Process for the preparation of cyclic sulphates

##STR1## A method for preparing cyclic sulphates having general formula (I), wherein sulphuric anhydride and an alkylene oxide are simultaneously added to the dioxane. In general formula (I), R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and are a hydrogen atom of a C.sub.1-4 alkyl radical optionally substituted by a halogen atom.

FIELD OF THE INVENTION 
The present invention relates to a process for the preparation of cyclic 
sulphates of general formula: 
##STR2## 
in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4, which are identical or 
different, denote a hydrogen atom or an alkyl radical containing 1 to 4 
carbon atoms, optionally substituted by a halogen atom. 
BACKGROUND OF THE INVENTION 
It is known to prepare cyclic sulphates by reaction of sulphuric anhydride 
with an alkylene oxide, the operation being carried out in dioxane (U.S. 
Pat. No. 3,045,027) or in another organic solvent such as in 
dichloroethane (U.S. Pat. No. 3,154,526 or U.S. Pat. No. 3,167,572) or in 
gaseous phase at a temperature below 140.degree. C. (U.S. Pat. No. 
3,100,780). However, these processes do not make it possible to obtain 
cyclic sulphates in satisfactory yields. 
DETAILED DESCRIPTION OF THE INVENTION 
It is now been found, and this is what forms the subject of the present 
invention, that cyclic sulphates of general formula (I) can be obtained in 
yields which are generally higher than 80% by simultaneously adding 
sulphuric anhydride and the alkylene oxide to dioxane, optionally in the 
presence of a halogenated aliphatic hydrocarbon such as 
1,2-dichloroethane. 
To make use of the process according to the invention it is particularly 
important to operate under well-defined conditions. 
More precisely, the molar ratio of sulphuric anhydride to the alkylene 
oxide must be maintained at a constant value of between 1.01 and 1.07 
throughout the addition period. It is advantageous to maintain the ratio 
in the vicinity of 1.04. 
A quantity of dioxane is generally employed such that the molar ratio of 
dioxane to the alkylene oxide used is between 1 and 30. When ethylene 
oxide is employed as the alkylene oxide the ratio is preferably close to 
7. 
The reaction temperature is generally between 30 and 60.degree. C., 
preferably between 40 and 50.degree. C. 
It is particularly advantageous to employ anhydrous dioxane, which can be 
obtained, for example, by azeotropic distillation before the introduction 
of sulphuric anhydride and of the alkylene oxide. 
The sulphuric anhydride employed is preferably technical anhydride which is 
in liquid form (practically free from linear and/or crosslinked polymers). 
The alkylene oxide employed may be introduced in liquid or gaseous form, 
depending on its nature. 
The cyclic sulphate of general formula (I) obtained by making use of the 
process according to the invention may be either employed as it is after 
removal of dioxane by fast distillation, or purified by dissolving, after 
flash distillation of the dioxane, in a suitable organic solvent such as a 
halogenated aliphatic hydrocarbon like methylene chloride, followed by 
washing of the organic solution with sulphuric acid, optionally in aqueous 
solution, and then with water until neutral: the cyclic sulphate is 
obtained after evaporation of the solvent. 
The process according to the invention is particularly useful for preparing 
ethylene sulphate, propylene sulphate and 1-chloromethylethylene sulphate.

