Title of Invention

AN IMPROVED PROCESS FOR THE SULFONATION OF AROMATIC COMPUNDS USING SULFURIC ACID UNDER SONICATION

Abstract The present invention relates to improved process for selective and rapid sulfonation of aromatic compounds using sulfuric acid as sulfonating agent and ultrasound as promoter having frequency range between 20-100 KHz.
Full Text FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
( Section 10 and rule 13 )
1. "AN IMPROVED PROCESS FOR THE SULFONATION OF AROMATIC COMPUNDS
USING SULFURIC ACID UNDER SONICATION"
2. (a) Bhanage Bhalchandra Mahadeo
(b) Department of Chemistry,
Institute of Chemical Technology,

University of Mumbai,
Nathalal Parekh Marg., Matunga.

Mumbai 400019, Maharashtra, India.
(c) INDIAN.
The following specification particularly describes the invention and the manner in which it is to be performed.


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AN IMPROVED PROCESS FOR THE SULFONATION OF AROMATIC COMPUNDS USING SULFURIC ACID UNDER SONICATION
ABSTRACT:
The present invention relates to an improved process for the sulfonation of aromatic compounds using sulfuric acid under sonication. The reaction takes place at ambient condition under sonication providing significant enhancement in the reaction rate compared to similar reaction performed under silent conditions. The process was applied to a wide range of aromatic compounds having different steric and electronic properties providing good to excellent yields of the desired products.
FIELD OF INVENTION:
The present invention relates to an improved process for selective sulfonation of aromatic compounds, which comprises reacting aromatic compounds with sulfuric acid in the presence of ultrasound. This is a novel high yielding process for preparing such aromatic sulfonated compounds using ultrasound. The reaction takes place at ambient condition and requires shorter time under sonication. The cavitational effects generated due to ultrasound plays an important role of enhancing the interaction between the sulfuric acid and aromatic compounds thereby enhancing the reaction yield. The process was applied to wide range of aromatic compounds having different steric and electronic properties providing good to excellent yields of the desired products.
BACKGROUND OF INVENTION:
Sulfonation of aromatic compounds is one of the most widely studied reaction and find extensive applications in various organic transformations, "Sulfonation and Related Reactions" by Gilbert E. E, (1965) published by Wiley NY, J. Org. Chem. USSR (1987) by Khelevin R. N..
Several processes have been reported in the literature for sulfonation of aromatic compounds. Cerfontain, H etal., reported the sulfonation of aromatic compounds using Cone. H2S04as the sulfonating agent [J. Chem. Soc. Perkin Trans. II, 1985], Synthesis of

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sodium toluene-p-sulphonate from toluene and sulfuric acid is also reported [Textbook of Organic Chemistry Fourth Edition by Vogel]. Many alkyl aryl sulphonates preparation have been described in WO 2005/042448. Sulfonation of aromatic compounds is described in WO 2006/137473. Sulfonations of Grignard and lithium reagents have been described in J. Org. Chem. 1996, 61, 1530. Sulfonation of aromatic compounds with sulfur trioxide in dichloromethane is reported by Corby, B.W. [J. Chem. Res. Synop. in 2002].
Several other processes are known in the literature utilizing sodium sulfite [J. Org. Chem. 1995, 60, 6563], sulfur trioxide [Synthesis, 1998, 1593] as sulfonating agents etc. However inspite of their potential utility in many cases applications are limited due to lower yield, longer reaction time, and requirement of high temperature. Thus there is a need to provide an economical process for the sulfonation of wide range of aromatic compounds in high yield at ambient conditions, which obviates the drawbacks as detailed above.
In recent years the use of ultrasound in various organic transformation is well known as it enhance the rate, yield and selectivity of reactions "Synthetic Organic Sonochemistry" by J.L. Luchein 1998 published by Plenum press, New York. It can also facilitate reactions at ambient conditions, which otherwise requires drastic conditions such as temperature, pressure or concentrations.
As described above an excellent and speedy process for preparing aromatic sulfonated compounds by ultrasound has been unknown so far, and further improvement has been desired.
It is an objective of this invention to provide a process for preparing aromatic sulfonated compounds at a shorter reaction time using ultrasound. A further objective of the invention is to provide a process, which avoids the disadvantage of the prior art.
SUMMARY OF THE INVENTION:
One aspect of the present invention relates to regioselective sulfonation of aromatic compounds under milder operating conditions using ultrasound as the promoter. Second aspect of the present invention is to provide a process for sulfonation of aromatic compounds giving significant rate enhancement under sonication. Yet another objective of

