On the mechanism of C2F5I photolysis in the presence of trifluoroacetic acid

The photolysis of C₂F₅I with CF₃COOH in the temperature range 473–533 K was studied in the gas phase. Evidence is presented that supports a complex mechanism for the formation of C₂F₅H through the H-atom abstraction reaction from CF₃COOH by C₂F₅ radicals as well as the participation of I(²P_½).     

High-temperature transnitrilation of 2-bromocaproic acid

Chromato-mass spectrometry and IR and PMR spectroscopy were used to study the high-temperature reaction of 2-bromocaproic, 2-iodocaproic, and 2-bromo-2-phenylacetic acids with acetonitrile. The formation of anomalous transnitrilation products (capronitrile and benzyl cyanide) is a consequence of the initial conversion of 2-halo-substituted caproic and phenylacetic acids to caproic and phenylacetic acids, respectively.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1682–1684, July, 1990.     

Trifluoroacetylation of amines with trifluoroacetic acid in the presence of trichloroacetonitrile and triphenylphosphine

We developed a mild and convenient trifluoroacetylation process for amines using a combination of trichloroacetonitrile and triphenylphosphine. The reaction that we designed is applicable to the trifluoroacetylation of a wide variety of amines, including amines with stereogenic centers, which underwent trifluoroacetylation without racemization.     

Reactions of 1,5-diketones with hydrogen selenide in the presence of trifluoroacetic acid

Two competing pathways were found in the transformations of 1,5-diketones and the 4H-selenopyrans formed from these diketones upon reaction with CF₃CO₂H in the presence of hydrogen selenide entailing disproportionation and the electrophilic addition of hydrogen selenide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1634–1637, December, 1984.     

Fluorination with xenon difluoride. Reactions of phenyl-substituted olefins in the presence of trifluoroacetic acid

Trifluoroacetic acid-catalyzed liquid-phase fluorination with xenon difluoride of phenyl-substituted olefins, e.g. cis- and trans-1-phenylpropene and cis- and trans-stilbene, results in the formation of vicinal difluorides and fluoro-trifluoroacetates. The reaction is non-stereospecific. d,1-Erythro and d,1-threo fluoro-trifluoroacetates are formed in a highly regiospecific Markovnikov manner in 50% yield. The formation of β-fluorocarbonium ions is suggested.     

A kinetic study of the mechanism of esterification of 1-arylethanols in trifluoroacetic acid

Aryl substituent effects upon the rate constants for the esterification of a series of 1-arylethanols in trifluoroacetic acid are in accordance with a reverse A_AL1 mechanism, for which the Hammett reaction constant ? = ?3.69 has been determined by correlation with σ⁺ substituent constants. The rates of reaction are ca. 50-fold faster than those for corresponding benzyl alcohols which bear an electron-donating aryl substituent and which are also believed to undergo esterification in trifluoroacetic acid by the reverse A_AL1 mechanism; the reverse A_AC2 mechanism applies to benzyl alcohols which bear an electron- withdrawing aryl substituent.     

Chemical transformations of methane in trifluoroacetic acid

The reaction of methane conversion in anhydrous trifluoroacetic acid (TFA) is shown to take place at room temperature and atmospheric pressure and to result in the formation of a resinous product. Signals of ions with molecular weights of 684 and 700 are observed in MALDI-TOF spectra of the dry residue of methane conversion products.     

Activation of molecular oxygen in trifluoroacetic acid

The interaction of molecular oxygen with aqueous trifluoroacetic acid (TFA) led to an increase in pH. This effect was explained by a decrease in the concentration of the protonated CF₃CO₂H₂⁺ and H₃O⁺ species after oxygen was fed in the reactor. Quantum-chemical calculations show that a radical pair can be formed in an activation-free exothermal reaction involving the radical residue of the acid, the CF₃CO₂H₂⁺...³O₂...CF₃CO₂⁻ peroxide radical, and the acid molecule in the CF₃C₂^·...HOO^· collision complex. It was assumed that the activation of molecular oxygen in aqueous TFA solutions, providing the activity of the system in oxidations of various organic and inorganic substrates, is related to the formation of peroxide radicals in them.     

Trifluoroacetylation of 9-methylcarbazole. 2. Peculiarities of the reaction due to the presence of trifluoroacetic acid

A satisfactory model of the intermediate in the formation of polyaryltrifluoromethylmethanes in the trifluoroacetylation of 9-methylcarbazole is 1,1,1-trifluoro-2,2-bis(9-methyl-3-carbazolyl)-2-hydroxyethane. The kinetic isotope effect of the reaction was evaluated. It is shown that the rate of the reaction is determined by the formation of a complex. The trifluoromethylation of 9-methyl-carbazole at 110C is accompanied by demethylation of the substrate under the influence of trifluoroacetic acid.See [1] for communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 329–336, March, 1987.     