EXAMPLES 
The following examples, given without any limitation being implied, show 
how the invention can be put into practice. 
Example 1 
2000 g (22.7 moles of dioxane) are introduced into a 2.5-liter glass 
reactor fitted with a stirrer. 500 g of dioxane are distilled off at 
atmospheric pressure in order to remove the water present in the solvent. 
After cooling the residual dioxane (1500 g; 17.0 moles) to 45.degree. C., 
189 g of sulphuric anhydride (2.36 moles) and 100 g of ethylene oxide 
(2.27 moles) are added in parallel in 100 minutes while the sulphuric 
anhydride/ethylene oxide molar ratio is kept strictly equal to 1.04 and 
while the temperature is maintained at 45.degree. C. 
When the addition is complete, the reaction mixture is stirred for another 
30 minutes at 45.degree. C. 
After cooling, the determination of the reaction mixture 
- by high performance chromatography (HPLC) shows that the yield of 
ethylene sulphate is 90% relative to the ethylene oxide used, 
- by gas phase chromatography (GPC) shows that the degree of conversion of 
ethylene oxide is 100%. 
After removal of dioxane by distillation at reduced pressure (20 mm Hg; 2.6 
kPa), the crude ethylene sulphate, which is 82% pure, is extracted with 
1200 g of dichloromethane. The chloromethylene solution is washed with 
concentrated sulphuric acid and then with water and is finally dried over 
sodium sulphate. After filtering and concentrating to dryness, 232 g of 
ethylene sulphate are obtained in the form of a white powder melting at 
99.degree. C., its purity being 97%. 
Example 2 
2100 g of dioxane (23.9 moles) are introduced into a 2.5-liter glass 
reactor fitted with a stirrer. 300 g of dioxane are distilled off at 
atmospheric pressure in order to remove the water present in the solvent. 
After cooling the residual dioxane (1800 g; 20.5 moles) to 40.degree. C., 
77.8 g of sulphuric anhydride (0.97 moles) and 40 g of ethylene oxide 
(0.91 moles) are added in parallel in 60 minutes, while the sulphuric 
anhydride/ethylene oxide molar ratio is kept strictly equal to 1.07 
throughout the addition period and while the temperature is maintained at 
40.degree. C. 
When the addition is complete, the reaction mixture is stirred for another 
30 minutes at 40.degree. C. 
After cooling, the determination of the reaction mixture: 
- by HPLC shows that the yield of ethylene sulphate is 95% relative to the 
ethylene oxide used, 
- by GPC the degree of conversion of ethylene oxide is 100%. 
After removal of the dioxane by distillation at reduced pressure (20 mm Hg; 
2.6 kPa), the crude ethylene sulphate, which is 88% pure, is extracted 
with 500 g of dichloromethane. The chloromethylene solution is washed with 
concentrated sulphuric acid and then with water until neutral and is 
finally dried over sodium sulphate. After filtering and removing the 
solvents, 103.5 g of ethylene sulphate are obtained in the form of a white 
powder melting at 99.degree. C., its purity being 97%. 
Example 3 
1800 g of dioxane (20.5 moles) are introduced into a 2.5-liter glass 
reactor fitted with a stirrer. 300 g of dioxane are distilled off at 
atmospheric pressure in order to remove the water present in the solvent. 
After cooling the residual dioxane (1500 g; 17.0 moles) to 45.degree. C., 
189 g of sulphuric anhydride (2.36 moles) and 132 g of propylene oxide 
(2.26 moles) are added in parallel in 100 minutes, while a sulphuric 
anhydride/propylene oxide molar ratio is kept strictly equal to 1.04 
throughout the addition period and while the temperature is maintained at 
45.degree. C. 
When the addition is complete, the reaction mixture is stirred for another 
30 minutes at 45.degree. C. 
After cooling, the determination of the reaction mixture by HPLC shows that 
the yield of propylene sulphate is 76% relative to the propylene oxide 
used, 
After the usual treatment, propylene sulphate is obtained, its boiling 
point being 80.degree. C. at a pressure of 1 mm Hg (0.3 kPa). 
Example 4 
1800 g (20.5 moles) of dioxane are introduced into a 2.5-liter glass 
reactor fitted with a stirrer. 300 g of dioxane are distilled off at 
atmospheric pressure in order to remove the water present in the solvent. 
After cooling the residual dioxane (1500 g; 17.0 moles) to 45.degree. C., 
189 g of sulphuric anhydride (2.36 moles) and 210 g of epichlorohydrin 
(2.27 moles) are added in parallel in 100 minutes, the sulphuric 
anhydride/epichlorohydrin molar ratio being kept strictly equal to 1.04 
throughout the addition period and the temperature being maintained at 
45.degree. C. 
When the addition is complete, the reaction mixture is stirred for another 
30 minutes at 45.degree. C. 
After cooling, determination of the reaction mixture by HPLC shows that the 
yield of 1-chloromethylethylene sulphate is 79% relative to the 
epichlorohydrin used. 
After the usual treatment, 1-chloromethylethylene sulphate which has the 
following characteristics is obtained: 
- infrared spectrum (in solution in dichloromethane): characteristic 
absorption bands at 1398, 1214, 891, 651 and 535 cm.sup.-1, 
- mass spectrum (i.e.):M/Z (%)=172(8), 123(100), 137(5). 
Example 5 
208 g (2.36 moles) of dioxane and 1263 g of 1,2-dichloroethane (1000 
cm.sup.3) are introduced into a 2.5-liter glass reactor fitted with a 
stirrer. The reaction mixture is heated to 45.degree. C. 189 g of 
sulphuric anhydride (2.36 moles) and 132 g of propylene oxide (2.26 moles) 
are introduced in parallel in 70 minutes, the sulphuric 
anhydride/propylene oxide molar ratio being kept strictly equal to 1.04 
throughout the addition period and the temperature being maintained at 
45.degree. C. 
When the addition is complete, the reaction mixture is stirred for another 
30 minutes at 45.degree. C. 
After cooling, determination of the reaction mixture by HPLC shows that the 
yield of propylene sulphate is 84% relative to the propylene oxide used. 
Example 6 
208 g (2.36 moles) of dioxane and 1263 g of 1,2-dichloroethane (1000 
cm.sup.3) are introduced into a 2.5-liter glass reactor fitted with a 
stirrer. The reaction mixture is heated to 45.degree. C. 189 g of 
sulphuric anhydride (2.36 moles) and 210 g of epichlorohydrin (2.27 moles) 
are introduced in parallel in 69 minutes, the sulphuric 
anhydride/epichlorohydrin molar ratio being kept strictly equal to 1.04 
throughout the addition period and the temperature being maintained at 
45.degree. C. 
When the addition is complete, the reaction mixture is stirred for another 
30 minutes at 45.degree. C. 
After cooling, determination of the reaction mixture by HPLC shows that the 
yield of 1-chloromethylethylene sulphate is 87% relative to the 
epichlorohydrin used. 
Although the invention has been described in conjunction with specific 
embodiment, it is evident that many alternatives and variations will be 
apparent to those skilled in the art in light of the foregoing 
description. Accordingly, the invention is intended to embrace all of the 
alternatives and variations that fall within the spirit and scope of the 
appended claims. The above references are hereby incorporated by reference 
.