Sulfuric monoesters

Some substituted alkyl hydrogen sulfates are readily prepared. For example, 2-chloroethyl hydrogen sulfate [36168-95-1] is obtained by treating ethylene chlorohydrin with sulfuric acid or amidosulfiiric acid. Heating hydroxy sulfates of amino alcohols produces the corresponding sulfuric monoester... 

Fig. 2. Synthesis of uma2enil (18). The isonitrosoacetanihde is synthesized from 4-f1iioroani1ine. Cyclization using sulfuric acid is followed by oxidization using peracetic acid to the isatoic anhydride. Reaction of sarcosine in DMF and acetic acid leads to the benzodiazepine-2,5-dione. Deprotonation, phosphorylation, and subsequent reaction with diethyl malonate leads to the diester. After selective hydrolysis and decarboxylation the resulting monoester is nitrosated and catalyticaHy hydrogenated to the aminoester. Introduction of the final carbon atom is accompHshed by reaction of triethyl orthoformate to...

The sulfites have some laboratory use, but are not commercially important and are less known. Monoesters of sulfurous acid are quite unstable, although salts have been identified. The diesters of sulfurous acid are mostly Hquids with boiling points somewhat less than those of the corresponding sulfates. 

Sulfate monoesters can react by dissociative paths, and this is the favored path. Whether such reactions are concerted or involve a very short-lived sulfur trioxide intermediate has been the subject of debate. ° Benkovic and Benkovic reported evidence suggesting that the nucleophile is present (though there is little bond formation) in the transition state for the reaction of amines with p-nitrophenyl sulfate. Alkyl esters of sulfuric or sulfonic acids normally react with C-0 cleavage only when this is disfavored, as in aryl esters, does one see S-0 cleavage. Sulfate diester... 

Plant maintenance/repair costs, 9 533 Plant monoesters, 26 204 Plant nutrient sulfur, 23 589 Plant operation... 

Fig. 1.13 Negative mode single quadrupole MS spectra of sulfuric acid monoester of 3-hydroxy retinoic acid (A) electrospray, (B) atmospheric pressure chemical ionization.

Acid-Catalyzed Synthesis. - 3.2.1 The Fundamentals. Homogeneous acid catalysts, such as sulfuric acid, phosphoric acid, hydrochloridric acid, organo sulfonic acids and others, can be used to catalyze the transesterification of TGs and the esterification of FFAs to produce biodiesel type monoesters. Nevertheless, because the acid-catalyzed transesterification is about 3 orders of magnitude slower than the alkali-catalyzed reaction for comparable amounts of catalyst, base catalysts have received the most attention in both the academic and industrial sectors. In addition, the corrosiveness of strong liquid acids and... 

In contrast, the acid-catalyzed hydrolysis of alkyl selenates is A-2158. The actual species which undergoes decomposition to alcohol and sulfur trioxide is probably the zwitterion as in the case of phosphate monoester monoanions. Evidence for sulfur trioxide as the reactive initial product of the A-1 solvolysis is obtained from the product compositions arising with mixed alcohol-water solvents. The product distribution is identical to that found for sulfur trioxide solvolysis, with the latter exhibiting a three-fold selectivity for methanol. Although the above entropies of activation and solvent deuterium isotope effects do not distinguish between the conventional A-l mechanism and one involving rate-limiting proton transfer, a simple calculation, based on the pKa of the sulfate moiety and the fact that its deprotonation is diffusion controlled. 

The available studies imply that general catalysis will be operative in systems involving sulfate monoesters and potential six-membered ring transition states. Salicyl sulfate hydrolyzes at pH 4 via intramolecular carboxyl group participation involving pre-equilibrium proton transfer leading to sulfur trioxide expulsion (Fig. 9)2HH, viz. 

This reaction provides a useful way of introducing a double bond next to a carbonyl group. Here it is in a synthesis by Barry Trost of the Queen Bee Substance (the compound fed by the workers to those bee larvae destined to become queens). The compound is also a pheromone of the termite and is used to trap these destructive pests. Trost started with the monoester of a dicarboxylic acid, which he converted to a methyl ketone by reacting the acyl chloride with a cuprate. The ketone was then protected as a dioxolane derivative to prevent it enolizing, and the sulfur was introduced by reacting the enolate of the ester with the sulfur electrophile MeSSMe. 

The earliest petrochemical process to convert ethylene to ethanol was first practiced in about 1930, and was indirect. In this process ethylene, under pressure, is absorbed by countercurrent passage against sulfuric acid (90-98%) at about 80°C in an absorber to form a mixture of the monoesters, and diesters (Eqs. 19.29 and 19.30). 

These comparative studies constituted the first example of an enzyme-catalyzed hydrolysis reaction whose stereochemical course was unaffected by sulfur substitution. At the time these experiments were performed, the stereochemical courses of the reactions catalyzed by glycerol kinase (83, 84) and by the bacterial adenylate cyclase (85, 86) had already been compared in the laboratories of Knowles and Gerlt, respectively, and these were also found to be unaffected by the sulfur substitution. A number of other comparisons of this type have been made, and in no case were the stereochemical consequences of the reactions studied with chiral phosphate esters and the chiral thiophosphate analogs found to differ. This agreement suggests that the necessary use of oxygen chiral thiophosphate monoesters to study the stereochemical course of phospho-monoesterases will provide pertinent results for ascertaining whether phosphory-lated intermediates are involved in the reaction mechanism. 

Phosphoric and sulfuric acid derivatives possess crucial properties that allow them to uniquely fill their many roles in biochemistry. Phosphoric acid may be esterified to form a monoester, diester, or triester (Figure 1). Sulfuric acid may be esterified at one or two positions, to form a monoester or a diester. Sulfate diesters are highly reactive, and have not been found in nature nor do phosphate triesters occur naturally. The hydrolysis of both phosphate and sulfate esters are thermodynamically favorable, but nucleophiles are repelled by the negative charge of the ionized forms. The resulting kinetic stability of phosphate monoesters and diesters, and of sulfate monoesters, is a major factor in their suitability for biological roles. For example, the half-life for hydrolysis of alkyl phosphate dianions by water is approximately 1.1 X 10 years k=2 x 10 s ) at 25°C. Such species... 

Sulfuryl transfer has available the same mechanistic pathways previously discussed for phosphoryl transfer (Figure 2). If a monoester follows a fully dissociative (D A ) mechanism, a sulfur trioxide intermediate would form, analogous to metaphosphate in the phosphoryl system. An addition—elimination (A D ) mechanism would form a pentacoordinate sulfurane intermediate. 

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