Sulfating agents

Because phenoHc compounds are easily sulfonated, their sulfation must be accompHshed with mil der sulfating agents, eg, complexes of sulfur thoxide or chlorosulfonic acid with trimethyl amine, dimethylform amide, pyhdine, or dim ethyl a n i1 in e, in anhydrous or aqueous medium below 100°C (86-89). 

G. Sulfation of alcohols with miscellaneous sulfation agents 232... 

The advance of sulfur trioxide as sulfating agent largely depended on advances in sulfonation/sulfation reactor development and changes in raw material quality. Undiluted sulfur trioxide cannot be used as a sulfating agent except in special cases where suitable equipment is used because of its violent nature. Sulfur trioxide diluted in an inert gas, usually air, when used in batch processes can cause excessive dehydration and dark-colored products. However, batch processes were used years ago and inert liquid solvents were often suggested or used to moderate the reaction. Inadequate reaction conditions lead to a finished product that can contain dialkyl sulfate, dialkyl ether, isomeric alcohols, and olefins whereas inadequate neutralization conditions can increase the content of the parent alcohol due to hydrolysis of the unstable acid sulfate accompanied by an increase of mineral sulfate. 

G. Sulfation of Alcohols with Miscellaneous Sulfation Agents... 

A variety of sulfating agents has been used for preparing sulfuric esters of polysaccharides.297 - 303 The methods employed include use of adducts of sulfur trioxide with such aprotic solvents as triethylamine,299 dimethyl... 

Sulfamic acid is a mild sulfating agent and is used only in very speciahzed quality areas because of the high reagent price. A process flow diagram is shown in Figure 12. Washouts are the only wastewater effluents from this process as well. 

Sulfation of hydroxyamino acids can possibly be carried out with all the sulfating agents described in Section 6.6.1.1,1381 but experimental details have only been reported for the method of sulfation with concentrated sulfuric acid11301 and with chlorosulfonic acid/TFA.1771... 

Table 5 Results for the sulfation of carboxymethyl dextran with different sulfating agents applying 2-methyl-2-butene (2M2B) as an acid scavenger (reaction temperature 30 °C, [110]) ...

Sulfating agent Molar ratio reagent/AGU DScm DSs Reducing sugars (nmol Glu mg-1)... 

The most significant instance of addition of a sulfur-containing group is the phase II conjugation to sulfate of a xenobiotic compound or its phase I metabolite (see Section 7.4.3) by the action of adenosine 3 -phosphate-5 -phosphosulfate, a sulfotransferase enzyme that acts as a sulfating agent ... 

The simultaneous sulfation of several hydroxyls has been accomplished with the same reagents discussed above, that is, sulfur trioxide pyridine90 or sulfur trioxide- trialkylamine complexes.91 Prolonged reaction times or repeated treatment with the sulfating agent may be needed to achieve complete sulfation. 

In sulfation, other sulfating agents may be used, such as oleum or chlorosulfonic acid, as the source of SO3. However, oleum generates a large amount of waste sulfuric acid. It is also not recommended for the sulfation of fatty alcohol ethoxylate. 

Chlorosulfonic acid is an excellent sulfating agent, but it generates unwanted hydrochloric acid as a byproduct. As a result of the corrosive nature of the hydrochloric acid vapor, special equipment must be used. 

The latest technology in the manufacture of fatty alcohol sulfate or fatty alcohol ether sulfate is the direct use of SO3 gas as the sulfating agent. This process not only produces a high-purity product but is also much more economical and generates minimum waste. 

The observation of L-ascorbic acid 2-0-sulfate, 18, in a number of animal species, including humans, has provoked extensive research into the chemistry and biochemistry of this inorganic ester of ascorbic acid (J, 19,20). Ascorbic acid 2-0-sulfate has been implicated as a biological sulfating agent and proposed as an anticholesteremic agent (21-24). 

Sulfamatlons are also efficiently carried out by use of CISO3H (77 ). A diethyl ether-ClS03H complex can be used as a milder sulfating agent than CISO3H alone. 

---