Methanesulfonate ion

Displacement of the methanesulfonate ion from the 5//-2-bcnzazepine 36 by methoxide produces, unexpectedly, the 3-methoxy-377-2-benzazepine 37.7 8... 

Methanesulfonate ion Trifluoromethanesulfonale ion 4>Melhylbenzene ulfonate ion (Mesylate ion) (IViflate ion) (p>Toluene ulfonate ion,... 

Nearly all commercial acetylations are realized using acid catalysts. Catalytic acetylation of alcohols can be carried out using mineral acids, eg, perchloric acid [7601-90-3], phosphoric acid [7664-38-2], sulfuric acid [7664-93-9], benzenesulfonic acid [98-11-3], or methanesulfonic acid [75-75-2], as the catalyst. Certain acid-reacting ion-exchange resins may also be used, but these tend to decompose in hot acetic acid. Mordenite [12445-20-4], a decationized Y-zeohte, is a useful acetylation catalyst (28) and aluminum chloride [7446-70-0], catalyzes / -butanol [71-36-3] acetylation (29). 

Zinc chloride is a Lewis acid catalyst that promotes cellulose esterification. However, because of the large quantities required, this type of catalyst would be uneconomical for commercial use. Other compounds such as titanium alkoxides, eg, tetrabutoxytitanium (80), sulfate salts containing cadmium, aluminum, and ammonium ions (81), sulfamic acid, and ammonium sulfate (82) have been reported as catalysts for cellulose acetate production. In general, they require reaction temperatures above 50°C for complete esterification. Relatively small amounts (<0.5%) of sulfuric acid combined with phosphoric acid (83), sulfonic acids, eg, methanesulfonic, or alkyl phosphites (84) have been reported as good acetylation catalysts, especially at reaction temperatures above 90°C. 

In contrast to the behavior of homoallylic alcohol (70a) when treated with methanesulfonyl chloride is pyridine, heating A -19-methanesulfonate (68b) in pyridine gives the 5)5,19-cyclo-6-ene (72). Vinylcyclopropane (72) is inert to the conditions used for converting vinylcyclopropane (73) to the A ° -B-homo-7)5-ol (70a). The latter results are only consistent with the existence of two discrete isomeric carbonium ion intermediates which give rise to isomeric elimination products. °... 

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... 

Numbers used in this cycle AG° for dissociation of methyl methanesulfonate to methanesulfonylinm ion and methoxide, assumed to be the same as for dimethyl sulfate, estimated above AG° for ionization of methanol. )... 

The freezing point depression of a solvent is proportional to the concentration of solute particles and may be used to measure the extent of ionization once the new particles have been identified qualitatively as ions. The method has the obvious disadvantage of not allowing measurements over a range of temperatures in a single solvent. It is almost certainly not worth while to compute an enthalpy of ionization from ionization constants at two different temperatures in two different solvents. Usable solvents are limited not only by the requirement that the melting point be at a convenient temperature but also by the requirement that the solvent be capable of producing ions yet not be sufficiently nucleophilic to react irreversibly with them once they are formed. For this reason most cryoscopic work has been done in sulfuric acid or methanesulfonic acid.170... 

A nucleophilic attack at an allene system of the type of 417 was described for the first time by Cainelli et al. [172], namely at 444 with the chloride ion as the nucleophile (Scheme 6.91). After the treatment of the mesylate 443 with triethylamine in the presence of lithium, sodium or tetrabutylammonium chloride, mixtures of the vinyl chlorides 445 and 447 were isolated in high yields. Since the reaction did not proceed in the absence of triethylamine, the first step should be a /3-elimination of methanesulfonic acid from 443 to generate 444, which would accept a chloride ion at the central allene carbon atom. A proton transfer to either allyl terminus of the anion thus formed (446) would lead to the products 445 and 447. 

Allylic carbonium ions 1+ -+ 2 2 R-CH-CH-. CH2 AUyl methanesulfonate lasiocarpine safrole... 

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