Sulfate, acetyl

Other acetyl chloride preparations include the reaction of acetic acid and chlorinated ethylenes in the presence of ferric chloride [7705-08-0] (29) a combination of ben2yl chloride [100-44-7] and acetic acid at 85% yield (30) conversion of ethyUdene dichloride, in 91% yield (31) and decomposition of ethyl acetate [141-78-6] by the action of phosgene [75-44-5] producing also ethyl chloride [75-00-3] (32). The expense of raw material and capital cost of plant probably make this last route prohibitive. Chlorination of acetic acid to monochloroacetic acid [79-11-8] also generates acetyl chloride as a by-product (33). Because acetyl chloride is cosdy to recover, it is usually recycled to be converted into monochloroacetic acid. A salvage method in which the mixture of HCl and acetyl chloride is scmbbed with H2SO4 to form acetyl sulfate has been patented (33). 

Fmoc-Tyr(S03Na)-OH (3 equiv) DIC (3 equiv)/ HOBt (3 equiv) 2-chloro- trityl-resin AcOH/TFE/CH2C12 (1 1 3), 20 °C, 20 min /V-acetyl-sulfated Leu-enkephalin n.r. [149]... 

The same authors also report on the reaction of alkenes with chlorosulfuric acid in the absence of dioxane <1999EJ091 >. Thus, treatment of various alkenes at —40°C with chlorosulfuric acid results in the formation of, r-alkyl hydrogen sulfates (Scheme 16). From the results presented it appears that the rcr-alkyl hydrogen sulfates are transformed into a mixture of internal trans- and m-/3-sultones upon warming to 0 °C. Subsequent sulfonation of these alkenes by S03 then yields the corresponding /3-sultones. Again isolation yields were not reported but the reactions appear to proceed in a quantitative manner. The same paper also describes the use of acetyl sulfate and trifluoroacetyl sulfate for the preparation of /3-sultones, but mixtures appear to result. 

Mixed anionic (sulfonated - carboxylated) ionomers [81] were prepared by sulfonation of maleated block-copoly (styrene/ethylene-butylene/styrene) (m-SEBS) by acetyl sulfate, followed by neutralisation of the sulfonated maleated product, leading to the formation of a new block copolymer ionomer based on both carboxylate and sulfonate anions according to Scheme 4.6. FT-IR spectra confirm the presence of both carboxylated and sulfonate ions (Figure 4.9). 

A special class of lonomer in which the salt groups are only at the chain ends, i.e., telechellc ionomers, have recently received considerable attention as model lonomer systems. Kennedy and coworkers (86-88) prepared linear and tri-arm star telechellc sulfonated polyisobutylene by heterogeneous sulfonation of an olefin-terminated polyisobutylene with acetyl sulfate. Omels et... 

Polvisoprene/Polybutadiene (IPB) Star-Block Copolymers. The obsen-ed selective sulfonating capabilities of acetyl sulfate was the basis for the first attempted variation of the synthetic strategy. Regardless of the exact nature... 

The sulfonation of low molecular weight model olefins was undertaken to determine the feasibility of this approach. Competitive sulfonations using acetyl sulfate were carried out on the model compounds below, representing the repeat structures of cis-l,4-polyisoprene (PIP), cw-l,4-polybutadiene (c-PBD), and trans-l,4-polybutadiene (Z-PBD), respectively. It was necessary to model both the cis and trans isomeric forms of 1,4-polybutadiene, since ttey have a nearly equal probability of occurrence when the anionic polymerization (Ii counterion) is conducted in a nonpolar hydrocarbon medium... 

Figure 6. Competitive sulfonation of polyisoprene model compound vs. cis-l,4-polybutadiene model compound using acetyl sulfate. PIP c-PBD acetyl sulfate = 1 10 2 (mole). Temperature = 2rC. Solvent = decalin.

Sulfonation of the outer styrene units of the hydrogenated polymers has been conducted using methylene chloride solutions at room temperature. In order to sulfonate every phenyl ring in the sample, a large excess of acetyl sulfate has been us The reactions appear homogeneous with the... 

An interesting group of new ionomers have been prepared from liquid olefin telechelic polyisobutylenes. Syntheses involved the quantitative sulfonation (by acetyl sulfate) of linear and/or tri-arm star polyisobutylenes carrying exactly two or three -CH2-C(CH3)=CH2 termini, respectively, followed by neutralization with various bases ... 

