FORM 2
The Patent Act 1970,
(39 of 1970)
&
The Patent rule 2003
Provisional Specification
(See Section 10 and Rule 13)
1. TITLE OF THE INVENTION
Process for preparation of 5-chloro-1,3-phenylenediamine

3. PREAMBLE TO THE DESCRIPTION
The following specification describes the invention


PROCESS FOR PREPARATION OF 5-CHLORO-1.3-PHENYLENEDIAMINE
FIELD OF INVENTION
The invention relates to a process for preparation of 5-chloro-1,3-phenylenediamine (I) with better yield and purity from isophthalic acid and other non hazardous raw materials through the intermediate, 5-chloro-N,N'-dichloroisophtha!arnide. 5-Chloro-1,3-phenylenediamine (I) is used in preparation of aromatic polyamides and as well as an intermediate in the fine chemicals industry.
In still further details the present invention involves the chlorination of isophthalic acid to isophthaloyl chloride, its conversion to the amide, and the two step conversion of the amide to the amine by Hoffman degradation via the intermediate 5-chloro-N,N'-dichloroisophthalamide.
BACKGROUND OF INVENTION
German Patent DE108165 describes a method for the production of 5-chloro-1,3-phenylenediamine (I) which involves the chlorination of m-dinitrobenzene at 100°C and using a chlorine carrier such as iron chloride, antimony chloride etc. and reduction of the dinitro compound to the diamine.

In an another reference in The Journal of the Chemical Society' M. Melhuish et. al. in, PerkinTransactions 2:Physical Organic Chemistry (1972-1999)(1989),(6),667-73 reports the chlorination of m-dinitrobenzene at 130°C in a mixture of sulfuric acid and oleum to get the chlorinated dinitro compound which is then reduced to the diamine.
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J.Am.Chem.Soc., 63, 3276(1941) describes a method of preparation of (I) wherein 3,5-dinitrochlorobenzene is prepared from 3,5-dinitroaniline by the Sandmeyer reaction. After purification by column chromatography, the nitro compound was hydrogenated over SnCI2/HCI to form (I).
JP 53121725 describes a method for preparation of (I) by copper catalysed ammonolysis of 1,3,5 trichlorobenzene in aqueous ammonia and triethyl amine solutions at 200°C. However various isomer mixtures are obtained.
However these are hazardous methods involving the chlorination under severe conditions of dinitro compounds at high temperatures in sulfuric acid/oleum to get the chlorodinitro benzenes, which have then to be separated from isomers to get pure dinitro compound and then reduced. Or else by conversion to chlorodinitro compound by the Sandmeyer reaction of dinitro aniline and subsequent reduction.
But none of the above methods addressed the preparation of 5-chloro-1,3-phenylenediamine (I) in a simple method with high yield and purity without the use of hazardous chemicals and conditions. Accordingly the present invention tries to find out the method for preparation of the said compound to overcome the prior art defects.
OBJECT OF INVENTION
In these respects, hence it is desired to overcome the disadvantages of the past methods of preparation by developing a process, which uses safe raw materials and also gives product of high purity in high yield.
One object of the present invention is to provide a new and improved process for the production of (I) starting from Isophthalic acid, whereby higher yields and a pure diamine are more readily assured.
Another object of the present invention is to carry out the preparation of (I) by starting from
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Isophthalic acid in four distinctive, separate and therefore more easily controlled stages, with isolation or separation of an intermediate product from a first stage before carrying out the second stage, it is also an object to provide a more economical and a much simpler recovery of the final pure product.
A still further object of the present invention is to provide a process, which uses safer raw materials and hence is less hazardous in nature. These and other advantages of the present invention will become more apparent upon consideration of the following detailed description.
STATEMENT OF THE INVENTION
Process for preparation of 5-chloro-1,3-phenylenediamine (I) comprises of the following steps:
(a) Preparation of isophthaloyl chloride by reaction of isophthalic acid and thionyl chloride at a predetermined temperature for a certain duration;
(b) Chlohnation of isophthaloyl chloride to the 5-chloroisophthaloyl chloride using chlorine and a chlorine carrier such as iron chloride at high temperatures for a certain duration in such a manner so that further chlorination resulting in increase of dichloroisophthaloyl chloride can be interrupted;
(c) Fractional Distillation of the chlorinated mass using a packed column as herein described to obtain 5-chloroisophthaloyl chloride of high purity;
(d) Conversion of 5-chloroisophthaloyl chloride to the corresponding diamide at ambient temperature by addition to aqueous ammonia;
(e) Conversion of diamide to the 5-chloro-N,N'-dichloroisophthalamide by chlorination in aqueous media and in the presence of an antifoaming agent with the stoichiometric amount of chlorine passed over a period of certain hours at a definite temperature range till no more weight gain is observed; and
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(f) Conversion of 5-chloro-N,N'-dichloroisophthalamide to 5-chloro-1,3-
phenylenediamine (I) at a temperature range of 0°C to 120°C for a certain period after addition to an aqueous NaOH solution and then heating the whole mass to the desired temperature for completion of the reaction and then cooling and extracting with a suitable solvent followed by crystallization to obtain the desired crystalline product.
DESCRIPTION OF THE INVENTION




