Sulfurous acid esters

Table 1. Some Sulfuric and Sulfurous Acid Esters...

The sulfuric acid esters as compared to the sulfurous esters are the most widely used. In nature they appear as so1iibifi2ing groups in... 

Castor oil sulfation results largely in a sulfuric acid ester in which the hydroxyl group of ricinoleic acid has been esterified. However, other reactions can also take place. For example, the double bond can be attacked to produce an ester or the hydroxysulfonic acid (33). Hydrolysis of the sulfuric acid esters occurs during the reaction and subsequent treatment forming hydroxy acids and sulfuric acid. These hydroxy acids can be further sulfated. 

To a stirred solution of 4.6 g (0.01 mol) of anhydrous oxytetracycline in 40 ml of dry tetrahydrofuran is added 3.5 g (0.021 mol) of pyridine-sulfur trioxide complex. After 16 hours of stirring at room temperature, the resulting suspension is filtered, and the solid is slurried with 25 ml of 2% hydrochloric acid for 10 minutes, filtered and thoroughly washed with methanol followed by ether. The pale yellow crystalline 5-oxytetracycline-6, 12-hemiketal-12-sulfuric acid ester melts at 210°C. 

The sulfo nation steps are carried out at around 100°, using 4 to 4.5 moles of sulfuric acid per mole of phenol. The reaction proceeds thru an intermediate sulfuric acid ester ... 

Anionic Carboxylic acid salts Sulfuric acid ester salts Good detergency Good wetting agents Generally water-soluble Electrolyte-tolerant Electrolyte-sensitive... 

Sulfuric acid esters of xylan can be prepared118 by the method of Karrer. 

Some sulfatases (sulfuric ester hydrolases, EC 3.1.6) play a pharmacological role in the hydrolysis of sulfuric acid ester metabolites and the few such esters that are used as prodrugs. Arylsulfatase (sulfatase, arylsulfohydrolase,... 

EC 3.1.6.1) is a lysosomal enzyme that hydrolyzes sulfuric acid ester bonds. The enzyme exists in two forms, arylsulfatases A and B, that differ in substrate specificity and in sensitivity toward inhibitors [142][143]. Human tissues contain more arylsulfatase A than arylsulfatase B. The natural substrates of these enzymes are complex lipids such as cerebroside 3-sulfate, and gly-cosaminoglycans such as chondroitin 4-sulfate and derman sulfate [144], Deficiencies of these enzymes are associated with a number of lysosomal disorders. 

Hydrolysis of Sulfuric Acid Esters and Related Compounds... 

A number of enzymes known as sulfuric ester hydrolases (EC 3.1.6) are able to hydrolyze sulfuric acid esters. They comprise arylsulfatase (sulfatase, EC 3.1.6.1), steryl-sulfatase (steroid sulfatase, steryl-sulfate sulfohydrolase, arylsulfatase C, EC 3.1.6.2), choline-sulfatase (choline-sulfate sulfohydrolase, EC 3.1.6.6), and monomethyl-sulfatase (EC 3.1.6.16). Whereas mono-methyl-sulfatase is highly specific and does not act on higher homologues, arylsulfatase has a broad substrate specificity and is of particular significance in the hydrolysis of sulfate conjugates of phenols, be they endogenous compounds, drugs, or their metabolites [167-169],... 

Sulfuric acid esters also undergo chemical hydrolysis, which can be acid- or base-catalyzed [170], As a rule, the former reaction is faster than the latter, the slowest rates being found around neutrality. High dependence on chemical structure is another characteristic of sulfuric acid ester hydrolysis. 

In conclusion, we note the paucity of metabolic data on sulfuric acid esters, compared to the wealth of information on esters of N- and P-containing acids. One of the reasons for this state of affairs is presumably a lack of interest of medicinal chemists in preparing esters of S-containing acids. But because of the numerous applications of such compounds, is it hoped that more metabolic data will become available in a near future. 

SULFONIC ACID AND SULFURIC ACID ESTER TO NEUTRALIZATION... 

This step is essential in the manufacture of detergent active ingredients as it converts the sulfonic acids or sulfuric acid esters (products produced by processes I-M) into neutral surfactants. It is a potential source of some oil and grease, but occasional leaks and spills around the pump and valves are the only expected source of wastewater contamination. A process flow diagram is shown in Figure 14. 

Figure 14 Neutralization of sulfuric acid esters and sulfonic acids (N) (from Ref. 13).

Shortly after Anderson and Falvey reported the first observation of a shortlived nitrenium ion in CH3CN by UV spectroscopy, Novak and McClelland and co-workers demonstrated that the nitrenium ions 75h and 75o could be observed in aqueous solution after LFP of the pivalic acid ester 76h, the sulfuric acid ester 76o, and its N-chloro analogue N-chloro-4-phenylacetanilide. The transients with A ax of ca. 450 nm were identified as singlet nitrenium ions, based on the kinetics of their decomposition in the presence of NJ, the equivalence of kaz/ks determined by the azide clock method and by direct observation, the lack of sensitivity of the transients to O2, product studies that showed similar products from solvolytic and photolytic decomposition of N-chloro-4-phenylacetanilide, and identical transient UV spectra for 75o derived either from 76o or its N-chloro analogue. A comparison of azide/solvent selectivity data obtained by azide clock and direct observation of 7Sh and 75o is presented in Table 1. 

Acid-catalyzed reactions require the use of high alcohol-to-oil molar ratios in order to obtain good product yields in practical reaction times. However, ester yields do not proportionally increase with molar ratio. For instance, for soybean methanolysis using sulfuric acid, ester formation sharply improved from 77% using a methanol-to-oil ratio of 3.3 1 to 87.8% with a ratio of 6 1. Higher molar ratios showed only moderate improvement until reaching a maximum value at a 30 1 ratio (98.4%)." " " ... 

Chemical Abstracts refers to sulfites as sulfurous acid esters. Simple esters (benzyl, phenyl, ethyl, etc.) are listed as sulfurous acid esters under the names of the corresponding hydroxy compound. All mixed esters are indexed separately under the heading sulfurous acid esters. ... 

Water (28 g) and polyoxyethylene phenyl ether sulfuric acid ester emulsifier (0.08 g) were added to a 300-ml flask and heated to 85°C while stirring. This solution was then treated with a mixture of the step 4 product (6.3 g), methyl methacrylate (41.6 g), styrene (14 g), butyl acrylate (23.5 g), 2-ethylhexyl acrylate (14.6 g), water (51.6 g), polyoxyethylene phenyl ether sulfuric acid ester emulsifier (6.6 g), and 0.3 g of sodium persulfate over 4 hours. Thereafter, a mixture of water (5.2 g) and ammonium persulfate (0.1 g) were added over 30 minutes and the mixture stirred for an additional 2 hours. It was then cooled to ambient temperature and a white resin isolated, which consisted of 52% solids with a polymerization conversion of 99%. 

Since sulfur from the persulfate does not appear in the polymer, two possible reactions were suggested. The sulfate ion-radicals may initiate the polymerization to produce fluoroalkyl sulfuric acid esters which would be very rapidly hydrolyzed. 

The 13C NMR study of the polymerization of pent-l-ene with 95% H2SO4 points to the carbenium-ion mechanism, which involves the formation of sulfuric acid esters and their further heterolytic dissociation to generate aliphatic carbenium ions, whose steady-state concentration is low. By contrast, polymerization in 60-70% H2SO4 proved to occur via oxonium (rather than carbenium) ions.38... 

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