Cychc sulfates

Stabihty depends mosdy on purity, with purer materials having longer shelf Hves (1). For the higher alkyl groups, the anhydrous compounds are soluble and the monohydrates are insoluble in ether. Solutions in water are strongly ionized and acidic. The lower dialkyl sulfates are Hquids with faint but pleasant odors n-nonyX and higher normal aHphatic and cycHc sulfates are soHds. 

These reactions iavolve mostly dimethyl and diethyl sulfate. CycHc sulfates are also reactive, and several have been compared by determining reaction rates with a substituted pyridine or with water (40). In both cases, 1,2-ethylene sulfate is more reactive than 1,3-propylene sulfate or dimethyl or diethyl sulfates. 

CycHc sulfates can be prepared by a vahety of methods. Ethylene sulfate is obtained in low yield from ethylene oxide and sulfur thoxide (100). Methylene sulfate is produced from formaldehyde and sulfur thoxide (101). 

Oxidation of cycHc sulfites with permanganate in acetic acid solution gives cycHc sulfates (102). Heating monohydroxyalkyl hydrogen sulfates with thionyl chlohde causes ring closure (103). 

Acidolysis of cycHc sulfites with sulfuhc acid and ester interchange with dimethyl sulfate produce cycHc sulfates (104). 

The advent of sulfamate ester oxidative cyclization makes available a myriad of oxathia-zinane derivatives from simple alcohol precursors. These unusual heterocycles have enjoyed only sparing use despite their potential as electrophiHc azetidine equivalents. By contrast, five-membered ring sutfamidates and cycHc sulfates are broadly recog-... 

Megia-Femandez, A., Ortega-Munoz, M., Hemandez-Mateo, F., and Santoyo-Gonzalez, F. 2012. One-pot three-component chck reaction of cychc sulfates and cychc sulfamidates. Adv. Synth. Catal. 354(9) 1797-1803. 

Particles are the major cause of the ha2e and the brown color that is often associated with smog. The three most important types of particles produced in smog are composed of organics, sulfates, and nitrates. Organic particles are formed when large VOC molecules, especially aromatics and cycHc alkenes, react with each other and form condensable products. Sulfate particles are formed by a series of reactions initiated by the attack of OH on SO2 in the gas phase or by Hquid-phase reactions. Nitrate particles are formed by... 

The basic flow sheet for the flotation-concentration of nonsulfide minerals is essentially the same as that for treating sulfides but the family of reagents used is different. The reagents utilized for nonsulfide mineral concentrations by flotation are usually fatty acids or their salts (RCOOH, RCOOM), sulfonates (RSO M), sulfates (RSO M), where M is usually Na or K, and R represents a linear, branched, or cycHc hydrocarbon chain and amines [R2N(R)3]A where R and R are hydrocarbon chains and A is an anion such as Cl or Br . Collectors for most nonsulfides can be selected on the basis of their isoelectric points. Thus at pH > pH p cationic surfactants are suitable collectors whereas at lower pH values anion-type collectors are selected as illustrated in Figure 10 (28). Figure 13 shows an iron ore flotation flow sheet as a representative of high volume oxide flotation practice. 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

CycHc esters show accelerated hydrolysis rates. Ethylene sulfate compared to dimethyl sulfate is twice as fast ia weak acid (first order) and 20 times as fast ia weak alkaH (second order) (50). Catechol sulfate [4074-55-9] is 2 x 10 times faster than diphenyl sulfate ia alkaline solution (52). Alcoholysis rates of several dialkyl sulfates at 35—85°C are also known (53). 

Alkylation with a vatiety of common alkyl halides oi sulfates gives stable dialkylcyanamides. However, the intermediate monoalkylated compounds usually cannot be isolated and cychc trimers or cotrimers with cyanamide ate obtained (13). The reaction can be carried out efficientiy in water or alcohol. Allyl chloride is an especially useful reagent, producing diallylcyanamide [538-08-9J (4). 

In this contribution, we present new results of a cychc voltanunetiy study of the influence of (CeHglads on Hypo and on anion adsorption at the Pt(l 11) electrode in aqueous HCIO4 and H2SO4, and relate them to analogous studies at Pt(110) and Pt(lOO) electrodes in aqueous H2SO4. Perchlorate anions are known to be less strongly adsorbed on Pt than bisulfate or sulfate anions thus, the cychc voltanunetiy behavior in the two electrolytes is expected to reveal important differences. 

The typical S-oxidation with BVMOs allows the formation of chiral sulfoxides from organic sulfides. This oxidation has received much interest in organic chemistry due to its use in the synthesis of enantiomerically enriched materials as chiral auxiliaries or directly as biologically active ingredients. This reaction has been studied extensively with CHMO from Adnetohacter showing high enantioselectivi-ties in the sulfoxidation of alkyl aryl sulfides, disulfides, dialkyl sulfides, and cychc and acyclic 1,3-dithioacetals [90]. CHMO also catalyzes the enantioselective oxida-hon of organic cyclic sulfites to sulfates [91]. 

The activation of a diol function could be performed in many different ways. As will be discussed later, vicinal diols can be easily transformed into epoxides, halohydrins and cyclic sulfates, all of them reacting readily and with high stereocontrol with a range of nucleophiles. An intermediate typically generated during the formation of cyclic sulfates [113] is the corresponding cyclic sulfite (Scheme 37). Several nucleophiles, e.g. N3, Cl and Br react readily with activated cychc sulfites to afford in good yield and with clean inversion of stereochemistry, the substitution products. 

The mechanism of the Claus reaction is complicated, and the sequence of the surface reaction steps is not fioUy elucidated (361). The primary step is certainly the strong adsorption of SO2 on acid—base pairs with formation of sulfite and bisulfite species (354—356), which later react with gaseous or weakly adsorbed H2S. The strength of the SO2 adsorption depends on the surface basicity, which is influenced by the amount of sodium present (225) however, it must be taken into account that the reactivity of the formed sulfites is lower on more basic surface sites. Thus, the acid—base properties of the catalyst play a key role in this reaction. According to Clark et al. (362), sulfate and thiosulfate species apparently form in addition to the sulfites. It was proposed that sulfate and thiosulfate react to form [HS404] ions, which then react with H2S to form the S3 sulfur polymorph, which is subsequently converted into cychc Se and Sg molecules. 

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