Acetone aprotic, polar

Another set of papers is due to Mancini and coworkers111-113. In mixtures of acetonitrile or nitromethane with ethyl acetate, 2-butanone, acetone, DMF and DMSO, the differences between the results for 2 and 5 were much smaller (<0.04) than noted above over the entire composition ranges, hence their averaged n values appear to be measures of the polarity/polarizability of the mixtures rather than probe-dependent quantities. The same appears to be the case for the EPD/HBA properties measured by the 2/1 and 8/5 probe pairs of mixtures of acetonitrile with ethyl acetate, DMF and DMSO, but not for acetonitrile-rich mixtures with DMF or DMSO, where the differences between the two probe pairs are considerable111. Mixtures of aprotic polar solvents with chloroform showed discrepancies of the results for 2 and 5 of up to 0.15 units, whereas for such mixtures with dichloromethane the differences were smaller, up to 0.05 units in ji. The 2/1 and 8/5 probe pairs for EPD/HBA properties of these mixtures showed differences for both chloroform and dichloromethane mixed with ethyl acetate, acetonitrile and DMSO, precluding the estimation of reliable ft values111. The results with HBD solvent components were interpreted in terms of specific interactions with the probes113. 

Aprotic polar solvents thus far employed in metal-catalyzed polymerizations include dimethoxybenzene (DMB), diphenyl ether (DPE), ethylene carbonate, acetonitrile, /V, /V-d imethylformamid e (DMF), and acetone, among others. Most of them are employed for copper catalysts because of their low solubility. For well-solubilized Ru(II), Ni(II), and Fe(II) complexes with phosphine or other ligands, such an additional precaution is not necessary, and toluene or other relatively nonpolar solvents have mostly been used. 

Aprotic solvents do not contain —OH groups and cannot function as hydrogen-bond donors. They are unable to promote the formation of a carbocation because the leaving group would be unsolvated. Therefore aprotic solvents cannot be used in Sfjl reactions. Table 7.4 lists the aprotic solvents most commonly used for nucleophilic substitution reactions. Dimethyl sulfoxide and acetone are polar aprotic solvents dichloromethane and diethyl ether are less polar aprotic solvents. The aprotic solvents listed in the table are particularly good ones in which to carry out 8 2 reactions. Because polar aprotic solvents are able to solvate only cations and not anions, they allow for naked and highly reactive anions as nucleophiles when used with ionic nucleophiles such as Na+CN , Na+OH , and so on. 

Bromine ion is a good leaving group on a 2° carbon. The methylsulfide ion is a good nucleophile. Acetone, a polar aprotic solvent, is a good medium in which to carry out 8 2 reactions, but a poor medium in which to carry out Sfjl reactions. We predict that reaction is by an Sfj2 mechanism and that the product formed has the R configuration. 

Aprotic-polar Ketone Acetone Methyl isobutyl ketone... 

Intravascular catheter is used for providing central venous nutrition and performing dialysis treatment. Antimicrobial layers may be formed with an antimicrobial agent such as antibiotic coated on the surface. The antimicrobial agent may be continually released from the surface while inside the body. Most antibiotics are very polar and do not dissolve in organic solvents. Aprotic polar solvents, such as dimethylformamide, dimethyl sulfoxide, dimethylacetamide, 2-butanone, acetone, acetinitrile, and N-metiiylpyrrolidone are useful in this application. ... 

Aprotic means that the solvent does not have a proton on an electronegative atom. The solvent can still have hydrogen atoms, but none of them are connected to electronegative atoms. The most common examples of polar aprotic solvents are acetone, DMSO, DME, and DMF ... 

Especially for large-scale work, esters may be more safely and efficiently prepared by reaction of carboxylate salts with alkyl halides or tosylates. Carboxylate anions are not very reactive nucleophiles so the best results are obtained in polar aprotic solvents45 or with crown ether catalysts.46 The reactivity order for carboxylate salts is Na+ < K+ < Rb+ < Cs+. Cesium carboxylates are especially useful in polar aprotic solvents. The enhanced reactivity of the cesium salts is due to both high solubility and minimal ion pairing with the anion 47 Acetone is a good solvent for reaction of carboxylate anions with alkyl iodides48 Cesium fluoride in DMF is another useful... 

A term, usually referring to a solvent, describing a compound which act neither as a proton donor nor a proton acceptor. Examples of polar aprotic solvents include dimethylformamide, dimethylsulfoxide, acetone, acetonitrile, sulfur dioxide, and hexamethylphosphoramide. Examples of nonpolar aprotic solvents include benzene and carbon tetrachloride. Studies of reactions in protic and aprotic solvents have demonstrated the importance of solvation on reactants, leaving groups, and transition states. Degrees of nucleophilicity as well as acidity are different in aprotic solvents. For example, small, negatively charged nucleophiles react more readily in polar aprotic solvents. It should also be noted that extremely... 

The assistance of the solvent molecule was later confirmed experimentally the reaction rate decreased significantly when changing a polar protic solvent such as ethanol by a polar aprotic solvent such as acetone (see left part of Fig. 3). This was a good example showing how computational calculations can be useful not only rationalizing experimental observations but also having predictive power. 

The H NMR spectra of organic compounds are usually obtained in an aprotic solvent at concentration levels of a few percent. The most widely used solvent is deuterated chloroform (CDC13), sufficiently polar to dissolve most organic compounds. Acetone-r/6 (C3D60), methanol-e 4 (CD3OD), pyridinc-r/5 (C5D5N) and heavy water (D20) are also used. 

This behaviour is that expected if the positive effect of the dipolar aprotic solvent on the activity of the hydroxide ion is superimposed on the normal negative effect of an organic solvent, and should be observed also for other dipolar aprotic solvents. In fact this type of behaviour is found for the alkaline hydrolysis of ethyl p-nitrobenzoate in mixtures of water and acetone, which is less polar than dimethyl sulphoxide. Other esters show intermediate behaviour in this solvent259 (Fig. 16). It should be stressed that this represents special... 

Peach et al. developed a general, racemization free, and high yield procedure for the synthesis of O-desyl peptide esters from the poorly nucleophilic benzoin.1261 Employing the cesium salt of the model dipeptide Z-Gly-Phe-OH in acetone the intramolecular hydantoin formation obtained in polar aprotic solvents, such as DMF and DMSO, can be suppressed and a high yield of Z-Gly-Phe-O-desyl with ee >90% can be generated. 261 ... 

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... 

With regard to SN2 reactions, the solvent can affect profoundly the reactivity of a given nucleophile. Thus anions such as Cl and CNe, which are weakly nucleophilic in hydroxylic solvents and in poor ionizing solvents such as 2-propanone (acetone), become very significantly nucleophilic in polar aprotic solvents such as (CH3)2SO. The reason is that for salts such as NaCl and NaCN the aprotic solvent preferentially solvates the cation, leaving the anion relatively bare. This dissociation of the anion from the cation together with its poor solvation makes the anion abnormally reactive as a nucleophile. 

The Kolbe Nitrile Synthesis is a typical SN2 reaction, which runs best in polar aprotic solvents (DMSO, acetone) ... 

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