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the present invention is to provide a process for sulfonation of wide range of aromatic compounds such as toluene, benzene, naphthalene, anisole, o-xylene, m-xylene, p-xylene, chlorobenzene etc.
The present invention provides a process for the sulfonation of aromatic compounds using sulfuric acid as the sulfonating agent under sonication. The subject method provides improvement in many features and are as follows
The present invention provides regioselective sulfonation of aromatic compounds under sonication.
The present invention shows a significant enhancement in the reaction rate for sulfonation of aromatic compounds under sonication as compared to similar reaction performed under silent conditions.
The process was applied to wide range of aromatic compounds having different steric and electronic properties providing good to excellent yields of the desired products. The sulfonation of aromatic compounds takes place at ambient conditions under sonication without any additive.
According to present invention, it becomes possible to carry out regioselective sulfonation of aromatic compounds at a low cost without necessity to invest a large sum of money in plant and equipment.
DETAIL DESCRIPTION OF THE INVENTION:
One aspect of the present invention relates to regioselective sulfonation of aromatic compounds under milder operating conditions using ultrasound as the promoter. Second aspect of the present invention is to provide a process for sulfonation of aromatic compounds giving significant rate enhancement under sonication. Yet another objective of the present invention is to provide a process for sulfonation of wide range of aromatic compounds such as toluene, benzene, naphthalene, anisole, o-xylene, m-xylene, p-xylene, chlorobenzene etc.
The aromatic compounds useful in the practice of the present invention are those having molecular formula Ar-X, wherein Ar is a substituted / unsubstituted aromatic compound and X is individually monovalent substituents, which may be same or different. Typical of such radicals are alky groups such as methyl, ethyl, propyl,

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isopropyl, butyl, decyl, and the like; aryl groups, such as phenyl, naphthyl, and the like; aralkyl groups, such as benzyl, phenethyl and the like; alkaryl groups, such as tolyl, dimethylphenyl and the like; alkoxy groups, such as methoxy, ethoxy, and like; haloalkyl groups, such as chloromethyl, trifluoromethyl, and like; and haloaryl groups, such as chlorophenyl, bromophenyl etc..
The quantity ratio between the aromatic compounds and the sulfuric acid varies depending upon the type of the substituents. Obviously the amount of sulfuric acid employed need only be sufficient to produce the amount of sulfonated aromatic compounds desired.
The reaction can be conducted over a wide range of temperatures and pressure. For convenience the reaction is conducted at atmospheric pressure. The reaction temperature is not lower than the melting point of the substrates and not higher than the boiling point thereof. Since the reaction is exothermic and also the cavitation of ultrasound is effected at higher temperatures. It is desirable not to allow the reaction medium to reach a temperature, which would cause excessive loss of reactants by evaporation or effect the cavitation created by ultrasound.. When the reaction is carried out at a temperature in the vicinity of room temperature any trouble is not brought about. Accordingly the reaction is preferable in the range of 10 to 50 °C, more particularly 30 to 40 °C.
The process of the instant invention is unique, since in the absence of ultrasound the extent of interaction between the aromatic compounds and sulfuric acid may be so slight that no physical evidence of reaction is apparent within the expected time. While in the presence of ultrasound the sulfonation of aromatic compounds is generally completed within a matter of few hours. The probable reason may be that the well known cavitational effect generated due to ultrasound playing an important role of enhancing the interaction between the aromatic compound and sulfuric acid thereby forming the corresponding sulfonated compounds at a faster rate than those observed without ultrasound
No process in hitherto known for sulfonation of aromatic compounds using ultrasound as the promoter in which there is a dramatic increase in the rate of reaction system. The process of the present invention is further described with reference to the

