Aprotic chloroform

Aluminum chloride dissolves readily in chlorinated solvents such as chloroform, methylene chloride, and carbon tetrachloride. In polar aprotic solvents, such as acetonitrile, ethyl ether, anisole, nitromethane, and nitrobenzene, it dissolves forming a complex with the solvent. The catalytic activity of aluminum chloride is moderated by these complexes. Anhydrous aluminum chloride reacts vigorously with most protic solvents, such as water and alcohols. The ability to catalyze alkylation reactions is lost by complexing aluminum chloride with these protic solvents. However, small amounts of these "procatalysts" can promote the formation of catalyticaHy active aluminum chloride complexes. 

We have investigated the bromo-addition of alkenes and their related compounds with BTMA Br3. Thus, we found that the reaction of alkenes with BTMA Br3 in aprotic solvents such as dichloromethane and chloroform gave 1,2-dibromo adducts in a manner of stereospecific anti-addition, and, in such protic solvents as methanol and acetic acid, gave the corresponding dibromo adducts along with considerable amounts of solvent-incorporated products in regioselective manner (Fig. 18) (ref. 29). 

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. 

In another smdy, the introduction of an adamantyl group to the poly(etherimide) structure caused polymer glass transition temperature, Tg, and solubility enhancements in some solvents like chloroform and other aprotic solvents [92]. 

Like the carbodiimide method, the mixed anhydride method results in an amide complex (Table 5, Figure 17). The acid-containing hapten is dissolved in a dry, inert, dipolar, aprotic solvent such as p-dioxane, and isobutyl chloroformate is added with an amine catalyst. The activated mixed anhydride is chemically stable and can be isolated and characterized. The aqueous protein solution is added to the activated acid and the pH is maintained at around 8.5. A low temperature (around 10 °C) is necessary during the reaction to minimize side reactions. 

Aprotic solvents are not protogenic, but can be protophilic, e.g. acetone, 1,4-dioxan, tetrahy drof uran, dimethy If ormamide, hexamethylphos-phortriamide, propylene carbonate and sulpholane. Solvents that do not participate in protolytic reactions, i.e. do not donate or accept a proton, are usually chemically inert, such as benzene, chlorobenzene, chloroform, tetrachloromethane, etc. 

This preparation is carried out in an aprotic solvent (e.g. benzene, chloroform) with no special provision other than working in a well-ventilated fume hood to avoid ill-smelling sulfur compounds. Various ligands have proved successful phosphines, pyridines, imidazoles, tetra-m ethyl thiourea, etc. When the same reaction is carried out in the absence of the Lewis base L, a dimer 6 is obtained, which is a useful catalyst in its own right and sometimes a much more active one see Section VILA. The chemical equation for that reaction is,... 

Poly(ether ketone)s 3, 4, 5, 6, and 7 were soluble in polar aprotic solvents such as DMAc and NMP and in chlorinated solvents such as chloroform. The improved solubility of these fluorinated poly(ether ketone)s can be explained by the presence of both the flexible hexafluoroisopropylidene groups and the bulky 1,4-naphthalene moieties, which inhibit polymer crystallization and facilitate the penetration of solvent molecules between the polymer chains. 

Four poly(ether ketone)s obtained from 2,2-bis[4-(4-fluorobenzoyl)-phenyl]-1,1,1,3,3,3-hexafluoropropane (9) or 2,2-bis[4-(4-fluorobenzoyl)-phenyl]propane (10) with Bisphenol AF (1) or Bisphenol A (4) are all soluble in chloroform, benzene, THF, and aprotic polar solvents such as DMF, DMAc, and NMP.15 Poly(ether ketone) from 9 and 1, which has the highest fluorine content, dissolves easily in ethyl acetate. 

Considering nitration with the help of NO2/N2O4 in an aprotic medium, one should avoid a simplified approach to its mechanism. The dissociation equilibrium N2O4 = 2NO2 is characterized at 298.15 K (25°C) with constants, on molality basis, 3.5 X 10 in hexane, 5.9 X 10 in carbon tetrachloride, and 5.3 X 10 in chloroform (Mendiara and Perissinotti 2003). In aprotic mediums, two ionic routes of dissociation of N2O4 are possible... 

