Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF DICHLORONITROBENZENE FROM DICHLOROBENZENE"

Abstract

The invention relates to 'An improved process for the preparation of dichloronitrobensene from dichlorobenzene'. Dichloronitro benzenes are important organic intermediates for the synthesis of quinoline class of antibacterial compounds. The priors art process uses hydrogen fluoride and nitric acid as the nitrating agent. In this process anhydrous hydrogen fluoride for the nitration of dichlorobenzene from either an isomeric mixture of dichlorobenzenes( ortho and para) or from independent 0- or p-isomers. The process is ecofriendly and generates minimum effluents.

Full Text

The present invention relates an improved process for the preparation of dichloronitrobenzene from dichlorobenzene.δ Dichloronitrobenzenes are important organic intermediates for the synthesis of quinoline class of antibacterial compounds. Nitration reaction of benzene or substituted benzene is an electrophilic substation and various processes have been proposed using different nitrating regents known in the art. Conventional method for the preparation of dichloronitrobenzenes from dichlorobenzenes is using nitric acid and sulphuric acid. Preparation of dichloronitrobenzene described in [CN: 1,038, 477(1990)]; [CN: 1,070,904A(1993 )]HuP:31,618( 1984);HauxueFanyingGonchengYuGougyi,[CN: 11,31 0 -14(1995)],YiyaoGougue,[CN:15,269(1987)];J.Chem.Soc.l23,3247(1923;Org.Chem.Ind. 1 342(1936)(USSR); Zhongguo Yiyao Gongye Zahi, [CN:27,33(1996)] from 0- dichlorobenzene and p-dichlorobenzene with sulphuric acid and nitric acid respectively. Nacking drug research department of China [CN:1,075.949A,(1993)] and Zhu, Chonquan. Etal. [Zhongguo Yaowu Huaxue Zazhi[CN:4,285(1994)j claims p- and 0-dichlorobenzenes as a source material and nitration is carried out with mixed acid (H2SO4+HNO3). This traditional technique gives the product in good yield but the disadvantage of the process is a large quantity of mixed acid is to be poured in to ice-water during work-up and the quantity of the spent acid and effluents generated from organic layer washings creates problems for the treatment and its disposal. Later Bayer Company [EP: 5581, 148(19994)] used phosphoricacid along with the mixed acid for the nitration of o-dichlorobenzene and reported 2,3-dichloronitrobenzene as the major product. The attention was focused on the replacement of sulphuric acid of the mixed acid. Anthony G.M.Barrett.etal reported Inflates of Hafnium and Zirconium [Tet.lett.39,1641-1642(1998)] and nitric acid for the nitration of o-nitrotoluene. Dinitration of toluene [EP:251,9539(1988)] claimed by Desbois, Michael using nitric acid and a large excess of hydrogenfluoride. Bruce A.knowalczyk. etal.claimed the usage of trifluoroacetic acid-nitric acid mixture [organic Process Research Development,l,355-358(1998)]and Roy B.Moodie.etal. [J.C.S.Perkin.Trans.2,318-23(1978)] used nitric acid-perchloric acid as the nirtrating agent. Nitronium trifluoro methane sulphonate is used for the nitration of p-dichlorobenzene by Yagupol'Skii.LM. etal. [Zh.Org.Khim.,10,2226-7(1974)]. The usage of inflates of metals, trifluoroacetic acid and perchloric acid as a replacement for sulphuric acid may be attractive but they are quiete expensive, not feasible for commercial production of nitrobenzenes. Solid acid catalysts are the current interest for nitration reactions. German patent [2,510,09591995)] claims ca'ilytic (alumina or silicagel impregnated with phosphoricacid or sulphuricacid) vapour phase reaction of o-dichlorobenzene with nitric acid or nitrogen dioxide or dinitriogen pentoxide or their mixture. Jose M .Zaldivar. etal. Reported [Tet.lett. 37.513-6(1996)] the preparation of 2,5-dichloronitrobenzene from p-dichlorobenzene using nitric acid (70%) and a solid acid catalyst (sulphuric acid on silicagel). Though the usage of solid acid catalysts and catalytic vapor phase reactions leads to less pollution, the reactions require higher temperatures and used mainly for mononitrations. Thus all methods cited above have got disadvantages over the developed process using hydrogen fluoride and nitric acid as the nitrating agent for the preparation of dichloronitrobenzenes. Hydrogen fluoride is an indigenously available chemical and can be used at commercial level also. The novelty of the present invention lies in the use of anhydrous hydrogen fluoride for the nitration of dichlorobenzene to prepare dichloronitrobenzene. The objective o the present invention is to describe a viable process for the preparation of dichloronitrobenzenes from either an isomeric mixture of dichlorobenzene (o+p) or from independent o- or p- isomers. The other objective of the present invention is to provide a suitable substitute from sulphuric acid in the nitration reaction in the form of hydrogen fluoride which is widely accepted chemical. Yet another objective is to minimize the quantities of spent acids generated in the down stream process and the recovery and recycle the excess hydrogen fluoride from the 'eaction is an additional advantage in respect to atom economy. Accordingly, the present invention provides an improved process for the preparation of dichloronitrobenzene from dichlorobenzene which comprises reacting ortho or para dichlorobenzene or a combination of two with nitric acid in a dichlorobenzene to nitric acid ratio ranging from 1:1 to 1:1.5 (w/w) in the presence of an anhydrous hydrogen fluoride with hydrogen fluoride to nitric acid ratio in the range of 1:1 to 5:1 at a temperature ranging in between -10 to +80°C, distilling the excess hydrogen fluoride and diluting the reaction mixture with water and washing the organic layer with alkali such as herein described followed by water, finally drying the product to obtain the desired dichloronitrobenzene. In an another embodiment of the present invention the mole ratio of dichlorobenzene