Dipolar aprotic solvents sulfolane

Nucleophilic Substitution Route. Commercial synthesis of poly(arylethersulfone)s is accompHshed almost exclusively via the nucleophilic substitution polycondensation route. This synthesis route, discovered at Union Carbide in the early 1960s (3,4), involves reaction of the bisphenol of choice with 4,4 -dichlorodiphenylsulfone in a dipolar aprotic solvent in the presence of an alkaUbase. Examples of dipolar aprotic solvents include A/-methyl-2-pyrrohdinone (NMP), dimethyl acetamide (DMAc), sulfolane, and dimethyl sulfoxide (DMSO). Examples of suitable bases are sodium hydroxide, potassium hydroxide, and potassium carbonate. In the case of polysulfone (PSE) synthesis, the reaction is a two-step process in which the dialkah metal salt of bisphenol A (1) is first formed in situ from bisphenol A [80-05-7] by reaction with the base (eg, two molar equivalents of NaOH),... 

Other salts, especially fluoride salts, (e.g., KF) can be used to perform nucleophilic substitution. As is well known, halides, and particularly the fluoride anions, are rather powerful Lewis bases and can exert a catalytic effect on aromatic nucleophilic substitutions in dipolar aprotic solvents. Phenols can be alkylated in the presence of KF (or CsF) absorbed on Celite64,65 or Et4NF.66 Taking advantage of this reaction, halophenols and dihalides with bisphenols have been successfully polymerized in sulfolane at 220-280°C by using KF as the base. 

Parker37 defined class 4 as solvents "which cannot donate suitable labile hydrogen atoms to form strong hydrogen bonds with an appropriate species and proposed the designation dipolar aprotic solvents he extended their range down to s > 15 and quoted as examples acetone, acetonitrile, benzonitrile, dimethylformamide, dimethyl sulphoxide, nitrobenzene, nitromethane (41.8) and sulfolane (tetramethylene sulphone) (44), where e varies from 21 to 46.5, and the dipole moment p from 2.7 to 4.7 debye. 

The linear products are generally soluble in such dipolar aprotic solvents as DMSO, DMF, HMPA, Sulfolane, acetone, and triethyl phosphate. 

Further improvements in dehalogenation selectivity and yields can be achieved by using dipolar aprotic solvents. Dimethylformamide has mostly been used for this purpose,18,56,84 97 although dimethyl sulfoxide,98,99 especially when combined with sonication at room temperature (vide infra), deserves attention in particular cases.100,101 Other polar and dipolar aprotic solvents have also been used, namely, acetone,4 butan-2-one,4 acetonitrile,102 acetic anhydride,103104 ethyl acetate,61 tetrahydrothiophene 1,1-dioxide (sulfolane)105 and hexamethyl-phosphoric triamide,106 but no details were reported on their advantages over dimelhylform-amide or dimethyl sulfoxide. Better performance of dipolar aprotic solvents, such as dimethyl-formamide, over other solvents has been demonstrated in the recent comparison of the dehalogenation of 4,5-dichloro-4,5,5-trifluoropentan-l-ol (4) with zinc in various solvents.90... 

A comparison of the suitability of solvents for use in Srn 1 reactions was made in benzenoid systems46 and in heteroaromatic systems.47 The marked dependence of solvent effect on the nature of the aromatic substrate, the nucleophile, its counterion and the temperature at which the reaction is carried out, however, often make comparisons difficult. Bunnett and coworkers46 chose to study the reaction of iodoben-zene with potassium diethyl phosphite, sodium benzenethiolate, the potassium enolate of acetone, and lithium r-butylamide. From extensive data based on the reactions with K+ (EtO)2PO (an extremely reactive nucleophile in Srn 1 reactions and a relatively weak base) the solvents of choice (based on yields of diethyl phenylphosphonate, given in parentheses) were found to be liquid ammonia (96%), acetonitrile (94%), r-butyl alcohol (74%), DMSO (68%), DMF (63%), DME (56%) and DMA (53%). The powerful dipolar aprotic solvents HMPA (4%), sulfolane (20%) and NMP (10%) were found not to be suitable. A similar but more discriminating trend was found in reactions of iodobenzene with the other nucleophilic salts listed above.46 Nearly comparable suitability of liquid ammonia and DMSO have been found with other substrate/nucleophile combinations. For example, the reaction of p-iodotoluene with Ph2P (equation (14) gives 89% and 78% isolated yields (of the corresponding phosphine oxide) in liquid ammonia and DMSO respectively.4 ... 

The use of dimethyl sulphoxide in organic chemistry has revealed the profound influence of solvent on the course and the rates of organic reactions. The striking discovery, in the early 1960 s, that certain dipolar aprotic solvents such as dimethylformamide (DMF), tetrahydrothiophene-1,1-dioxide (sulfolane), hexamethylphosphor-triamide (HMPT), as well as DMSO, could result in certain instances in rate enhancements of the order of 1010 relative to hydroxylic solvents led to a re-appraisal of the then established theories of medium effects. 

Another potential application of perfluorocarbons is their use as bulking agents where the volume of conventional solvent is reduced by replacement with a perfluorocarbon. Although the halex reaction is a successful industrial process, there are problems recovering the toxic dipolar aprotic solvents. Chambers [80] has shown that, on a preparative scale, up to 75% of the sulfolane can be replaced in the halex reaction by an equivalent volume of perfluorohydrophenanthrene (b. pt. = 215°C). On cooling the reaction mixture, it is a simple matter to separate off the fluorous solvent at the end of the reaction for recycling. 

