Toluene-methanol solutions, effect

An example of equation (101) with X = I and E = HI was found for methanol-DMF solutions both second- and third-order terms were retained . Dvorko s group also found that when X = Cl, a weak nucleophile, the formation of V in equation (100) was slow and subsequent protonation was fast, leading to second-order kinetics (Atj 0) - - when X = I or SCN, the formation of V was often fast and the protonation slow, leading to third-order kinetics (Atj = 0) . Examples of solvent effects superimposed on the basic rate laws are found in Figure 9 , and even more complex effects are found when chlorobenzene, toluene, chlorobenzene-THF mixtures, etc. were used -... 

Dimethoxy-l,4-benzoquinone adds to 3-chloro-l-methoxy-l,3-butadiene in various solvents (Eq. 11). The primary adduct eliminates methanol and aromatizes spontaneously. The reaction is practically quantitative in toluene after 3.5 h of irradiation. An important effect is also observed in methylene chloride solution, where the rate increase reaches a factor of >10. If in this solvent a catalysis by in situ generated hydrogen chloride is possible, another explanation must be found for the sonochemical effect observed in benzene or toluene solution. 

A molecular sieving effect of mesoporous FSM silicas with different pore diameters was reported by Hata et al. [224]. Taxol, an anticancer substance, was not adsorbed in the channels with pore sizes less than 1.6 nm. Taxol contains C=0 and OH groups and was adsorbed only from dichloromethane and toluene solution. It is not adsorbed from methanol or acetone due to the low degree of hydrophilicity of the porous materials. Reaction with trimethyl chlorosilane impeded adsorption because the surfaces are too hydrophobic. By a special adsorption-desorption procedure, Taxol could be enriched from yew needle extracts using certain FSMs. 

CdHgTe quantum dots were synthesised by a rapid injection of CdTe quantum dots in toluene to the methanolic HgBr2 solution at room temperature. TEM revealed the transformation of spherical CdTe (4.5 0.9nm) into wire-like CdHgTe QDs of 3.9 0.8nm diameter. The absorption spectra of the CdHgTe indicated a significant red-shift to 780 nm compared to the parent CdTe QDs (620 nm). The soft nature and the positive redox potential of Hg + ions were influential in the formation of CdHgTe QDs by molecular welding effect. 

Poly(ether sulfone) and poly(ether ketone) rotaxanes 77, 78, 79, and 80 were reported by Xie and Gong via solution polymerization in a mixture of toluene and DMF in the presence of metal ions (K+ or Na+) and 30C10 [114, 123]. The min values depended on the reaction conditions and the amount of BG applied [114, 123]. Polyrotaxanes 77 and 78 were difficult to purify because these polymers formed emulsions in water or methanol. Because of different preparation conditions between those with or without BG, the absolute m/n values are not comparable and thus the effect of the BG on threading remains unknown. However, considering that a polar solvent, i.e., DMF, was used for polymerization, these m/n values are still significant. 

It is likely that some and perhaps all the methanol measured corresponds to the presence of lithium methoxide. This must have some influence on the reaction. Experiments show that it in fact accelerates the polymerization when deliberately added even though it does not initiate polymerization under the conditions used. Even more effective are lithium ethoxide and propoxide which are considerably more soluble in toluene. Lithium methoxide itself is virtually insoluble in toluene, but produced in situ is probably solubilized by association with the active polymer chain ends. Some of it, however, might not be in solution and the possibility of some reaction occurring on the surface of colloidally dispersed salt cannot be excluded. It is interesting to note that both initiators (fiuorenyllithium and butyllithium) which produce a high... 

The first general comment relates to the solvent system. In those cases where the electrolysis substrate does not exist in an aqueous-ethanolic or methanolic solution in a suitable ionic form, it is necessary to provide a solvent system of low electrical resistance which will dissolve the substrate, and also a supporting electrolyte whose function is to carry the current between the electrodes. Examples of such solvents are dioxane, glyme, acetonitrile, dimethylformamide and dimethyl sulphoxide supporting electrolytes include the alkali metal halides and perchlorates, and the alkylammonium salts (e.g. perchlorates, tetrafluoro-borates, toluene-p-sulphonates). With these electrolysis substrates, mass transfer to the electrode surface is effected by efficient stirring. 

Ohashi et al. [128] found that the yields of ortho photoaddition of acrylonitrile and methacrylonitrile to benzene and that of acrylonitrile to toluene are considerable increased when zinc(II) chloride is present in the solution. This was ascribed to increased electron affinity of (meth)acrylonitrile by complex formation with ZnCl2 and it confirmed the occurrence of charge transfer during ortho photocycloaddition. This was further explored by investigating solvent effects on ortho additions of acceptor olefins and donor arenes [136,139], Irradiation of anisole and acrylonitrile in acetonitrile at 254 nm yielded a mixture of stereoisomers of l-methoxy-8-cyanobicyclo[4.2.0]octa-2,4-diene as a major product. A similar reaction occurred in ethyl acetate. However, irradiation of a mixture of anisole and acrylonitrile in methanol under similar conditions gave the substitution products 4-methoxy-a-methylbenzeneacetonitrile (49%) and 2-methoxy-a-methylbenzeneacetonitrile (10%) solely (Scheme 43). 

Also Fryar and Kaufman8 studied the solvent effect on the stability of barium dinonylnaphthalene sulfonate in toluene, toluene/methanol, and methanol solutions by ultracentrifugation and viscometry. The aggregation number of the micelles reduced from about 10 in toluene to about 4 when the mole fraction of free methanol in the solvent mixture was approximately 0.03. In pure methanol BaDNNS micelles did not exist. 

Trace B shows the emission spectrum obtained from a sample of crystals of AuVMeN = COMe)3 after pulsed irradiation, while Trace C shows the spectrum of the light emitted immediately after the addition of chloroform to a previously photo-irradiated sample of Au lMeN = COMe)3 crystals. The spectrum shown in Trace C is that from solvoluminescence. Notice that the emitted light corresponds to the lower energy emission seen for the solid and does not correspond to that seen in solutions of the trimer. Similar emission spectra have been obtained with a number of different solvents including dichloromethane, toluene, methanol, hexane, and even water. In all cases the spectra of the emissions show a maximum at 550 nm. Thus, there is no solvent effect on the emission. However, the intensity of the emission is greatest with those liquids (chloroform, dichloromethane) that are good solvents for the complex and rather feeble in those that are not (hexane, water). 

The effect of the two additives is more evident with the ionic solutes. Nonetheless, the effect of methanol was a slight decrease in all the K values. NaCl Increases the hydrophobic interactions of toluene with the stationary phases. 

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