Tetramethylene sulfone solvent, polar

As normally polymerized, PVF melts between IH5 and 210 °C and contains 12 18% inverted monomer units ft is normally considered a thermoplastic, but because of its instability above its melting point, it cannot be processed by conventional thermoplastic techniques Instead it is generally extruded into films in a solvent swollen (organosol) form and the solvent is subsequently evaporated and recovered Such films can be onented further to achieve specific mechanical properties PVF films are exceptionally weather and radiabon resistant considenng their modest fluonne content PVF is insoluble below 100 °C but, at higher temperatures, it dissolves in polar solvents like amides, ketones, tetramethylene sulfone, and tetramethylurea Resistance to acids and bases at room temperature IS good [1, 29 ... 

Formamidc has been found to be a very suitable solvent for fluoride displacement reactions on optically active substrates leading to more reduced racemization that is in comparison to other aprotic solvents like tetramethylene sulfone, l,3-dimethyl-3,4,5,6-tetrahydropyrimidin-2(l/7)-one etc.146 Formamide has a high polarizability favoring SN2 reactions and a high polarity147 rendering potassium fluoride sufficiently soluble in the reaction mixture. Although the reaction rate is reduced, the less polar solvents A-methylformamide, acetamide or A-methyl-acetamide can also be used as solvents for the reaction. 

The recognition that polar solvents such as MeCN, tetramethylene sulfone, benzonitrile, and others greatly increase the activity of the alkali metal fluorides NaF and KF has led to their widespread use in metathesis reactions. Potassium fluoride is more active than NaF but the latter is easily dried and does not readily absorb H2O. Many fluorinations are readily accomplished by refluxing the halide with excess NaF in the solvent in standard glass apparatus or by heating under autogenous pressure in an autoclave. Some examples of useful fluorinations are shown in equations (23 -28). It was recently found that the reactivity of KF is enhanced when used in ionic liquids. ... 

The influence of solvent polarity on the rate of quatemization is well known and recent measurements have supported the general view that the more polar solvents produce a faster reaction. Fuoss and his colleagues determined the rate of reaction in a number of solvents and discovered that the process was twice as fast in tetramethylene sulfone as in propylene carbonate, even though the dielectric constants of these solvents are 42 and 65, respectively. In another study a mixture of diphenyl ether with propylene carbonate and ethylene carbonate was used to cover the range of dielectric constants from 3.6 to 65. The reactions showed second-order kinetics up to 90% completion except for pure diphenyl ether where the rate decreased with time and was truly second order only up to 10%. It was found that solvent mixtures containing more than 50% propylene... 

The reaction is usually carried out at high temperatures (of about 200°C) in a polar solvent, such as tetramethylene sulfone, and the polyamide formation can be accelerated by the addition of l-phenyl-3-methyl-2-phospholene 1-oxide as catalyst. However, in the case of a two-step process, the reaction time of the first step must be carefully controlled, since the catalyst can also play a role in the formation of carbodiimides from two terminal isocyanate groups [36], These carbodiimides can then further react and lead to crosslinking [36], In most cases [34-39], the polymers are prepared with 4,4 -methylene bis(phenyl-isocyanate) (MDI), using adipic acid, isophtahc acid, azelaic acid, or a mixture of two of them (in order to accelerate the solubilization of the polyamide phase in the solvent) and a polyether based on tetramethylene oxide, ethylene oxide, or a mixture of propylene oxide and ethylene oxide. 

A new facile method for the rapid synthesis of aliphatic polyamides and polyimides was developed by using a domestic microwave oven to facilitate the polycondensation of both w-amino acids and nylon salts as well as of the salt monomers composed of aliphatic diamines and pyromellitic acid or its diethyl ester in the presence of a small amount of a polar organic medium. Suitable organic media for the polyamide synthesis were tetramethylene sulfone, amide-type solvents such as A -cyclohexyl-2-pyrrolidone (CHP) and 13-dimethyl-2-imidazolidone (DMI), and phenolic solvents like m-cresol and c)-chlorophenol, and for the polyimide synthesis amide-type solvents such as A-methyl-2-pyrrolidone, CHP, and DMI. In the case of the polyamide synthesis, the polycondensation was almost complete within 5 min, producing a series of polyamides with inherent viscosities around 0.5 dL/g, whereas the polyimides having the viscosity values above 0.5 dL/g were obtained quite rapidly by the microwave-assisted polycondensation for only 2 min. 

In fact, highly polar solvents such as water, 13-diniethyl-2-imidazolidone (DMI), and tetramethylene sulfone (sulfolane) generated heat quickly by the microwave irradiation. For example, water (e = 78) was heated within 1 min to reach the boiling point near 100 C. Highly polar and high-boiling-point solvents such as DMI (e = 37 and bp 225"C) and sulfolane (e = 43 and bp 287"C) were heated to 180 C after 1 min of the microwave irradiation. The heat generation of less polar m-cresol (e = 12 and bp 202 C) was intermediate between that of water and DMI or sulfolane. 

The reduction of the capacity factors with increasing organic modifier concentration in the eluent was weaker when methanol was used compared to acetonitrile, and this was attribnted to its lower polarity [5]. Even if methanol or acetonitrile are the most common organic modifiers, an unusual solvent, tetramethylene oxide [16], was recently tested in the IPC of sulfides and aromatic sulfonated compounds and proved to play an important role in adjusting retention. 

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