Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfonic acids or salts thereof
Reexamination Certificate
1999-01-19
2001-03-13
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfonic acids or salts thereof
Reexamination Certificate
active
06201149
ABSTRACT:
The present invention relates to the use of fluorosulphonates to release organic bases from their hydrofluoride, to hydrogen fluorosulphonates of an organic base, to processes for the preparation of fluorosulphonate(s) and to compositions of organic base fluorosulphonate(s) and of hydrofluoric acid. The invention relates more particularly to a technique for separating hydrofluoric acid from organic bases capable of forming combinations, usually constituting defined compounds, with several, at least three, molecules of unitary hydrofluoric acid (i.e. HF).
The process according to the present invention is particularly suitable for bases which constitute, with hydrofluoric acid, combinations containing more than two, advantageously three, hydrofluoric acid units.
It is well known to those skilled in the art that organic bases form, with hydrofluoric acid, complexes containing at least three hydrofluoric acid units. Generally, the weaker and softer the bases, the greater the number of hydrofluoric acid units per basic function.
Now, on account of their specific properties, fluoro compounds are in ever-increasing demand and used in applications such as agriculture and health.
Fluoro derivatives are often difficult to synthesize and often involve exchanges of various substituents with fluorine. Now, the reagent most commonly used and the cheapest for carrying out the exchange is undeniably hydrofluoric acid.
In addition, this acid is increasingly being used as a reaction medium. Certain precursors of organic bases present problems of stability, thus, carbamoyl fluorides show thermal instability which leads to the formation of isocyanate or to the formation of fluorophosgene (Hoechst, EP 639,556) which is very difficult to handle on account of its toxicity. Moreover, fluorophosgene leads to the loss of two fluorine atoms.
Accordingly, one of the aims of the present invention is to provide a form of organic bases whose use allows appreciable recovery of the hydrofluoric acid.
Another aim of the present invention is to provide a form of the above type whose use allows the hydrolysis of carbamoyl fluorides without releasing phosgenes and in particular fluorophosgenes.
Another aim of the present invention is to provide a process for preparing a form of the above type.
Another aim of the present invention is to provide a process for preparing a form of the above type which allows the release of the base from carbamoyl.
Another aim of the present invention is to provide a composition containing the said organic base and at least two equivalents of hydrofluoric acid per basic function, from which composition recovery of the hydrofluoric acid is easy.
These aims and others which will emerge later are achieved by means of using the hydrogen fluorosulphonate form of an organic base in order to separate it from the hydrofluoric acid which is combined with the said base or which is combined with one of its precursors.
Thus, in the course of the study which led to the present invention, it has been shown that fluorosulphonic acid (HFSO
3
) is capable of displacing complexes between organic bases and hydrofluoric acid, thus allowing the hydrofluoric acid to be recovered.
The present invention is especially of interest for certain bases, in particular phosphorus bases and especially nitrogen bases.
Thus, when the said base is a nitrogen base, it is advantageously chosen from amines (including cyclic amines) and imines (including aromatic heterocycles).
When the said base is a phosphorus base, it is advantageously chosen from phosphines (including cyclic phosphines), and aromatic heterocycles containing a phosphorus as hetero atom.
The greater the capacity of the said organic base to combine with hydrofluoric acid and the greater the number of hydrofluoric acid units with which it can combine, the greater the advantage of the present invention.
Thus, it is advantageous for the said organic base to be chosen from those whose pKa in combined form is not more than 8, advantageously not more than 7.
The said base is chosen from those capable of forming complexes with hydrofluoric acid in which the ratio between the hydrofluoric acid and the basic function (or at least one of the basic functions when the molecule treated contains several basic functions) is at least equal to 5.
As has been outlined above, the said base is combined with hydrofluoric acid in the form of one of its precursors.
According to one particularly advantageous embodiment of the present invention, the said precursor is a precursor which releases the said base by consuming a molecule of water. This characteristic has an advantage during the in-situ preparation of the fluorosulphonate anion, as will be seen later.
According to an advantageous variant of the present invention, in the said precursor, the function which will be converted into a basic function is a function which releases a gas such as, for example, carbon dioxide.
When the said base is an amine (including an aniline), a good example of a function which releases a gas (carbon dioxide) can be found in carbamic acid derivatives, such as urea, carbamoyl [often in the form of halide, usually fluoride] or carbamate functions. These functions are derived from isocyanate functions.
Given its cost, its relative instability and its corrosiveness, it is advantageous for the said hydrogen fluorosulphonate to be formed in situ.
Accordingly, one of the aims of the present invention is to provide a process which makes it possible to release a base from one of its complexes with hydrofluoric acid.
This aim and others which will become apparent later are achieved by means of a process which includes a step a) in which the hydrogen fluorosulphonate of the said organic base is formed.
Advantageously, this process includes, after step a), a step b) in which the hydrofluoric acid is recovered from the composition thus modified.
It is possible to form the hydrogen fluorosulphonate by a simple action of fluorosulphonic acid on the complex between the hydrofluoric acid and the said organic base. This is undoubtedly a satisfactory route when an inexpensive source of such an acid is available on site.
However, it is advantageous, and this is another aim of the present invention, to be able to prepare fluorosulphonate in situ, in particular from a composition containing hydrofluoric acid, optionally combined with an organic base.
Thus, in the course of the study which led to the present invention, it has been shown that fluorosulphonic acid can readily be manufactured in situ by the action of sulphuric acid or sulphur trioxide (sulphuric anhydride or SO
3
) on more or less anhydrous organic compositions containing hydrofluoric acid.
When the said composition is wet and/or contains no dehydrating agent, it is then advisable to use sulphur trioxide, SO
3
, in its native form or in the form of oleum.
If the said composition contains a dehydrating agent, it may then be advantageous to use sulphuric acid, optionally containing a small amount of water (sulphuric acid at a concentration at least equal to 80%, advantageously to 90%, often to 95%). Thus, in this embodiment of the present invention, the fluorosulphonic acid is manufactured in situ by the action of sulphuric acid on the hydrofluoric acid from the composition in the presence of a dehydrating agent.
Advantageously, the said dehydrating agent is a precursor of the said base.
The said organic base is an amine and the said precursor of the said base is an isocyanate function or a function which is derived therefrom (for example carbamoyl urea [halide, usually fluoride] or carbamate).
The reaction for the synthesis of the fluorosulphonic anion is carried out at a temperature of between 0° C. and 100° C., distillation temperature of HF, advantageously between 0° C. and 50° C., preferably between 0° C. and 20° C.
Although it is possible to envisage carrying out the said recovery of the hydrofluoric acid in a different manner, and in particular by liquid extraction, it is generally preferred for step b) of hydrofluoric acid recov
Morel Marcel
Saint-Jalmes Laurent
Burns Doane Swecker & Mathis L.L.P.
Killos Paul J.
Rhodia Chimie
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