to nitric acid is in the range 1:1 to 1:1.2. In an another embodiment of the present invention the weight ratio of hydrogen fluoride to nitric acid is preferably in the range1:1 to 2:1. In an another embodiment of the present invention the hydrogen fluoride used is recovered by distillation. Details of invention: The present invention relates to anhydrous hydrogen fluoride catalysed nitration of dichlorobenzenes(Scheme-l). A mixture of dichlorobenzenes and hydrogen fluoride is charged in to a cylindrical SS-316 reactor equipped with a stirrer, cooling condenser and with provision for addition of nitric acid. The contents of the reaction mixture were cooled by circulating cold water with an immersed coil in the reactor. Fuming nitric acid in hydrogen fluoride is slowly added with constant stirring maintaining the temperature in the range -10° to +80°C and preferably in the range 0° to 60°C. The mole ratios of dichlorobenzenes to nitric acid are in the range of 1:1 to 1:1.5 and preferably 1:1.3 and more preferably 1:1.1. The weight ratio of hydrogenfluoride to nitric acid is in the range of 1:1 to 5:1 preferably 2:1. After completion of addition of nitricacid the excess hydrogen fluoride was distilled and reaction mixture is diluted with water. The organic layer is thoroughly washed with alkali followed by water, dried and distilled obtaining dichloronitrobenzenes more than 97% yield. The present invention is described with reference to the following examples, which are explained by way of illustration and should not therefore be construed to limit the scope of invention. Example-1: A cylindrical SS-316, 450ml reactor of dimensions 2.5" id, depth 6" with an working capacity of 325ml equipped with a stirrer, thermowell, cooling coil safety rupture disc and a valve connected to condenser and receiver. The reactor is charged with an isomeric mixture (45%& 55%) of o,p-dichlorobenzenes (147g) and hydrogen fluoride (140g). The mixture is cooled to 5°C by circulating cold water into the cooling coil with constant stirring. Fuming nitric acid (70g) is added slowly maintaining the temperature not exceeding 30°C. After completion of the addittion of nitric acid, the reaction mixture is allowed additional 15 minutes at an ambient temperature and the excess hydrogen fluoride is distilled condensed and collected (105g) in an SS vessel cooled to -20°C wit ice-salt mixture. The contents of the reactor are diluted with water. The bottom organic layer is separated and washed successively with alkali solution followed by water till the washings are neutral to pH and the quantity of effluent (150g). The organic layer is distilled at 134-140°C /5mm obtaining a mixture of dichloronitrobenzenes and analysed by GC. The product distribution as 43.88% 3,4-dichloronitrobenzene, 48.21% 2,5-dichloronitrobenzene and 7.9% 2,3- dichloronitrobenzene and yield is 98%. Comparative example: The reaction setup used as described in example-1, but the mixture of hydrogen fluoride (70g) and isomeric mixture of dichlorobenzenes (147g) charged into the reactor and the nitration mixture separately prepared by mixing nitric acid (70g) and hydrogen fluoride (70g)). The nitration mixture is added slowly to the contents of the reactor maintaining the temperature not exceeding 30°C while stirring. After completion of the addition of nitration mixture, it is further stirred at an ambient temperature for 15 minutes and the work up methodology is followed exactly as described in example-1. The yield of dichlronitrobenzenes is 97%. Example-2: The nitration reaction of o-dichlorobenzene (147g) is carried out exactly as in example-1 obtaining 3,4-dichloronitrobenzene 96% and 2,3- dichlronitrobenzene 3.5%. The yield is 98%. Example-3: The nitration reaction of p-dichlorobenzene (147g) is carried out exactly the same way as described in example-1, obtaining 2,4- dichloronitrobenzene 98% analysed by GC. The yield is 99%. Advantages: The main advantage of this new process is the usage of anhydrous hydrogen fluoride in place of conventional sulphuricacid which is an industrial chemical and convenient to recover the excess after completion of the reaction. Other advantage of the process is ecofriendly because of the minimum generation of the effluents. We Claim: 1. An improved process for the preparation of dichloronitrobenzene from dichlorobenzene which comprises reacting ortho or para dichlorobenzene or a combination of two with nitric acid in a dichlorobenzene to nitric acid ratio ranging from 1:1 to 1:1.5 (w/w) in the presence of an anhydrous hydrogen fluoride with hydrogen fluoride to nitric acid ratio in the range of 1:1 to 5:1 at a temperature ranging in between -10 to +80°C, distilling the excess hydrogen fluoride and diluting the reaction mixture with water and washing the organic layer with alkali such as herein described followed by water, finally drying the product to obtain the desired dichloronitrobenzene. 2. A process as claimed in claim 1 wherein in the reaction temperature is preferably in the rage of 10to60°C. 3. A process as claimed in claims 1 & 2 wherein the mole ratio of dichlorobenzene to nitric acid is in the range 1:1 to 1:1.2. 4. A process as claimed in claims 1-3, wherein the weight ratio of hydrogen fluoride to nitric acid is preferably in the range 1:1 to 2:1. 5. A process as claimed in claims 1-4, wherein the hydrogen fluoride used is recovered by distillation. 6. An improved process for the preparation of dichloronitrobenzene from dichlorobenzene substantially as here in described with reference to the examples and drawing accompanying with this specification.

Documents:

478-del-2001-abstract.pdf

478-del-2001-claims.pdf

478-del-2001-correspondence-others.pdf

478-del-2001-correspondence-po.pdf

478-del-2001-description (complete).pdf

478-del-2001-drawings.pdf

478-del-2001-form-1.pdf

478-del-2001-form-18.pdf

478-del-2001-form-2.pdf

478-del-2001-form-3.pdf