FILED OF THE INVENTION:

The present invention relates to a new process to form 2-bromo-2-nitro-l-3-propanediol -Bronopol fused with Ammoniacal Nitrate Sulfate Bromide.

OBJECT OF THE INVENTION

The first object of the invention is to obtain 2-bromo-2-nitro-l-3-propanediol-Bronopol fused with Ammoniacal Nitrate Sulfate Bromide.

The second object of the invention is to have a new process for obtaining 2-bromo-2-nitro-1-3-propanediol-Bronopol fused with Ammoniacal Nitrate Sulfate Bromide.

SUMMARY OF THE INVENTION

A process of forming 2-bromo-2-nitro-l-3-propanediol (Bronopol) fused with Ammoniacal Nitrate Sulfate Bromide resulting in the formation of complex straight crystals. This process is through reacting 5-nitro-l-3-dioxane with Bromine liquid in the presence of strong metallic hydroxide (KOH, NaOH) in catalytic amounts. Addition of excess quantities of cold concentrated Sulfuric acid and liquor ammonia at the latter stages of the reaction is, to attain the end salts like complex straight crystals containing Bronopol in combination with Ammoniacal Nitrate Sulfate Bromide; in the course of the reaction desired proportion of ketones and mild alcohols like ethanol and methanol are also added to facilitate uninterrupted chemical reaction to occur following the anticipated pathways. This novel salt has proved to be an excellent bactericide.

DESCRIPTION OF THE INVENTION

More specifically in this process, 2-bromo-2-nitro-l-3-propanediol is produced in complex combination with Ammoniacal Nitrate Sulfate Bromide by reacting liquid formaldehyde with nitromethane in presence of metallic hydroxide (KOH, NaOH) at a minimum catalytic amount and also at higher concentration. Addition of strong metallic hydroxide is also mixed with sodium carbonate, which facilitates greater activity to arrive at the desired end product. The reaction mixture is also heated at times to have the temperature all the time at 20 to 30°C, so that the aqueous solution of the base when added, keep the reaction in an effectively controlled level. This base liquor is neutralized with liquid bromine. When liquid bromine is used, desired quantity of liquid bromine is added to neutralize the reagents; in addition, strong mineral acids are also added, which leads to Bronopol formation. The reaction of production of 2-bromo2- nitro-l-3-propanediol takes a few hours and the reaction is allowed to go through under controlled conditions, especially at temperature not exceeding 30°C. As the reaction is in progress, water is produced as a by-product, leading to dilution of the strong mineral acids like Sulfuric acid used for neutralizing. To achieve the end result, ie. production of the desired complex salts, steps are taken to add cold concentrated Sulfuric acid as a reactant, to ensure the presence of 50% concentration of Sulfuric acid in the reacting blend; to this combination of reactants, liquor ammonia is added or ammonia gas is allowed to pass through for neutralization. This reaction is conducted at a temperature not exceeding 30° C.

Charging the reactants to the reaction vessel is carried out by adding the desired chemicals gradually and ensuring constant stirring of the reactants so that ail reacting materials are allowed to go into contact at optimal level so that the reaction is completed and the complex salts precipitate from the acidic aqueous reaction mixture in the reactor.
The salient features of the process are in the selections such as:-

• Nitromethane and formaldehyde are reacted in the molar ratio of 3:4.

• The temperature of the reactor goes upto 40 to 50°C but is maintained to be around 20°C to30°C.

• The concentration of metallic hydroxide -50% and above in the blend;

• Metallic hydroxide and nitromethane molar ratio - 3.5 to 4.

• Reaction time - 4 to 6 hours.


Further another salient in the process, is that at the end of 5th hour, cold concentrated Sulfuric acid is added to make the reaction mixture to attain 50% and more of metallic acid like Sulfuric acid.

Further more to this reaction mixture, liquor ammonia is added at a level more than the acid portion of the reacting mixture and kept at around 20°C -30°C or ammonia gas is bubbled through with constant stirring at 100 RPM. The reaction to give Bronopol and fusing with Ammoniacal Nitrate Sulfate Bromide, steps are taken to neutralize the acid with enough of ammonia base. The reaction is exothermic, fast and stops immediately after completing the addition of feed of ammonia. The end of the reaction may be determined by the precipitation of crystalline salts. The temperature is reduced after the addition of the base and the complex salts precipitate as crystals. The reaction mixture is brought to room
temperature with 25 to 28"C and the stirring process, which so carried out till then, is slowly stopped. The crystals which separates consist essentially for Bronopol in complex combination with Ammoniacal Nitrate Sulfate Bromide.

The selectivity of the reaction produces more than 85% yield, based on the quantum of nitromethane taken in the reaction and also the quantities of Sulfuric acid and it's concentrate coupled with ammonia - for neutralization and the level of neutralization occurred in the production of ammoniacal salts as straight crystals coupled with Bronopol and Bromides.