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following examples which are illustrative only and should not be construed to limit the scope of the present invention.
EXAMPLE 1
In a typical reaction, toluene (0.1 mole) and Cone. H2SO4 (0.12mole) under solvent free condition was sonicated at room temperature (25°C) in a clean ultrasonic bath. The ultrasonic bath used in the reaction had a frequency of 33 KHz and electric power rating of 100 W. The reaction was carried out in a 100 ml capacity round bottom flask with a mechanical agitator, and the flask was suspended at centre of ultrasonic bath having the area of maximum cavitations, which was checked using ultrasonic probe. The progress of the reaction was monitored using HPLC analysis. After the completion of reaction, the organic layer was separated. The analysis of the reaction showed a 76% conversion and 100% selectivity towards para toluene sulfonic acid in 45 min. under sonication. In comparison the reaction carried out under silent condition takes place 24 h for completion. Conversion of this reaction was found to be 70% and selectivity toward para toluene sulfonic acid of 90%.
EXAMPLE 2
The charge similar to that of given in example 1 was taken except that anisole was used instead of toluene. The reaction was completed in 45 min. Conversion of the reaction was found to be 80% under sonication. In comparison the reaction was carried out under silent condition (other charge is same as above) took 5 h for completion the completion of reaction was found to be 60% toward 4-methoxy-benzene sulfonic acid.
EXAMPLE 3
The charge similar to that of given in example 1 was taken except that benzene was used instead of toluene. The reaction was completed in 45 min. Conversion of the reaction was found to be 28% under sonication. In comparison the reaction was carried out under silent condition (other charge is same as above) took 5 h for completion the completion of reaction was found to be 13% toward benzene sulfonic acid.

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EXAMPLE. 4
The charge similar to that of given in example 1 was taken except that naphthalene was used instead of toluene. The reaction was completed in 45 min. Conversion of the reaction was found to be 66% under sonication. In comparison the reaction was carried out under silent condition (other charge is same as above) took 5 h for completion the completion of reaction was found to be 11 % toward naphthlene-2-sulfonic acid.
EXAMPLE 5
The charge similar to that of given in example 1 was taken except that o-xylene used instead of toluene. The reaction was completed in 45 min. Conversion of the reaction was found to be 70% under sonication. In comparison the reaction was carried out under silent condition (other charge is same as above) took 5 h for completion the completion of reaction was found to be 37% toward 3, 4-Dimethyl-benzenesulfonic acid.
EXAMPLE 6
The charge similar to that of given in example 1 was taken except that m-xylene was used instead of toluene. The reaction was completed in 45 min. Conversion of the reaction was found to be 82% under sonication. In comparison the reaction was carried out under silent condition (other charge is same as above) took 5 h for completion the completion of reaction was found to be 10% towards 2, 4-Dimethyl-benzenesulfonic acid.
EXAMPLE 7
The charge similar to that of given in example 1 was taken except that p-xylene was used instead of toluene. The reaction was completed in 45 min. Conversion of the reaction was found to be 76% under sonication. In comparison the reaction was carried out under silent condition (other charge is same as above) took 5 h for completion the completion of reaction was found to be 70% toward 2, 5-dimethyl-benzenesulfonicacid.

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EXAMPLE 8
The charge similar to that of given in example 1 was taken except that chloro
benzene was used instead of toluene. The reaction was completed in 45 min. Conversion
of the reaction was found to be 10% under sonication. In comparison the reaction was
carried out under silent condition (other charge is same as above) took 5 h for completion
the completion of reaction was found to be 1-2% toward 4-chloro-benzene sulfonic acid.
It implies from these examples that ultrasound promotes a selective sulfonation of
aromatic compounds with a significant enhancement in the rate of the reaction and
selective product formation

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We Claim:
1. An improved process for selective and rapid sulfonation of aromatic compounds using sulfuric acid as sulfonating agent and ultrasound as promoter having frequency range between 20-100 KHz.
2. A process as claimed in claim 1 wherein the sulfonating agent is only Cone. H2SO4 (48-98%).
3. A process as claimed in claim 1 where in the molar ratio of aromatic compound to sulfuric acid ranges from (1:3)
4. A process as claimed in claim 1 where in the starting material comprises of aromatic compounds such as toluene, benzene, naphthalene, chloro benzene, anisole, o-xylene, m-xylene, p-xylene etc.
5. A process as claimed in claim1 for sulfonation of aromatic compounds under solvent free condition.
6. A process as claimed in claim 1 for sulfonation of aromatic compounds in the temperature range of 20-60 °C with ultrasound as promoter.
7. A process as claimed in claim1 where in the ultrasound bath used for the process had a frequency of 33 KHz and electric power of 100W.
Date 03-06-2008 Signature