The reagent acetyl sulfate for these studies was generated in two ways. In one case acetic anhydride and concentrated sulfuric acid were mixed at a temperature below 0°C, the thick solution warmed to about 10°C, and the preformed neat reagent added to the EPDM solution (cement). In the second case, the acetyl sulfate was generated in situ, i.e., acetic anhydride was added to the EPDM cement and then the concentrated sulfuric acid was dripped in. With the polymers previously described and according to the following procedures, results with the preformed and the in situ reagents were fully equivalent. 

The acetyl sulfate was generated from at least 1.6 mol of acetic anhydride per mol of concentrated sulfuric acid. 

Figure 1. Sulfonation of CR-2504 with in situ acetyl sulfate in heptane (%) sulfur analysis (O) titration. (Acetic anhydride = 1.62 polymer con-centration = 100 g/L temperature = 25°C time = 30 min).

Sulfonated Polystyrene (S-PS). The preparation of S-PS has been described in detail in Ref. 6. The following procedure was generally followed 104 g of PS (Styron 666 manufactured by Dow Chemical Company) were dissolved in 490 mL of 1,2-dichloroethane. The solution was heated to 50°C, and the requisite amount of acetyl sulfate was added, in this case, 30 mL of 0.996M acetyl sulfate (29.9 meq). The solution was stirred for 60 min at 50°C, and the reaction was terminated by the addition of 25 mL of methanol. Sufficient sodium hydroxide (diluted with methanol) was added to neutralize all acid present. The polymer solution was precipitated into a substantial excess of methanol with vigorous agitation, followed by filtration and washing with methanol. The product was then vacuum dried. Analyses were conducted for sulfur and sodium. The level of sulfonate incorporated was determined by sulfur analysis. 

Previous investigators have drawn attention to the beneficial effect of lime when added in small quantities to asphaltic bitumen. The lime helps retard oxidative hardening (13) and reduces the tendency towards water-stripping (4,11,12). Most asphalts are slightly acidic because of the presence of phenolic or carboxylic substituents and would therefore react with basic oxides to form insoluble salts. For example, Fromm (10) has described the use of iron salts of naphthenic acids as adhesion promoters to improve the water resistance of asphalt concretes. This promising approach is now undergoing commercial trials. The literature also describes methods of chemically modifying asphalt with maleic anhydride or acrylic acid (14), sulfur trioxide (15), sulfur dioxide (16), acetyl sulfate (17-21), and sulfuric acid (20). (For a recent review of the interfacial phenomena in asphaltic compositions see Ref. 4.)... 

Makowsky and coworkers30 sulfonated this rubber in hexane solution at room temperature using acetyl sulfate, preformed by reacting acetic anhydride with sulfuric acid. As in the case of the TEP S03 complex28, this attenuated reagent31 also effected a selective substitution in the a-position to the exocyclic vinyl double bond of the ethylidene-norbornene (EN) moiety, that was present in the rubber samples at a content of 4.4-7.5%. 

Phase II biotransformation involves the enzymatic conjugation of a polar molecule to the drug molecule or to the phase I metabolite. These reactions include glucuronidation, acetylation, sulfation, or amidation. 

Phase II reactions involve conjugation, sometimes after a phase 1 hydroxylation. The conjugation may be glucuronidation, acetylation, sulfation, or addition of glutathione. 

Phase 2 reactions (conjugation) are enzymatic syntheses whereby a functional group, such as alcohol, phenol, or amine, is masked by the addition of a new group, such as acetyl, sulfate, glucuronic acid, or certain amino acids, which further increases the polarity of the drug or xenobiotic. Most substances undergo both Phase 1 and Phase 2 reactions sequentially. 

The absolute purity of a biological substance is hard - if at all possible - to determine. Regular and sometimes only subtle protein modifications such as glycosyla-tion, alternative disulphide bond formation, deamidation, oxidation, phosphorylation, acetylation, sulfation, sulfoxidation, y-carboxylation, and pyroglutamate formation lead to protein variants that may have more or less different characteristics. Also, truncated protein variants might be generated by the presence of cryptic or alternative start sites of transcription, by premature stop of the peptide chain... 

For the sulfonation of PAES-Z7-poly(butadiene) block copolymers, acetyl sulfate, which can be prepared from acetic anhydride concentrated sulfuric acid, is used successfully. ... 

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