Trifluoroacetic acid, as a solvent

Katz, J. J. Anhydrous hydrogen fluoride as a solvent for proteins and other biologically important substances. Arch. Biochem. Biophys. 51, 293 (1954) Anhydrous trifluoroacetic acid as a solvent for proteins. Nature 174, 509 (1954) A. L. Koch, W. A. Lamont and J. J. Katz The effect of anhydrous strong acids on ribonuclease and lysozyme. Arch. Biochem. Biophys. 63, 106 (1956). 

Rosbash, D.O. and Leavitt, D., Decalcification of bone with trifluoroacetic acid, Am. J. Clin. Pathol. 22, 914-915, 1952 Katz, J.J., Anhydrous trifluoroacetic acid as a solvent for proteins, Nature 174, 509, 1954 Uphaus, R.A., Grossweiner, L.I., Katz, J.J., and Kopple, K.D., Fluorescence of tryptophan derivatives in trifluoroacetic acid, Science 129, 641-643, 1959 Acharya, A.S., di Donato, A., Manjula, B.N. et al., Influence of trifluoroacetic acid on retention times of histidine-containing tryptic... 

We have recently developed a new and cleaner method for the direct and highly efficient hydrocarboxylation of various C alkanes into the corresponding C , j carboxylic acids [18, 31], It consists in reacting an alkane with CO, H2O, and K2S20g, and in the presence of Cu-catalyst (Scheme 3.5). In contrast to prior alkane carboxylation methods [32, 33], this protocol does not require absolute trifluoroacetic acid as a solvent, and undergoes efficiently at mild temperatures (50-60 °C) and in aqueous acid-solvent-free medium (H20/MeCN mixed solvent), wherein water also plays a main role as a reagent, apart from being a component of the solvent system [18]. 

A detailed investigation of IBX reactions with various vicinal diols revealed that, depending on the substrate and the reaction conditions, either oxidation to a-ketols or a-diketones, or oxidative cleavage of the C—C bond can occur (20070BC767). In DMSO solutions, IBX oxidatively cleaves strained and stericaUy hindered syn 1,2-diols, while the non-hin-dered secondary glycols are oxidized to a-ketols or a-diketones. The use of trifluoroacetic acid as a solvent leads to an efficient oxidative fragmentation of 1,2-diols of aU types (20070BC767). 

Use of trifluoroacetic acid as a co-solvent usually increases the rate of the reaction, but often reduces the yield of products. Acetate anion may accelerate enolization... 

The advantages of trifluoroacetic acid as a very strong organic acid have, of course, been appreciated for a long time they include its unusual properties as a solvent for kinetic... 

Cai et al. [203] prepared a porous scaffold using bacterial cellulose and poly-3-hydroxybutyrate-co-4-hydroxybutyrate (P(3HB-co-4HB)) with a trifluoroacetic acid as a co-solvent, and by freeze-drying the solution to remove the co-solvent. They determined that the scaffold presented a three-dimensional network with improved mechanical properties over P (3HB-co-4HB) alone. 

A solution of trifluoroacetic acid in toluene was found to be advantageous for cydization of pyruvate hydrazoncs having nitro substituents[4]. p-Toluene-sulfonic acid or Amberlyst-15 in toluene has also been found to give excellent results in preparation of indole-2-carboxylale esters from pyruvate hydra-zoiies[5,6J. Acidic zeolite catalysts have been used with xylene as a solvent to convert phenylhydraziiies and ketones to indoles both in one-flask procedures and in a flow-through reactor[7]. 

Trifluoroacetic acid has been examined as a solvent and chlorination of benzene in this is first-order in aromatic and chlorine, but for benzene a higher activation energy (11.4, determined from data at 25.0 and 45.4 °C) was obtained than for chlorination in carbon tetrachloride this unexpected result was attributed to an increase in desolvation energy of the reactants273. 

The chemical oxidation of cis or trans stilbenes was also investigated (Vinogradov et al. 1976). The oxidants were cobalt or manganese acetates, and, in separate experiments, thallium trifluoroacetate. Acetic or trifluoroacetic acid was used as a solvent. The results of such chemical oxidation were considered from the standpoint of the geometry of the recovered (nonreacted) part of the initial substrate and of the stereoisomeric composition of... 

The use of trifluoroacetic acid as both a protonat-ing agent and a solvent frequently allows classification of amines as primary, secondary, or tertiary. This is illustrated in Table 3.4 in which the number of protons on nitrogen determines the multiplicity of the methylene... 

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