Claims
- 1. An improvement in the method of producing organic sulphoxides selected from the group consisting of dialkyl sulphoxides bearing a total of 2 to 36 carbon atoms, their corresponding hydroxy-substituted alkyl sulphoxides and polymethylene sulphoxides having 2 to 6 carbon atoms, by oxidizing a sulfide selected from the group consisting of dialkyl sulfides of formula R.sup.1 --S--R.sup.2 having a total of 2 to 36 carbon atoms and wherein R.sup.1 and R.sup.2 are chosen from a group consisting of alkyl and hydroxyalkyl groups, and polymethylene sulfides of formula ##STR4## wherein n is an integer of 0 to 4, with hydrogen peroxide in a reaction medium of an aqueous acidic medium and a solvent selected from the group consisting of benzene, toluene, hexane, heptane, dichloroethane, chloroprene, propyl acetate and isobutyl acetate, said solvent forming an azeotropic mixture with between 5 and 20% by weight of water, said solvent having the capacity for dissolving the dialkyl sulfides, while leaving the sulphoxide substantially undissolved at a temperature substantially below the boiling point of said mixture, and
- separating the sulphoxide formed from the reaction medium by distilling the azeotropic mixture from the solvent after the oxidation has been effectuated and allowing said medium to cool to the point where a precipitation of sulphoxide is formed.
- 2. An improvement as recited in claim 1, wherein the solvent is hexane.
- 3. An improvement as recited in claim 1, wherein the solvent is heptane.
Parent Case Info
This is a continuation, of application Ser. No. 644,718, filed Dec. 29, 1975 now abandoned, which is a continuation of application Ser. No. 545,487 filed Jan. 30, 1975 now abandoned.
Different sulphoxides are finding increasing use at the present time, especially in the form of solvents, as intermediates for the preparation of other compounds, additives to detergent baths and polymerisation emulsions. Their manufacture, therefore, is of interest to industry. The most commonly used known process is based upon the oxidation of the corresponding sulphide with hydrogen peroxide solution and can produce good yields. However, the separation of the sulphoxide from the reaction medium presents difficulties which become particularly troublesome when the sulphoxide is soluble in water. In fact, when the desired product is liquid, it is necessary to recover it from the reaction medium by distillation, which reduces the yield, often to below 70%. Besides this, impurities, such as water and sulphide, are always entrained by the product during distillation, so that it is never completely pure.
On the other hand, when the sulphoxide is solid it is very difficult to recover it by crystallization, since few solvents are capable of extracting such compounds from an aqueous medium. This necessitates the use of large volumes of solvent, and the yield of extract is not satisfactory. For example, in the case of di(hydroxy-2-ethyl) sulphoxide prepared by the oxidation of thiodiglycol with hydrogen peroxide, the yield is not more than 70% and the product is obtained in the form of a paste which must be dried for a long time under vacuum.
These difficulties militate against the large-scale production of certain sulphoxides, more especially those that are soluble in water.
The present invention provides improvement in the preparation of organic sulphoxides, particularly the aliphatic and hydroxyaliphatic sulphoxides. It enables the oxidation of sulphides with hydrogen peroxide to be carried out with greatly increased yields and a considerable improvement in the purity of the final products.
The new process according to the invention, which involves the transformation of the organic sulphide into the corresponding sulphoxide with hydrogen peroxide, is a method of producing a dialkyl-sulphoxide by oxidizing the corresponding dialkyl-sulphide with hydrogen peroxide in a solvent, wherein the solvent is one capable of forming an azeotropic mixture with water and wherein the azeotropic mixture is distilled off from the reaction medium after the oxidation has been effected.
When carrying out the invention, having completed the oxidation, the reaction medium is boiled so as to distil off the azeotrope with the complete elimination of water. Depending on the solubility of the sulphoxide in the solvent employed, the product may remain in solution in the excess solvent or it may precipitate or settle out from suspension. This facilitates its subsequent recovery by precipitation, crystallization, decantation or other means, after the partial or total elimination of the remaining solvent.
Various solvents may be used which include in particular benzene, toluene, hexane, heptane, dichloroethane, chloropropene, propyl acetate and iso-butyl acetate, whose azeotropes contain between 5% and 20% by weight of water.
The new principle, provided by the invention permits the technique for separating the final product to be varied by the choice of the azeotrope-forming solvent. In fact, one can choose a solvent which dissolves both the raw material and the end product, or one in which the sulphide is soluble and the sulphoxide insoluble. An interesting example of the latter is provided by heptane, which dissolves sulphides in the cold but not sulphoxides, facilitating their precipitation at the end of the reaction.
In the new process of the invention, it is not necessary to employ large quantities of acetic acid, if this is used, but a small catalytic proportion is sufficient, and this may be replaced by another organic acid capable of forming peracids by reaction with hydrogen peroxide.
It is understood that the organic solvent, having served to entrain the water in the form of an azeotrope, may be recovered after distillation and separation of the aqueous layer, so that the economy of the new process is not jeopardized by its use.
As indicated above, an important new application of certain sulphoxides is their use as thickening agents in various compositions, especially oil-based products, paints and cosmetics. In this last field, the sulphoxide acts the part of a thickener in formulations based upon the surface active agents of either the anionic, cationic, nonionic or amphoteric type. Although a large number of sulphoxides are suitable for these diverse applications, aliphatic sulphoxides containing two C.sub.1 -C.sub.18 alkyl groups, which may be the same or different, are particularly useful and the alkyl groups may carry hydroxyls or form a polymethylene ring.
The sulphides used in carrying out the method according to the invention have the formula R.sup.1 --S--R.sup.2 where R.sup.1 and R.sup.2, which may be the same or different, are preferably selected from alkyls and hydroxy-alkyls having 1 to 18 carbon atoms. More especially, one or both of the groups R.sup.1 and R.sup.2 are preferably C.sub.1 to C.sub.4 alkyls or hydroxy-alkyls.
In the preparation of particularly useful sulphoxides, sulphides are used in which R.sup.1 is an alkyl or hydroxy-alkyl having 1 to 3 carbon atoms, while R.sup.2 is a C.sub.6 to C.sub.12 alkyl.
Another kind of sulphoxide can be prepared starting from sulphides of the formula ##STR1## in which n is 0, 1, 2, 3, or 4, preferably 1 or 2.
One particularly advantageous process according to the invention comprises dissolving 1 mole of a dialkyl-sulphide as above defined in about 700 to 1400 ml of heptane, adding to the solution a catalytical amount of an acid, for instance 5 to 20 ml of pure acetic acid and/or 5 to 20 ml of an N/10 aqueous solution of perchloric acid, and substantially 1 mole of H.sub.2 O.sub.2, heating the mixture until the boiling temperature of the azeotropic heptane-water mixture is reached, allowing the azeotropic mixture to distil off, and then separating the sulphoxide thus formed from the remaining dry heptane.
The H.sub.2 O.sub.2 is preferably used in form of its commercial aqueous solution containing about 30 to 35% of H.sub.2 O.sub.2.
The invention is illustrated in the following Examples, which show the preparation of 10 different sulphoxides, as well as some of their applications.
US Referenced Citations (2)
| Number |
Name |
Date |
Kind |
| 3773838 |
Andruski et al. |
Nov 1973 |
|
| 3849499 |
Malievsky |
Nov 1974 |
|
Continuations (2)
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Number |
Date |
Country |
| Parent |
644718 |
Dec 1975 |
|
| Parent |
545487 |
Jan 1975 |
|
Patent Grant
4108866