(d)


(e)




(f)

According to the process of this invention the isophthaloyl chloride is chlorinated to the 5-chloroisophthaloyl dichloride using chlorine and a chlorine carrier such as iron chloride at a high temperature. The temperature may be in the range of 100-200°C and more preferably in the range of 120°C-180°C.
According to the process of this invention the chlorination is interrupted when the maximum amount of 5-chloroisophthaloyl dichloride is obtained and when further chlorination results In increase of dichloroisophthaloyl chloride.
According to the process of this invention the reaction mass is then fractionated using a 20 stage fractionating column, which separates the pure 5-chlorisophthaloyl chloride.
The 5-chlorisophthaloyl chloride is converted to the amide at temperature between 0°C to 50°C by addition to aqueous ammonia and the solids filtered and dried. The melting point of the amide is 263°C-264°C.
The amide is converted to the N,N'-dichloroisophthalamide by chlorination in aqueous media in the presence of an antifoaming agent by the method described by S. S. Mathur according to IN161317. Stoichiometric amount of chlorine was passed over a period of 8-24 hours at a temperature of 10°C to 50°C. When no more weight gain is observed, the reaction was filtered and washed till acid free to obtain the wet cake of N,N'-dichloroisophthalamide.
According to the process of this invention 5-chloro-N,N'-dichloroisophthalamide was converted to (I) by Hoffman degradation. The process of this invention may be carried out in a temperature range of 0°C to 120°C and more particularly at a temperature range of 10°C to 80°C. To an aqueous NaOH solution, 5-chloro-N,N'-dichloroisophthalamide was added and the whole mass heated to the desired temperature. The reaction is maintained at this temperature for 1-5 hours and cooled. The reaction mass is extracted with a suitable solvent and recrystallised to obtain crystalline solids (yield 75-85%) of purity greater than 99%.
The invention is illustrated with the following example without limitation to the scope of invention.
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EXAMPLES
Example 1 :
Thionyl chloride (40 moles) is charged with isophthalic acid (8 mole) and heated to 60°C and maintained for 3 hours to obtain clear solution. The excess thionyl chloride is distilled off. FeCI3 (3 mole%) is added and chlorine gas is passed for 12 hours at 170°C. The reaction mass analysis shows conversion to 5-chloroisophthaloyl dichloride (66%), with the remaining amount of unreacted isophthaloyl chloride, (25%) and the dichlorinated product (10%). 1280 gms of this material is fractionated using a glass column (height 3' and diameter 1") packed with glass helices having 20 theoretical plates. The pressure is 1-2 mm Hg. The Distillation data is given below:

Cut No. Vapour
Temp.
°C Weight gm Isophthaloyl
chloride
% 5-Chloroisophthaloyl dichloride
% Dichlorinated
product
%
1 85-88 456 22.4 77.2 -
2 88-90 206 79.6 20.1 0.1
3 90 151 1.94 97.6 0.22
4 91 135 0.4 99 0.4
5 91 130 0.04 99.5 0.4
6 91 70 - 100 -
Cut No. 3-6 was mixed to give composite GC analysis of 99% purity.
Example 2 :
426 g of 5-Chloroisophthaloyl dichloride was added to 3.5 L of aqueous ammonia (9.7N) and the precipitated solids were filtered and dried to obtain 345 g of desired product corresponding to 96% yield with a melting point of 264°C.
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Example 3 :
345 g of 5-Chloroisophthalamide was taken in water (2 L/mole) and 0.5 gm of antifoaming agent was added and chlorine was passed at a rate of 0.35 moles/hour over a period of 10 hours. The reaction mass became thick and almost unsti'rrable. Hence added extra water (1.5 Lit/mole) and continued chlorine passing for another 5 hours. The reaction mass was filtered and washed to remove acidity. The wet cake obtained was 1265 gms.
Example 4 :
421 gms of the wet cake obtained in Example 3 was added under N2 over a period of 15 minutes to a chilled solution of 142.6 gm NaOH dissolved in 1340 gm water. The reaction mass was maintained for half an hour till clear solution was obtained. The reaction mass was further heated to 80°C over a period of 3 hours and maintained at this temperature for 1 hour and then cooled. The reaction mass was extracted with ethylene dichloride (2 x 300 ml): The combined ethylene dichloride extract on concentration gave crystalline white solids (melting point 103°C), which on recrystallisation gave (I), 60 gms, purity (99.5 %) with yield (73. 5%) and melting point (105°C).
Different embodiments of the invention are possible to achieve the best method of performance and to obtain the effective and better product as stated earlier. It will be understood that skilled persons with many modifications, variations and adaptations may carry out the invention into practice without departing from its spirit or exceeding the scope of claims in describing the invention for the purpose of illustration.
Dated this 28th day of July 2008

Satish B. Limaye' Sr. Officer- Sci. Inf. & IPR Management. Gharda Chemicals Ltd.