2,2,2-Trifluoroethanol solvent

Under some conditions the secondary reactions can be suppressed, and the concentrations of primary products then increase linearly as the reaction proceeds. For example, Fig. 3 gives the results of a reaction in which the homologation process has been inhibited by added tri-w-butylphosphine. A similar inhibition of the homologation reaction was found in experiments carried out in 2,2,2-trifluoroethanol solvent (36). This alcohol is itself resistant to homologation under these conditions, but does undergo transesterification with methyl formate. 

Tetrahydrofurfuryl alcohol 2,2,2-Trifluoroethanol solvent, occlusive Wheat (Triticum vulgare) germ oil solvent, occlusive make up Cocoa (Theobroma cacao) butter solvent, occlusive ointments Walnut (Juglans regia) oil solvent, occlusive OTC pharmaceuticals Cocoa (Theobroma cacao) butter solvent, occlusive pharmaceutical topicals Walnut (Juglans regia) oil solvent, occlusive sun preps. 

Although the a/s ratio in Equation 120 is smaller than desired for a property used in constructing the a scale, it was included because it allowed independent confirmation of a for trifluoroethanol (solvent 113) and hexafluoroisopropanol (114), whose other a,s were all based on the C-nmr spectrum of phenyl methyl sulfoxide. 

Difluoroethanol [359-13-7], F2CHCH2OH, is a colorless Hquid with an alcohol-like odor mp, 28.2°C, bp, 96°C d[, 1.3084 n], 1.3320 heat of combustion, —1026 kJ/mol(—245.3 kcal/mol). It is stable to distillation and miscible with water and many organic solvents. As expected, its acidity Hes between that of 2-fluoroethanol and 2,2,2-trifluoroethanol both ia the gas phase (25) and ia 50% aqueous ethanol solution (26), where its of 1.0 x 10 is about 4.8 times smaller than that of trifluoroethanol. 

The configurations of chiral thiiranes and thiirane 1-oxides can be determined by H NMR experiments in chiral solvents such as (R)-(-)- -phenyl-2,2,2-trifluoroethanol. The... 

Stabilization of a carbocation intermediate by benzylic conjugation, as in the 1-phenylethyl system shown in entry 8, leads to substitution with diminished stereosped-ficity. A thorough analysis of stereochemical, kinetic, and isotope effect data on solvolysis reactions of 1-phenylethyl chloride has been carried out. The system has been analyzed in terms of the fate of the intimate ion-pair and solvent-separated ion-pair intermediates. From this analysis, it has been estimated that for every 100 molecules of 1-phenylethyl chloride that undergo ionization to an intimate ion pair (in trifluoroethanol), 80 return to starting material of retained configuration, 7 return to inverted starting material, and 13 go on to the solvent-separated ion pair. 

Reactions of substituted cumyl benzoates in 50 50 trifluoroethanol-water show no effect of [NaN3] on the rate between 0 and 0.5 M. The product ratio, however, is highly dependent on the cumyl substituent. Electron-releasing substituents favor azide formation whereas electron-withdrawing substituents result in solvent capture. Formu-... 

Trifluoromethyl-l-phenylethyl tosylate has been used to differentiate as shown in Table 1, the solvolytic power of three fluorinated solvents and to compare these with formic and acetic acids The three fluorinated solvents are trifluoroacetic acid, trifluoroethanol, and 1,1,1,3,3,3-hexafluoroisopropyl alcohol [55]... 

Generation of phenylnitrcne by thermal decomposition of phenyl azide in the same solvent mixture, or by deoxygenation of nitrosobenzene with triethyl phosphite in the absence of the trifluoroethanol, fails to yield the 1//-azepine. The role of the alcohol in promoting l//-azepine formation is not understood. 

The sequence Gly-Glu-Arg... folds better in water than in methanol as shown below. Many folding investigations have shown clearly different influences of the solvents. Even in many cases, folding can be enhanced in methanol, or methanol/water mixtures, trifluoroethanol, buffer solutions, or higher concentrated salt solutions. 

