Solvent admixture

In individual cases, it is expedient to perform the interaction of a donor and an acceptor in gaseous phase by means of joint vacuum sublimation of the components. Such a method was employed in the case of (TTT)(TCNQ)2. In this example, solvent admixtures are absolutely absent in the conductive material. 

In the absence of a moderating solvent, admixture of DMSO and trifluoroacetic anhydride proceeds explosively. ... 

Synthesis by high-dilution techniques requires slow admixture of reagents ( 8-24 hrs) or very large volumes of solvents 100 1/mmol). Fast reactions can also be carried out in suitable flow cells (J.L. Dye, 1973). High dilution conditions have been used in the dilactam formation from l,8-diamino-3,6-dioxaoctane and 3,6-dioxaoctanedioyl dichloride in benzene. The amide groups were reduced with lithium aluminum hydride, and a second cyclization with the same dichloride was then carried out. The new bicyclic compound was reduced with diborane. This ligand envelops metal ions completely and is therefore called a cryptand (B. Dietrich, 1969). 

Almost all of the cyclohexane that is produced in concentrated form is used as a raw material in the first step of nylon-6 and nylon-6,6 manufacture. Cyclohexane also is an excellent solvent for cellulose ethers, resins, waxes (qv), fats, oils, bitumen, and mbber (see Cellulose ethers Resins, natural Fats AND FATTY OILS Rubber, NATURAL). When used as a solvent, it usually is in admixture with other hydrocarbons. However, a small amount is used as a reaction diluent in polymer processes. 

Suitable organic solvents, such as ether, benzene, naphtha and the like, are more soluble than in water. This makes it possible to separate them from other substances which may accompany them in the water solution but which are not soluble in the solvents employed. Hence, one application of solvent extraction is the analytical determination of unsaponifiable oils and waxes in admixture with fatty material by submitting the mixture to vigorous saponification with alcoholic potash or, if necessary, sodium ethylate, and to dilute the product with water and extract with petroleum ether. The soaps remain in the aqueous solution while the unsaponifiable oils and waxes dissolved in the ether. The addition of a salt to an aqueous solution prior to extraction is sometimes practiced in some processes. In older processes, SOj is employed in the separation of aromatic and highly saturated hydrocarbons, taking advantage of the much greater solubility of the solubility of the aromatics and... 

D 2251 1985 Test method for metal corrosion by halo-genated organic solvents and their admixtures... 

Apart from these typical acid-catalyzed reactions, the method is capable of dealing with bimolecular processes, and even reactions that are not acid-catalyzed. For any process that takes place in non-ideal aqueous acid media, it should be the first technique tried. Admixture of the aqueous acid with moderate amounts of inert organic solvent should not be a problem. The broad variety of reaction mechanisms given above should display the versatility and utility of the excess acidity method in physical organic chemistry. 

An admixture of 16b and 17b self-assembles quantitatively at millimolar concentration in chloroform solution to produce an inclusion complex whose absorption and emission maxima are red-shifted by 40 nm [56]. Clicking both ends of this pseudorotaxane with two molar equivalents of stopper S2 produces the squaraine rotaxane 16b D 19b in near-quantitative yield [58]. Pseudorotaxane 16b D 17b partially dissociates at micromolar concentrations in chloroform and produces two emission peaks, one at 638 nm which corresponds to free squaraine 17b and one at 694 nm, corresponding to the pseudorotaxane. In contrast, the squaraine rotaxane 16b D 19b does not dissociate under these conditions or in more polar solvents such as pure methanol. 

It has also been shown [254] that a commercial petroleum sulfonate surfactant which consists of a diverse admixture of monomers does not exhibit behavior typically associated with micelle formation (i.e., a sharp inflection of solvent properties as the concentration of surfactant reaches CMC). These surfactants exhibit gradual change in solvent behavior with added surfactant. This gradual solubility enhancement indicates that micelle formation is a gradual process instead of a single event (i. e., CMC does not exist as a unique point, rather it is a continuous function of molecular properties). This type of surfactant can represent humic material in water, and may indicate that DHS form molecular aggregates in solution, which comprise an important third phase in the aqueous environment. This phase can affect an increase in the apparent solubility of very hydrophobic chemicals. 

Rappoport and co-workers work has continued in a study of the substitution of ( )-and (Z)-/3-bromo- or chloro-styrenes, (1) and (2), by MeS in DMSO-d 6 (sometimes in admixture with CD3OD) as solvent. Product studies indicated retention stereochemistry rate measurements found only a small Br/Cl element effect, slower reactions of the p-OMe bromo compounds, and retardation by CD3OD. These results are consistent with Tiecco s suggestion in 1983 that even this system, activated by only a single phenyl group, reacts through the nucleophilic addition-elimination multistep route. 

Proton-containing admixtures in a solvent or in benzaldehyde can act like water. The superoxide ion abstracts such labile proton and generates the HOO base. The base in its turn abstracts proton from a solvent, for example, AN. If benzaldehyde is present, it is converted into cinnamyl nitrile according to the following simple reactions ... 

The physical properties of crystals depend on admixtures this is common knowledge. The admixtures can be present in a starting solution. Solvent molecules included in a crystal during its formation should be considered a contamination. In this sense, the highest attention should be... 

Minor admixtures of water to nonaqueous electrolytes are often harmful, for example in batteries with inorganic solvents such as POCI3, SOCI2, SO2CI2, where it is important that the electrolyte be free of water contamination because of the possible formation of oxychloride cements ... 

The popular weak solvents, which promote polymer adsorption are cyclohexane, dichloro methane, dichloroethane and toluene. Unfortunately, any standardization of the eluent purity/content of admixtures does not exist. This might be one of reasons why it is sometimes difficult to maintain long-term repeatability and interlaboratory reproducibility of measurements in polymer HPLC. 

The most serious obstacle for the free radical nature of triphenylmethyl was the series of experiments carried out to determine the molecular weight of triphenylmethyl . Cryoscopy was performed in a range of solvents and invariably showed that the molecular weight corresponded to that of the dimer, 486. Only in naphthalene, which in admixture with triphenylmethyl froze at about 80°C, was a lower value obtained, 410. This was a serious dilemma, but Gomberg in 1904 had a reasonable suggestion involving an equilibrium between a dimer and the free triphenylmethyl. 

Reducing agents, such as hydroquinone, Br , I, SCN- ions, and others, are used as supersensitizers for electron photoinjection reactions. Figure 28 illustrates how an admixture of hydroquinone affects photocurrent in the system CdS—rhodamine B. In certain cases the solvent, water, can also act as a supersensitizer. For example, if the bipyridyl complex of Ru(II) is a sensitizer, the oxidized form, the complex of Ru(III), can oxidize water to oxygen... 

W. Steubing found that the intensity of the fluorescence of iodine vapour is weakened between the poles of a powerful electromagnet. The result has nothing to do with the Zeeman effect, and has no connection with effects produced by admixture with gases, solvents, etc. It is produced by a direct action of the magnetic field on the electrons causing the band spectrum weakening the individual vibrations. 

Smokeless propellants may be taken as another example of composite explosives. These may be either mixtures of nitrocellulose of differing degrees of nitration, partly in a colloidal and partly in a fibrous state with an admixture of the remaining solvent and a stabilizer or a solution of nitrocelluloses in carbamite (centralite) and nitroglycerine with an admixture of components such as aromatic nitro compounds, nitroguanidine, graphite etc. 

Acetal is a poor solvent for NC but its admixture with anhydrous alcohoI(see Acetal Solvent) greatly increases its solvent power (Ref 8)... 

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