Activation of molecular oxygen in trifluoroacetic acid

The possibility of the formation of the H₂O₂^+· cation-radical was determined according to the data from nonempirical calculations for liquid trifluoroacetic acid, which forms a hydroperoxide radical after deprotonation. A catalytic cycle was obtained in which CF₃COOH serves as a catalyst in the oxidation of a substrate by dissolved molecular oxygen.     

Reaction of indoles with trifluoroacetic acid

3-Trifluoroacetyl indoles are formed by the action of trifluoroacetic acid on indole-2-carboxylic acid and its benzo-substituted derivatives. When unsubstituted indole is refluxed with trifluoroacetic acid, it gives 3-trifluoroacetylindole in 30% yield.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1233–1235, September, 1981.     

Nucleation and growth mechanism for the electropolymerization of aniline in trifluoroacetic acid/lithium perchlorate/propylene carbonate medium

In the present work, the nucleation and growth mechanism for the electropolymerization of aniline in propylene carbonate medium containing 0.06 M trifluoroacetic acid and 0.05 M lithium perchlorate was investigated at different potentials on highly oriented pyrolytic graphite (HOPG) by potentiostatic current-time transients (i-t) and atomic force microscopic (AFM) measurements. The electrochemical data fitted with the theoretical curves for nucleation and growth suggest that the electropolymerization of aniline consists of progressive nucleation followed by 3D growth at an early stage and layer-by-layer growth in subsequent periods. The results obtained from transient analysis were in good agreement with the results of the AFM analysis. In our previous studies with aqueous solutions, we observed only progressive nucleation followed by a 3D growth mechanism for the electropolymerization of aniline in a higher potential range, 1.5–2.0 V vs. Ag/AgCl. Hence, the results obtained from the present work indicate that the nucleation and growth mechanism depends on the medium.     

Reaction of arenes with iodine in the presence of potassium peroxodisulfate in trifluoroacetic acid. Direct and simple synthesis of diaryliodonium triflates

Diaryliodonium triflates have been directly prepared by reaction of arenes with elemental iodine in good yields by using K2S2O8 and TFA, followed by treatment with NaOTf. This procedure avoids the use of high temperature and severe reaction conditions.     

Adamantylation of N-aryl and N-arylalkyl acetamides in trifluoroacetic acid

Russian Chemical Bulletin - Alkylation of N-aryl and N-arylalkyl acetamides with hydroxy adamantane derivatives in trifluoroacetic acid was studied. The differentiating effect of trifluoroacetic...     

AgOAc-mediated rearrangement of gem-dibromospiropentanes in trifluoroacetic acid

AgOAc-mediated intramolecular skeleton rearrangement reaction of gem-dibromospiropentanes produced the corresponding naphthalene and indene derivatives in moderate to good yields under mild conditions.     

Chemical transformations of CO2 in trifluoroacetic acid solutions

It is established that a conversion reaction of carbon dioxide takes place at room temperature and atmospheric pressure in aqueous solutions of trifluoroacetic acid (TFA), which leads to the formation of oxalic acid and heavier polymerized products.     

Inverse temperature-dependent pathway of cellulose decrystallization in trifluoroacetic acid

An unusual inverse temperature-dependent pathway was observed during cellulose decrystallization in trifluoroacetic acid (TFA). Decreasing the TFA treatment temperature accelerated the cellulose decrystallization process. It took only 100 min to completely decrystallize cellulose at 0 degrees C in TFA, a result not achieved in 48 h at 25 degrees C in the same medium. There was neither cellulose esterification nor a change of cellulose macrofibril morphology by TFA treatment at 0 degrees C. Our IR data suggest that TFA molecules are present as cyclic dimers when they penetrate into crystalline cellulose regions, transforming crystalline cellulose to amorphous cellulose. On the other hand, the rate of TFA penetration into the cellulose matrix was greatly retarded at higher temperatures where monomeric TFA prevails. At elevated temperatures, esterification of TFA monomers on the external surface of crystalline cellulose, agglomeration of cellulose macrofibrils, as well as water released from the esterification reaction, inhibit the diffusion rate of TFA into the cellulose crystalline region and decrease the TFA swelling capability.