The 15N content was indeed lower when the experiment was performed This result justified the publication of a preliminary communication (Bergstrom et al., 1974). Later work (Hashida et al., 1978 Szele and Zollinger, 1978a Maurer et al., 1979) involving sophisticated statistical treatments suggested that, in a weakly nucleophilic solvent such as trifluoroethanol, the phenyl cation is formed in two steps and not in one, as in mechanism B (see Scheme 8-4 in Sec. 8.3), the first intermediate being a tight ion-molecule pair. 

Ijljl-trifluoroethanol (TFE), a solvent with a strong hydrogen-bond donor capacity. This supports the idea that hydrogen-bonding interactions also contribute noticeably to the acceleration of aqueous Diels-Alder reactions. 

A few other successful 13C 1-NMR determinations should be mentioned. Hunt et al. [28] used 13C NMR to characterise fractions of extracted analytes of PAG and sorbitan ester samples and identified Irganox 1010. H and 13C NMR have been used to identify the main organic components of a breathable diaper back-sheet as LLDPE and pentaerythritol tetra-octyl ester (PETO) [233]. The equally present AOs Irganox 1010 and Irgafos 168 were not detected without extraction. Barendswaard et al. [234] have reported fully assigned 13C solution spectra of these two antioxidants. Chimas-sorb 944 in a polyamide matrix can be determined by H or 13C 1-NMR using solvents such as formic acid, trifluoroacetic acid or trifluoroethanol [235], Both H and 13C NMR have been used to follow the chemistry of a bis-phenoxidemethylaluminum complex (reaction product of BHT and trimethylaluminum) by exposure in air. Pierre and van Bree [216] also used 13C NMR to... 

A trend emerged in that the best conditions involved either the use of a Lewis acid additive (BF3 OMe2) or a more polar solvent-such as trifluoroethanol (TFE), although the beneficial effect of TFE did depend on the ligand employed [27]. The... 

The use of trifluoroethanol as solvent or absorption of the dienone on silica gel promotes the photoconversion of dienones into bicyclic ketenes.<47) For the photolysis<48 60) of (63) it has been shown by low-temperature infrared and ultraviolet spectroscopy that the initial photolysis gives a ketene which can be efficiently trapped by cyclohexylamine or, in the absence of a good nucleophile, thermally rearranges by a OA, + 20) allowed process to a bicyclic ketone (64) ... 

A major challenge in using interactive chromatography for polyamides is to find a suitable mobile phase (Mengerink et al., 2001, 2002 Weidner et al., 2004). Polyamides form semicrystalline morphologies that limit the solubility in organic solvents. Besides hot phenol, formic acid, and trifluoroethanol (TFE) (Mori and Barth, 1999), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) represents a suitable solvent for polyamides (Chen et al., 2002). These solvents are mainly used to analyze the molar mass distribution of polyamides by SEC. 

A section of the film was dissolved in 3 parts deuterated chloroform (CDCI3) plus 2 parts 1,1,1-trifluoroethanol (IFF), a known good solvent system for... 

The determination of large values of the rate constant ratio ks/kpfrom the low yields of alkene product that forms by partitioning of carbocations in nucleophilic solvents. These rate constant ratios may then be combined with absolute rate constants for the overall decay of the carbocation to give absolute values of kp (s ).14 16 For example, the reaction of the l-(4-methylphenyl)ethyl carbocation in 50/50 (v/v) trifluoroethanol/water gives mainly the solvent adducts and a 0.07% yield of 4-methylstyrene from proton transfer to solvent, which corresponds to kjkp = 1400. This can be combined with ks = 6 x 109 s V4 to give kp = 4.2 x 106 s l (Table 1). 

The partitioning of [1+] between addition of solvent and deprotonation was discussed in Section 2, where it was suggested that the observed ratio of kjkp = 60 in 50/50 (v/v) trifluoroethanol/water underestimates the relative chemical barriers for ks and kp. This is because the addition of solvent is limited by rotational reorganization of solvent, ks = reorg 1011 s-1.21 Use of the larger value of (ks)chem = 1012 s 1 estimated for the addition of solvent that is prepositioned to react with [1+]21 gives kjkp = 600. The latter ratio is close... 

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