FORM 2
The Patent Act 1970,
(39 of 1970)
&
The Patent rule 2003
Complete Specification
(See Section 10 and Rule 13)
1. TITLE OF THE INVENTION
"Process to prepare exclusively 4,4'- isomer of the bis(4-Chlorobenzenesulfonyl)diphenyl sulfone."
2. APPLICANT(S)
(a) NAME : GHARDA CHEMICALS LTD
(b) NATIONALITY : INDIAN
(c) ADDRESS: B-27/29, MIDC, PHASE 1, DOMBIVLI.
DIST. THANE, PIN 421 203 MAHARASHTRA INDIA
3. PREAMBLE OF THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION
This invention relates to preparation of more specifically 4,4' isomer of monomeric sulfone of the formula

Where X = Halogen. For X= CI, the compound 4,4'-bis(4-chloroben2enesulfonyl)diphenylsulfone is prepared by reaction of an alkali metal salt of 4-chlorobenzenesulfinic acid and 4,4'-dichlorodiphenylsulfone having specific purity and reacting the substances while maintaining a specific temperatureand dipolar aprotic solvents like dimethylformamide(DMF),dimethylacetamide (DMAC), N-methyipyrrolidone (NMP), dipropylene glycol etc.
The compound 4,4'-bis(4-chlorobenzenesulfonyl)diphenyl sulfone is an important polymer intermediate and various polymers having this monomer unit have been prepared like Polysulfide sulfone and polysulfones.
BACKGROUND OF INVENTION
Sulfone monomers & Polysulfone polymers having the structure -Ar-S02- are known. US 4,517,354 describes Polysulfone compositions and derivatives thereof. Same patent discloses a preparation method of the said compound by condensation of diphenyl sulfone with 4-chlorobenzenesulfonyl chloride in the presence of FeCI3.
It is known in literature about the directive and activating influence of the sulfone group in the benzene ring. Sulfone group being electron withdrawing, is almost entirely meta directing. Hence reported route is most likely to give meta-oriented substitution and will not give exclusively 4,4'-isomer of bis (4-Chlorobenzenesulfonyl)diphenylsulfone with use of FeCI3 as catalyst.
SUMMARY OF THE INVENTION
Our method is to exclusively make the 4,4' isomer of a monomeric sulfone of the formula

in high yield and in high purity by blending of p-chlorobenzenesulfonyl chloride and an alkali metal salt of sulfite heated to a specific temperature to get 4-chlorobenzenesulfinic acid salt, which in turn is reacted with 4,4'-dichlorodiphenylsulfone having specific purity and reacting the substances while maintaining a specific temperature using dipolar aprotic solvents like dimethylformamide (DMF), dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), dipropylene glycol etc.

DETAILED DESCRIPTION OF THE INVENTION
0
Salts of sulfinic acids readily displace halide ions to form sulfone. For such reactions, hydroxytic solvents such as methanol or ethanol are commonly used. Higher boiling solvents such as dipolyethylene glycol, gives excellent yields. Since the advent of solvents known to facilitate nucleophilic displacements, such solvents as glyme and DMF have been used. Sodium or Potassium salt of para chlorobenzene sulfinic acid is prepared by the reaction of p-Chlorobenzenesulfonyl chloride and sodium/potassium sulphite to give para chlorobenzene sulfinic acid salt. Preferentially 2 to 2.5 mole of para chlorobenzene sulfinic acid salt is reacted with 1 mole of 4,4'-dichlorodiphenylsulphone preferably at 180 to 200°C in Dipolar aprotic solvents like DMF, DMAC, NMP, dipropylene glycol etc. Reaction time is generally 5 to 10 hrs. The practice of this invention is illustrated by the following examples. These examples are given merely by way of illustration and are not intended to limit the scope of the invention in any way nor the manner in which the invention can be practiced. Unless specifically indicated otherwise, parts and percentages are given as parts and percentages by weight.
Example 1:
Synthesis of 4,4'-bis(4-chlorobenzenesulfonyl)diphenylsulfone
In a one lit round - bottom flask equipped with a stirrer and reflux condenser, is placed 299 gram [1mole] of 4,4'-dichlorodiphenylsulphone, 401 gram [ 2.0 mole] of parachlorobenzene sulfinic acid salt and 500 ml Glyme. Reaction mass maintained at 180°C for 6 hrs. Reaction mass is cooled to 30°C, filtered. Cake is washed and dried to get 400 gram [70 % yield on theoretical] of product. The elemental analysis of C : 50.5 %.H : 2.8 %.S: 16.8 %.CI:12.1% are in good agreement with the theoretical values [MW 567] for a compound of the formula C24H16CI206S3.
Example 2 : In a one lit round - bottom flask equipped with a stirrer and reflux condenser, is placed 299 gram [ 1 mole] of 4,4'-dichlorodiphenylsulphone, 496.2 gram [ 2.5 mole] of para chlorobenzenesulfinic acid salt and 500 ml NMP. Reaction mass is maintained at 185°C for 6 hrs. Reaction mass is cooled to 30°C, filtered. Cake is washed and dried to get 410 gram [72 % yield on theoretical] of product.

We Claim,
1. A process for producing a 4,4' isomer of monomeric sulfone of the formula

Where X = Halogen.
2. The compound as claimed in claim 1 ( For X = CI) comprises of using an alkali metal salt of 4-chlorobenzenesulfinic acid and 4,4-dichlorodiphenylsulfone having specific purity and reacting the substances while maintaining a specific temperature using a dipolar aprotic solvents.
3. The specific temperature as claimed in claim 2 is in the range of 100 to 200°C, preferably at180°C.
4. The dipolar aprotic solvents as claimed in claim 2 are solvents like dimethylformamide(DMF), dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), dipropylene glycol etc.
Date 13th Dec. 2005
Abstract: -
The method disclosed herein comprises of a process to prepare exclusively 4,4'- isomer of a monomeric sulfone of the formula
Where X = Halogen, (For X= CI) the compound 4,4'-bis(4-chlorobenzenesulfonyl) diphenylsulfone in high yield and in high purity by blending an alkali metal salt of p-chlorobenzenesulfonyl chloride and sodium sulfite heated to a specific temperature to get 4-chlorobenzenesulfinic acid salt, which in turn is reacted with 4,4'-dichlorodiphenylsulfone having specific purity and reacting the substances while maintaining a specific temperature of 180 to 200°C and dipolar aprotic solvents like dimethylformamide(DMF), dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), dipropylene glycol etc. The compound 4,4'-bis( 4-chlorobenzenesulfonyl )diphenylsulfone is an important polymer intermediate.