The following steps will make the process and the preparatory procedures highly illustrative for understanding:-

Nitromethane is used as a starting material. It is generally commercially available. Nitromethane is used in molar concentration excess of other important reagents like formaldehyde, which selection is not known in prior art use of liquid formaldehyde in the process improves reaction velocity.

Formaldehyde that is deployed is normal formaldehyde liquid of 40% concentration. Since solid paraformaldehyde has very high molecular weight, 40% formaldehyde, which is in liquid form, is preferred for usage as nitromethane addition at higher molar level, facilitates greater chemical reaction velocity.

Paraformaldehyde usage, since it slows down the reaction, 40% formaldehyde is Preferred in the invention. Using of liquid formaldehyde leads to fast heat release and increase in temperature of the reactants. Care is taken to prevent reverse reaction leading to the production of unstable intermediaries through proper maintenance qf temperature at 20°C to 30°C. Water, nitromethane and formaldehyde are charged in the reaction vessel and made to remain at 20°C to 30°C. Optimal quantity of water is added to have an aqueous solution, facilitating addition of metallic alkali to be neutralized with bromine liquid and that Bronopol produced in the reaction dissolves in the aqueous reagent, 50 to 60% Bronopol is obtained on weight to weight basis. The reaction mixture containing all the three phases is stirred vigourously to assure an effective mixing of the reagents. The speed is controlled at not less than 100 rpm and the temperature maintained at 20°C to 30°C.

Water, nitromethane, formaldehyde, metallic alkali, sodium carbonate, mineral acid and bromine in the reaction vessel is maintained at 20°C to 30°C and properly agitated, to ensure optimal conditions for feeding the metallic hydroxide at desired level during the reaction . The addition of base is at minimal catalytic level; excess base is preferred, though at times it may prove costlier.

The Production of Tris (hydroxymethyl) nitromethane, which is important in getting greater quantum of bronopol production, with proper timely addition of reactants is ensured through addition of optimal proportion of reagents in addition to ethyl or methyl alcohol followed by addition of ketones.

The molar ratio between sodium hydroxide (catalyst base), nitromethane and bromine combination is kept between 4:100 and 6:100. The temperature must be maintained always between 20°C to 30°C, to deliver the base to the reaction zone.

The reaction time is 8 to 10 hours and the reaction time varies as per the rate of addition of base and maintenance of the temperature from the reaction mixture at optimal level, i.e. between 20°C to 30°C. The addition cold dilute addition of mineral acids (cold concentrated Sulfuric acid) allows the reaction to reach completion with moderate base consumption. HPLC studies are also conducted on the reaction mixture to ensure that the reaction proceeds with 2-bromo-2-nitro-l-3-propanediol with desired intermediaries.

The desired intermediary, which is 2-nitro-2-bromo-2-nitroethanol calls for addition of ethanol and/or methanol during the early stages of the reaction along with ketones. Further, in order to facilitate the reaction to proceed properly passing through all the stages
in a systematized manner, ketone is added, especially cyclohexane, to facilitate removal of excess water that is produced in the reaction as by-product. Distillation of excess water at appropriate stages is carried out through distillation. Since the boiling point of cyclohexane is more than water, cyclohexane is preferred.

When the reactants has the desired amount of water, addition of cold concentrated Sulfuric acid is resorted to, in order to bring mineral acid present in the reactants up to 50% concentration level or slightly above. At this stage, liquor ammonia is added with constant stirring or ammonia gas is bubbled through. Addition of liquor ammonia in excess of Sulfuric acid content is preferred. Passing of base reactant is stopped, once the reaction is nearing completion. Constant stirring is carried out till the end.

Once the reactions are completed, straight crystals of 2-bromo-2-nitro-l-3propanediol coupled with Ammoniacal Nitrate Sulfate Bromide are produced as single straight crystals of complex salt, which are separated through filtration, desiccation or vacuum dried.

Nitromethane + formaldehyde ► tris nitromethane -1 This is called Henry Reaction. Nitromethane and formaldehyde is contacted in a solvent, which could be from lower alkyl group -methanol in the presence of Na OH or KOH in catalytic proportion. 3 mole of formaldehyde per mole of Nitromethane. This Nitromethane is reacted with Ketone Alternatively to prevent the costly process of evaporating water. Tris nitromelthane(l) can be reacted with Venvl ether in the presence of H2SO4 Ethyl venyl ether methyl venyl ether
the resultant bi product alcohol does not interfere in the process.

This is exothermic reaction of 50/50. The cooling the vessel may be done conventional way and so also cooling the surrounding. 5 Nitro, -5 Bromo -1, 3, dioxane IV is then separated by filtration.