In contrast, dipolar aprotic solvents possess large relative permittivities (sr > 15), sizeable dipole moments p > 8.3 10 ° Cm = 2.5 D), and average C.f values of 0.3 to 0.5. These solvents do not act as hydrogen-bond donors since their C—H bonds are not sufficiently polarized. However, they are usually good EPD solvents and hence cation sol-vators due to the presence of lone electron pairs. Among the most important dipolar aprotic solvents are acetone, acetonitrile [75], benzonitrile, A,A-dimethylacetamide [76, 77], A,A-dimethylformamide [76-78], dimethylsulfone [79], dimethyl sulfoxide [80-84], hex-amethylphosphoric triamide [85], 1-methylpyrrolidin-2-one [86], nitrobenzene, nitro-methane [87], cyclic carbonates such as propylene carbonate (4-methyl-l,3-dioxol-2-one) [88], sulfolane (tetrahydrothiophene-1,1-dioxide) [89, 90, 90a], 1,1,3,3-tetramethylurea [91, 91a] and tetrasubstituted cyclic ureas such as 3,4,5,6-tetrahydro-l,3-dimethyl-pyr-imidin-2-(l//)-one (dimethyl propylene urea, DMPU) [133]. The latter is a suitable substitute for the carcinogenic hexamethylphosphoric triamide cf. Table A-14) [134]. 

Tetrahydrofuran (THF) and dioxane are well-known solvents for organic reactions. iV-MethylpyrroMone (NMP) and sulfolane are useful dipolar aprotic solvents, with characteristics like those of dimethylfor-mamide (DMF) and dimethyl sulfoxide (DMSO). Saturated and partially unsaturated heterocycles occur widely as components of natural products (Chapter 32). 

Polysulfones Polysulfones are aromatic PEs made usually by the reaction of bisphenol A and bis (4-chlorophenyl) sulfone in a nucleophilic substitution condensation reaction. The first polysulfones produced by Union Carbide in the early 1960s involved the reaction of bisphenol with and bis(4-chlorophenyl) sulfone in the presence of an alkali base (NaOH, KOH, and K carbonate) in a dipolar aprotic solvent such as NMP, DMSO, sulfolane, or dimethyl acetamide [78], Typical temperatures are in the range of 130-160 °C. The reaction of the base with bis A generates water, which must be removed. 

ABSTRACT. Toluene radical anion, generated by dissolving potasssium metal in toluene by the assistance of dicyclohexano-18-crown-6, has been proved to be especially effective for reductive removal of fluorine atom from unactivated alkyl fluorides that resist common reduction conditions. Stereochemical and mechanistic aspects of the present method is discussed. In connection with the preparation of substrates the effect of dipolar aprotic solvents on the nucleophilic fluorination with potassium fluoride/dicyclohexano-18-crown-6 system was also examined, and sulfolane or N,N-dimethylformamide was shown to be a solvent of choice. 

Examination of Solvent Effect on Nucleophilic Fluorination with KF/ dicvclohexano-18 crown-6. Using 1-bromodocosane (12) as substrate and KF/DC-18-C-6 as reagent system, solvent effect was examined. Solvents were chosen from common dipolar aprotic solvent [acetonitrile, hexa-methylphosphoric triamide (HMPT), dimethylsulfoxide (DMSO), diglyme], from weakly basic dipolar aprot c solvents (sulfolane, ethylene carbonate, propylene carbonate) " and from acid amide solvents [N,N-dimethylformamide (DMF), N,N-diethylacetamide (DEA), N-methyl-pyrrolidone (NMP), tetramethylurea]. ... 

Factors Involved include (1) the reactivity of monomers, (2) the solvating power of the solvent, which may enhance [1], [3] the temperature necessary to achieve useful molecular weight in a reasonable time [4] the solubility of the high molecular weight polymer under the reaction conditions, and [5] the choice of base, either carbonate or hydroxide. Among the dipolar aprotic solvents most frequently used are dimethyl sulfoxide, dimethyl acetamide, N-methylpyrrolidinone (NMP), sulfolane (tetramethylene sulfone), dimethyl sulfone, and diphenyl sulfone. 

Dipolar aprotic organic solvents, e.g., acetonitrile, tetrahydrofurane, dimethylformamide, dimethylsulfoxide, sulfolane, methylene chloride, y-butyrolactonc, etc ... 

HP he study of the behavior of electrolytes in mixed solvents is currently arousing considerable interest because of its practical and fundamental implications (1). Among the simpler binary solvent mixtures, those where water is one component are obviously of primary importance. We have recently compared the effects of small quantities of water on the thermodynamic properties of selected 1 1 electrolytes in sulfolane, acetonitrile, propylene carbonate, and dimethylsulfoxide (DMSO). These four compounds belong to the dipolar aprotic (DPA) class of solvents that has received a great deal of attention (2) because of their wide use as media for physical separations and chemical and electrochemical reactions. We interpreted our vapor pressure, calorimetry, and NMR results in terms of preferential solvation of small cations and anions by water and obtained... 

It is well known that alkali and alkaline earth cations are very difficult to complex due to the configuration of the rare gas electronic structure of these ions. Fortunately, some specific ligands are known, such as aprotic dipolar solvents (dimethylformamide, sulfolane, dimethylsulfoxide, N-methyl pyrolidone and so on), aminoxides, phosphinoxides, glymes and polyethylene glycols, crown ethers and cryptates, bidentate amines (tetramethyl ethylene diamine, 1,10 phenanthroline, etc. [14, 53, 61, 68]. 

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