Solutions of dinitrogen pentoxide in aprotic solvents like methylene chloride, chloroform and carbon tetrachloride are efficient reagents for the iV-nitration of secondary amines. These reactions, known as nucleophilic nitrations , need excess amine present to react with the nitric acid formed during the reaction. Such nitrations are useful for the synthesis of secondary... 

In aprotic solvents, the carbanions, generated by reduction of carbon tetrachloride or ethyl trichloroacetate at mercury, can be trapped by reaction with an added carbonyl compound [74], This reaction has been developed as a useful step in synthesis. Cathodic reduction of a system containing a catalytic amount of carbon tetrachloride, excess chloroform and an aldehyde leads to an effective ionic chain reaction sustained by trichlormethyl carbanions as indicated in Scheme 4.4. A carbon-felt cathode is used with diraethylformamide as solvent [75]. Aldehydes react with cuiTent efficiency of 700 %, which indicates a short chain reaction. Ketones... 

Thus, N-pyrimidine phthalimide reacted with hexylamine at room temperature to form an amide-amide. The initial amide-amide formation proceeded more rapidly in chloroform as compared to dimethylsulfoxide (DM SO). However, the ring closure reaction to the imide was favored by the more polar, aprotic DMSO solvent, yielding the imide in nearly quantitative yield after 3 hours at 75 °C. The authors were able to utilize this synthetic approach to prepare well-defined segmented poly(imide-siloxane) block copolymers. It appears that transimidi-zation reactions are a viable approach to preparing polyimides, given that the final polyimide has a Tg sufficiently low to allow extended excursions above the Tg to facilitate reaction without thermal decomposition. Additionally, soluble polyimides can be readily prepared by this approach. Ultimately, high Tg, insoluble polyimides are still only accessable via traditional soluble precursor routes. 

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. 

Because of its insolubility in common aprotic solvents, iodosylbenzene is of limited use for uncatalyzed oxidations in such media. The o-tert-butylsulfonyl derivative 6 of iodosylbenzene, on the other hand, is moderately soluble (0.08 M) in chloroform and has been employed for uncatalyzed oxidations of sulfides and phosphines to sulfoxides and phosphine oxides (Scheme 3) [17]. 

On the other side of the scale, very moderate, but not negligible, Lewis acidities are ascribed, according to their a parameters, to C-H acids, such as chloroform and bromoform, primary and secondary acyclic amines, such as -butylamine and diethylamine, and protogenic solvents, such as methyl-alkyl ketones, acetonitrile, and nitromethane. It can be expected that liquid 1 -alkynes (not on the List), having the grouping H-C=C-R, also have non-negligible a values, being C-H Lewis acids. It can be safely concluded, however, that aprotic solvents other than those of the classes noted above have no Lewis acid character, with a 0 for all intents and purposes. 

Rates of decomposition do not vary much with the halide ion. The reactivity order falls between that which is usally observed in the gas phase or in aprotic media (Cl>Br>I) and that which is observed in hydroxylic solvents (Clfirst-order decomposition may occur in more ionizing media, for example CD3CN or PhNC>2, in which dissociation leads to the incursion of a second-order component. 

The self-assembling cyclic D,L-cc-peptide nanotubes described demonstrate high stability on surfaces even after two months exposure to ambient temperature. NDI peptide nanotubes 18 may provide a facile method for the preparation of a new class of synthetic biomaterials [16b, 34a]. Recently Sanders and co-workers demonstrated the formation of amino acid-derived NDI hydrogen-bonded supramo-lecular organic M-helical nanotubes in nonpolar solvents and also in the solid state [34b]. The hydrogen-bonded supramolecular nature of the helical nanotubes was confirmed by the circular dichroism (CD) spectrum in chloroform with the addition of methanol, destruction of the supramolecular nanotubes was observed, due to the capabilities of such an aprotic solvent to compete for hydrogen-bond interactions [34b]. 

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