aniline, there may also be used at least one mol equivalent of aniline for the reaction and at least one mol of an organic tertiary base for binding the hydrogen halide. Both aniline and the tertiary organic amine may be used in a larger excess, Tertiary organic amines having a boiling point below 100°C are less suitable for the process of the invention since they are too easily volatile. Preferred amines are, therefore, Ν,Ν-dimethyl- and N,N-di-ethylaniline and aliphatic amines such as, for example, tripropylamine, tributylamine or tri-isopropylamine. Mixtures of the above-mentioned tertiary amines may be used. When using the tertiary organic amines in a larger excess, they may simultaneously serve as solvents.

The reaction may also be carried out in the presence of a different inert solvent having a high boiling point, for example butanol, glycols, polyethylene glycols, aliphatic and aromatic hydrocarbons such as, for example, toluene or xylene. When using such solvents, the excess of aniline and/or of the tertiary organic amine may be reduced.

The reaction is suitably carried out at an elevated temperature, preferably in the range of from 100 to 18O°C. When using only aniline, it is expedient to work without pressure; when using additional tertiary organic amines or solvents having a lower boiling point than aniline, the reaction is expediently carried out in a closed system depending on the boiling point. When using other solvents or tertiary organic amines under normal pressure, the reaction time has usually to be prolonged according to the reflux temperature.

As compared with the method of preparation hitherto known for N-phenyl-4-chloro-2-nitroaniline, the process of the present invention has the great advantage that the - 5 reaction generally proceeds as desired in a few hours and with a high yield. This also gives a more economical preparation of the substance. Furthermore, this process may be transferred without any substantial risks to the industrial scale.

The following Examples illustrate the invention.

EXAMPLE 1 A mixture of 372 g (4 mols) of aniline and 192 g (1 mol) of 2,4-dichloronitrobenzene was heated over one hour to 160°C and maintained at this temperature for 7 hours. After cooling to about 80°C, the reaction mixture was poured into 750 ml of methanol.

At O°C the crystallized substance was suctionfiltered, washed with methanol and dried in vacuo at 50°C. The yield was 225 g, corresponding to 90.5% of the theoretical amount.

The melting point was 108°C.

EXAMPLE 2 A mixture of 93.1 g (1 mol) of aniline, 363.6 g (3 mols) of Ν,Ν-dimethylaniline and 192 g (1 mol) of 2,4dichloronitrobenzene was heated over one hour to 160°C and maintained at this temperature for seven hours.

The mixture was subsequently subjected to a water-steam distillation. The residue obtained was separated from water and mixed with 600 ml of methanol.

After stirring for half an hour and cooling to O°C, the N-phenyl-5-chloro-2-nitroaniline was isolated as described under Example 1.

Claims (11)

1. CLAIMS:1. A process for the preparation of N-phenyl-5-chloro2-nitroaniline, which comprises reacting 2,4-dichloro-nitrobenzene with aniline, the reaction being carried out with at least one mole equivalent of aniline in the presence of at least one mole equivalent of a tertiary organic amine or with excess aniline (as hereinbefore defined).

2. A process as claimed in claim 1, wherein the molar ratio of aniline to 2,4-dichloronitrobenzene is at least 2:1.

3. A process as claimed in claim 2, wherein the molar ratio of aniline to 2,4-diehlorOnitrobenzene is at least 4:1.

4. A process as claimed in any one of claims 1 to 3, wherein the tertiary organic amine has a boiling point of at least 1OO°C.

5. A process as claimed in claim 4, wherein the amine is N,N-dimethylaniline, Ν,Ν-diethylaniline, tripropylamine, tributylamine or tri-isopropylamine.

6. A process as claimed in any one of claims 1 to 5, wherein the reaction is carried out at a temperature of at least 100°C.

7. A process as claimed in claim 6, wherein the reaction is carried out at a temperature in the range of from 100 to 180°C.

8. A process as claimed in any one of claims 1 to 7, wherein the reaction is carried out in an inert solvent.

9. A process as claimed in claim 8, wherein the solvent is butanol, a glycol, a polyethylene glycol, or an aliphatic or aromatic hydrocarbon.

10. A process as claimed in claim 1, carried out substantially as described in Example 1 or Example 2 herein.

11. N-phenyl-5-chloro-2-nitroaniline, whenever prepared by a process as claimed in any one of claims 1 to 10.