Solvents 1,1,1,3,3,3-hexafluoro-2-propanol

Good solvent 1,1,1,3,3,3-hexafluoro-2-propanol, chloroform/1,1,1,3,3,3-hexafluoro-2-propanol ... 

Thus, the quite different solvent properties, e.g., from hexafluoro-propanol (1) to butyl alcohol (11), are not reflected in their anion-solvent interatomic distances. This finding contradicts the generally observed fact that stronger interactions lead to shorter distances. 

Step A (eq 1)—the disulfide bond formation between a peptide fragment derivatized at the C-terminus as 6-mercapto-dibenzofuranyl ester and a peptide fragment bearing an 5 sulfenylthiocarbonate (Scm) activated cysteine residue at its N-terminus, occurs cleanly and very rapidly at submillimolar concentrations in protic solvents or solvent mixtures. The intramolecular acyl transfer (step B, eq 1) is highly efficient (effective molarity > 1 M), to the effect that, for most cases, a very weakly activated phenolic ester can be employed and many quite reactive side-chain functions in R and R can be left unprotected. These high reactivity criteria are met best in the protein-solubUizing solvent hexafluoro-2-propanol (HFIP) and its mixtures with water and acetonitrile. ... 

The polymers dissolve in l,l,l,3,3,3-hexafluoro-2-propanol [920-66-1/, hot phenols, and /V, /V- dim ethyl form am i de [68-12-2] near its boiling point. The excellent solvent resistance notwithstanding, solvents suitable for measurement of intrinsic viscosity, useflil for estimation of molecular weight, are known (13,15). 

Hexafluoro-2-phenyl-2-propanol may be recovered from mother liquors, recovered solvent, and the KBr salt cake by extracting the mixture with aqueous base. Neutralization of the aqueous phase gives the alcohol (13-23 g.) which is purified by distillation. 

Furthermore, the stereochemistry of the product 1 changes as the solvent is changed. In aqueous dioxane, the reaction proceeds with complete inversion, but in 1,1,1,3,3,3 hexafluoro-2-propanol with 100% retention. In acetic acid, the reaction occurs mainly with inversion (83%), but in formic acid the amount of retention (40%) is comparable to the amount of inversion (60%). Discuss these results, particularly with respect to the change of product composition and stereochemistry as a function of solvent. 

Controlling for these forces requires variation in the amount of salt, organic solvent, and the pFI of the mobile phase. It is impractical to perform such experiments with 50 mM formic acid an alternative additive must be used that maintains its chaotropic properties independent of salt content or pFI. Fortunately, mobile phases containing 50 mM hexafluoro-2-propanol (HFIP) afford a fractionation range comparable to that of the formic acid (Fig. 8.6), permitting the effects of these variables to be studied systematically. 

In some cases, these organic solvents cause no stronger folding but adversely (Lys-Gly-Pro)n folds to a lower extent in l,l,l,3,3,3-hexafluoro-2-propanol/ethylene glycol or in 1,3-propandiol than in water (Table 3). 

Kwon and coworkers prepared a series of nano- to microstmctured biodegradable PCLA porous fabrics by electrospinning. The nanoscale-fiber porous fabrics were electrospun with PCLA (1 1 mole ratio, approximately 0.3-1.2 mm in diameter) using l,l,l,3,3,3-hexafluoro-2-propanol as a solvent. 

Hexafluoro-wo-propanol has become a popular solvent. Its fluorine, proton, and carbon spectra are provided in Figs. 6.15-6.17. The doublet in the fluorine spectrum centered at -77.1 ppm exhibits a three-bond... 

In the solvolysis of secondary alkyl sulfonates, competition between nucleophilic solvation and electron donation by the substituents results in a significantly solvent-dependent p, which varies from — 9 to — 1 on going from the non-nucleophilic hexafluoro-2-propanol to 80% aqueous ethanol (Bentley et al, 1981). In contrast, the p -invariance for alkene bromination in H20, M70, MeOH and AcOH [equations (22)-(25)] seems to imply a perfect balance between the two types of charge stabilization. However, this conclusion is probably risky since the nucleophilicities of the solvents implied in (22)-(25) do not vary markedly. Data in non-nucleophilic fluorinated solvents would therefore help to fill the gap in our knowledge. 

As a result, the plots of o- / vs. E for different bulk concentrations of the solute intersect at the same point (Umax. max). which corresponds to the adsorption maximum. This implies that at the adsorption maximum does not vary with increasing F. Consequently, the surface dipole potential due to the adsorbing molecules exactly matches that of the desorbed solvent molecules, " provided that the solvent and solute molecules assume only one orientation at the surface. In practice, however, a single point of intersection of the vs. E plot for different bulk solute concentrations is observed rather rarely. For example, a gradual inaease in the surface concentration of 2-propanol on mercury in aqueous solution brings about a small positive shift of a. A much bigger shift has been observed for hexafluoro-2-propanol (HFP). " It has been ascribed to the reorientation of the HFP molecules in such a way that both -CF3 groups are directed toward the electrode, which in turn results in... 

As a third example for an organocatalytic reaction, based on multiple hydrogen bonding and mechanistically investigated by DFT, we selected olefin epoxidation with hydrogen peroxide in fluorinated alcohol solvents, such as 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) (Scheme 3.8). Here we encounter a new type of catalytic hydrogen bond the cooperative hydrogen bond. 

In 1998, Begue and coworkers reported on a very selective conversion of sulfides to sulfoxides in hexafluoro-2-propanol (HFIP) as solvent using 30% H2O2 as oxidant without the need for a catalyst (equation 54) . A variety of differently substituted acyclic sulfides and also a cyclic one could be cleanly oxidized to the sulfoxides in very good yields ranging from 82 to 99% and no sulfone formation was observed. C=C double bonds in the substrate are tolerated without being epoxidized. This excellent reactivity is explained... 

Fluorous solvents proved to be highly effective in epoxidation of alkenes. H202 can be used in combination with trifluoroacetone,27 perfluoroacetone,28 or a mixture of perfluoroacetone and hexafluoro-2-propanol.29 In fluorinated alcohols as solvents uncatalyzed epoxidations with aqueous H202 are performed.30,31... 

Zhao, C.H., Yao, J.M., Masuda, H., Kishore, R., and Asakura, T. "Structural characterization and artificial fiber formation of Bombyx mori silk fibroin in hexafluoro-iso-propanol solvent system". Biopolymers 69(2), 253-259 (2003). 

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