The temperature of this process is done at 20°C to 30°C. The water (excess) + concentrated sulfuric acid 30% w/v is evaporated to a limited level when the Bronopol is about to crystallize a slurry consistency of the reactants is formed. Then ammonia or add liquid ammonia is passed through to the slurry such that ammonium sulphate and bronopol complex salt are produced. Needle shaped crystals are formed.

The Ammonia gas is used to nutralise the moderate/dilute H2SO4 to form pure Ammonium sulphate, which complexes itself with Bronopol to produce a complex salt. The straight/crystal of Ammonium sulphate -Bronopol complex salt is crystalised th rough evaporation process or by cooling.

One of the preferred embodiment of the invention discloses a process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) which is bronopol fused with ammoniacal nitrate sulfate bromide. The steps involved in the process is as follow. First, charging a reaction vessel with nitromethane, liquid formaldehyde and water then gradually feeding a base into said reaction vessel under stirring at 100 rpm thereafter adding ketone for removing the excess by-product water formed in the reaction vessel, adding cold mineral acid which is cold concentrated sulfuric acid to the reaction vessel in which the concentration of sulphuric acid is 50%, adding liquor ammonia or passing ammonia gas under stirring wherein the stirring speed is 100 rpm, and bringing the reaction to completion and separating the complex salt. The base used in the process is metallic hydroxide at a minimum catalytic amount and also at higher concentration. The base is fed into the reaction vessel while the temperature in the reaction mixture is around 20-30°C and never greater than 30°C. The molar ratio between nitromethane and formaldehyde used in the process is 3:4 and the molar ratio between the total amount of base fed into the reaction vessel and nitromethane is 3.5:4. The base to nitromethane is in the range between 4:100 and 6:100. The base is fed to the reaction vessel in the form of an aqueous solution in which the concentration of the base is 50%. The formaldehyde used in the process is 40% formaldehyde in liquid form. The base is metallic hydroxide with sodium carbonate. Further, the base is neutralized with liquid bromine. The duration of reaction time is in the range of maximum of 5 to 6 hours for entire step and the addition of cold dilution of mineral acid is after 2 to 3 hours from initiating first step. The ketone used in the process is acetone, methyl ethyl ketone, diethyl ketone or cyclohexane and the ketone may be substituted with adding venyl ether in the presence of H2so4( wherein venyl ethyl may be ethyl venyl ether or methyl venyl ether.

As described above the end product is a complex salt of Bronopol ammonium sulphate and the process disclosed herein is novel hitherto unknown in prior art.

WE CLAIM:

1. A process for preparing a complex salt of bronopol ammonium sulphate (2-bromo- - nitro-l-3-propanediol) which is bronopol fused with ammoniacal nitrate sulfate bromide, which process comprises :

a. charging a reaction vessel with nitromethane, liquid formaldehyde and water,

b. gradually feeding a base into said reaction vessel under stirring at 100 rpm.

c. adding ketone for removing the excess by-product water formed in the reaction
vessel,

d. adding cold mineral acid which is cold concentrated sulfuric acid to the reaction
vessel in which the concentration of sulphuric acid is 50%,

e. adding liquor ammonia or passing ammonia gas under stirring wherein the
stirring speed is 100 rpm, and

f. bringing the reaction to completion and separating the complex salt.

2. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the said base is metallic hydroxide.

3. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the said base is at a minimum catalytic amount and also at higher concentration.

4. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the base is fed while the temperature in the reaction mixture is around 20-30°C.

5. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanedJol) as claimed in claim 1, wherein the base is fed while the temperature in the reaction mixture is never greater than 30°C.

6. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the molar ratio between nitromethane and formaldehyde is 3:4.

7. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the molar ratio between the total amount of base fed into the reaction vessel and nitromethane is 3.5:4.

8. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the base to nitromethane is in the range between 4:100 and 6:100.

9. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the base is fed to the reaction vessel in the form of an aqueous solution in which the concentration of the base is 50%.

10. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the said formaldehyde is 40% formaldehyde in liquid form.

11. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the base is metallic hydroxide with sodium carbonate.

12. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the base is neutralized with liquid bromine.

13. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the duration of reaction time is in the range of maximum of 5 to 6 hours for step (a) to (e).

14. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the addition of cold dilution of mineral acid is after 2 to 3 hours from initiating step (a).

15. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the ketone is acetone, methyl ethyl ketone, diethyl ketone or cyclohexane.

16. The process for preparing a complex salt of bronopol ammonium sulphate (2-bromo-2-nitro-l-3-propanediol) as claimed in claim 1, wherein the ketone may be substituted with adding venyl ether in the presence of H2so4, wherein venyl ethyl may be ethyl venyl ether or methyl venyl ether.