Documents:

1176-MUM-2008-ABSTRACT(10-11-2010).pdf

1176-MUM-2008-ABSTRACT(21-3-2011).pdf

1176-MUM-2008-ABSTRACT(3-6-2008).pdf

1176-MUM-2008-ABSTRACT(GRANTED)-(16-5-2011).pdf

1176-MUM-2008-CANCELLED PAGES(10-11-2010).pdf

1176-MUM-2008-CLAIMS(AMENDED)-(10-11-2010).pdf

1176-MUM-2008-CLAIMS(AMENDED)-(21-3-2011).pdf

1176-MUM-2008-CLAIMS(GRANTED)-(16-5-2011).pdf

1176-mum-2008-claims.doc

1176-mum-2008-claims.pdf

1176-MUM-2008-CORRESPONDENCE(21-3-2011).pdf

1176-MUM-2008-CORRESPONDENCE(IPO)-(30-5-2011).pdf

1176-mum-2008-correspondence.pdf

1176-mum-2008-description(complete).doc

1176-mum-2008-description(complete).pdf

1176-MUM-2008-DESCRIPTION(GRANTED)-(16-5-2011).pdf

1176-mum-2008-form 1.pdf

1176-MUM-2008-FORM 18(4-6-2008).pdf

1176-mum-2008-form 19.pdf

1176-MUM-2008-FORM 2(GRANTED)-(16-5-2011).pdf

1176-MUM-2008-FORM 2(TITLE PAGE)-(GRANTED)-(16-5-2011).pdf

1176-mum-2008-form 2(title page).pdf

1176-mum-2008-form 2.doc

1176-mum-2008-form 2.pdf

1176-mum-2008-form 3.pdf

1176-mum-2008-form 5.pdf

1176-mum-2008-form 9.pdf

1176-MUM-2008-REPLY TO EXAMINATION REPORT(10-11-2010).pdf

1176-MUM-2008-SPECIFICATION(AMENDED)-(10-11-2010).pdf

1176-MUM-2008-SPECIFICATION(AMENDED)-(21-3-2011).pdf


Patent Number 247765
Indian Patent Application Number 1176/MUM/2008
PG Journal Number 20/2011
Publication Date 20-May-2011
Grant Date 16-May-2011
Date of Filing 03-Jun-2008
Name of Patentee BHANAGE BHALCHANDRA MAHADEO
Applicant Address DEPARTMENT OF CHEMISTRY, INSTITUTE OF CHEMICAL TECHNOLOGY, UNIVERSITY OF MUMBAI, NATHALAL PAREKH MARG, MATUNGA (EAST), MUMBAI-400019,
Inventors:
# Inventor's Name Inventor's Address
1 QURESHI ZIYAUDDIN SHAHABUDDIN DEPARTMENT OF CHEMISTRY, INSTITUTE OF CHEMICAL TECHNOLOGY, UNIVERSITY OF MUMBAI, NATHALAL PAREKH MARG, MATUNGA (EAST), MUMBAI-400 019
2 NANDURKAR NITIN SUBHASH DEPARTMENT OF CHEMISTRY, INSTITUTE OF CHEMICAL TECHNOLOGY, UNIVERSITY OF MUMBAI, NATHALAL PAREKH MARG, MATUNGA (EAST), MUMBAI-400 019
3 DESHMUKH KRISHNA MANOHAR DEPARTMENT OF CHEMISTRY, INSTITUTE OF CHEMICAL TECHNOLOGY, UNIVERSITY OF MUMBAI, NATHALAL PAREKH MARG, MATUNGA (EAST), MUMBAI-400 019
4 BHANAGE BHALCHANDRA MAHADEO DEPARTMENT OF CHEMISTRY, INSTITUTE OF CHEMICAL TECHNOLOGY, UNIVERSITY OF MUMBAI, NATHALAL PAREKH MARG, MATUNGA (EAST), MUMBAI-400019
PCT International Classification Number C07B45/02
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA