Sulfolane solutions

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. 

Alkyl esters are efficiently dealkylated to trimethylsilyl esters with high concentrations of iodotrimethylsilane either in chloroform or sulfolane solutions at 25-80° or without solvent at 100-110°.Hydrolysis of the trimethylsilyl esters serves to release the carboxylic acid. Amines may be recovered from O-methyl, O-ethyl, and O-benzyl carbamates after reaction with iodotrimethylsilane in chloroform or sulfolane at 50—60° and subsequent methanolysis. The conversion of dimethyl, diethyl, and ethylene acetals and ketals to the parent aldehydes and ketones under aprotic conditions has been accomplished with this reagent. The reactions of alcohols (or the corresponding trimethylsilyl ethers) and aldehydes with iodotrimethylsilane give alkyl iodides and a-iodosilyl ethers,respectively. lodomethyl methyl ether is obtained from cleavage of dimethoxymethane with iodotrimethylsilane. 

Bollinger, J. C., Faure, R., Yvernault, T. Stahl, D. (1987). On the existence of the protonated dication in sulfolane solution. Chemical Physics Letters,... 

According to a patent [Y. Tokitoh, T. Higashi, K. Hino, M. Murosawa and N. Yoshimura, US Patent 5 057 631 (1991), to Kuraray Industries] the reaction is conducted with butadiene in sulfolane / water in the presence of Pd(OAc)2 as catalyst precursor and a soluble triarylphosphine (or its phosphonium bicarbonate, which is formed from octadienol itself and carbon dioxide) as ligand. The selectivity to 2,7-octadien-l-ol is 92-94% (TOF > 1000), while the isomeric l,7-octadien-3-ol accounts for another 3 5%. The product is extracted with hexane, while the aqueous sulfolane solution, containing the catalyst ca. 1 mmol/1) and triethylamine, is recycled. In the absence of carbon dioxide, the main product is 1,3,7-octatriene, an open-chain butadiene dimer. 

Materials. Sulfolane (99%purity) (Aldrich) was treated with calcium hydride and distilled under reduced pressure. The freshly prepared solvent had a specific conductivity of 1.0 X 10 7 O"1 cm"1 and a residual water content of 8 X 10"3M as determined by Karl Fisher titration. Conductivity water and reagent grade ether (Baker) were used. Glacial acetic acid (CIL), trifluoroacetic acid (Baker), and trifluoro-methanesulfonic acid (3M) were used as received. All these acids had a minimum purity of 99.5% as determined by titration with standard sodium hydroxide. Methanesulfonic acid (Eastman), distilled under reduced pressure, had a purity of 99.6%. Sulfolane solutions of these acids were prepared by weight, and the acid concentrations were checked by acidimetry after the samples were flooded with water. The solutions... 

Figure 1. Vapor pressure of sulfolane solutions of electrolytes as a function of water concentration at 30°C (O), sulfolane (A),...

Figure 4. Specific conductance of sulfolane solutions of acids as a function of diethyl ether concentration at 30°C ( ), 0.48M HCFsCOt (A), 0.58M HCHaSOs (6), 0.58M HCF SO(O), 0.25M HCFsSOs ( ), 0.15M HSbCls (C8bCH/CHCl = 0.33).

Table I. Heats of Mixing of Water with Sulfolane Solutions of Electrolytes at 30°C...

The rate constants of the reaction CH3Y + X- CH X + Y in sulfolane solution are described by the Marcus equation the quadratic term contributes very little. The Marcus equation then reduces to the expression log kyx = My + Nx, where My is a property of CH3Y only and Nx is a property of CG X only. Each term includes only the identity rates and the equilibria for methylation of a reference nucleophile. The two terms are determined independently of unsymmetric rate measurements, in contrast to the Swain-Scott equation. Short tables of both terms are presented. Extension to other solvents and to other reactions including group transfers is discussed. With other alkyl groups, the simple expression may cover the continuum from elimination-addition to addition-elimination and may also cover other group transfers. 

Anhydrous hydrogen fluoride and fluorosulfuric acid were found as improved solvents for the nitration of methane with nitronium salts. In these strong acid solvents even under the mild reaction conditions (room ten jerature) at least tenfold increased yields ( %) could be obtained. As no protolytic reactions of methane take place in HF under the reaction conditions, side reactions are not observed. This is not the case in the nitration of isobutane in HF solution, where 90 of the nitroalkanes obtained consisted of l-nitro-2-methylpropane. Since only traces of this iscmer were found in nitronium salt nitration in aprotic CH2Cl2-sulfolane solution, the formation of l-nitro-2-methylpropane must be considered due to formation of isobutylene (either frcm isobutane itself in HF containing PFc or more probably frcm the protolytic cleavage of 2-nltro-2-meuhylpropane). 

Powell and Whiting made a kinetic study of the isomerization of tra/is-A -octalin and A -octalin in 33% benzene-67% acetic acid and 33% benzene-67% sulfolane solutions at 30°C, viz. 

Specific conductivity of nitronium tetrafluoroborate varies linearly with concentration. Cryoscopic measurements in sulfolane solution indiate that the nitronium salt is present as ion pairs and the conductance must be due to ion triplets and not separated ions [54]. 

The IV-nitropyridinium and A -nitroquinolinium salts are stable (but moisture sensitive) crystalline reagents, well characterized by spectroscopic methods (NMR, IR, Raman). They are prepared in essentially quantitative yield by the slow addition of the corresponding pyridine to an equivalent amount of the nitronium salt in acetonitrile, nitromethane. or sulfolane solution. It is important to add the pyridine to the solution of the nitronium ion, because excess pyridine present during the reaction can lead to opening of the pyridinium ring. The iV-nitropyridinium salts can be used as isolated compounds or they can be generated in situ. 

Nitrodesilylation with nitronium tetrahuoroborate is also a mild and efficient way to prepare aiiphatic nitrocompounds from readily available alkylsilanes. Olah and Rochin have studied [151] the scope of the reaction, Tetramethylsilane reacts readily with NOJBFJ in sulfolane solution to give nitromethane in 80% yield. 

---