Pertrifluoroacetic acid Reagent

The lithotype profile was investigated in greater detail with the product composition of the different brown coals being reported in Tables 1 and 2. A distinct decrease in the total concentration of detectable oxidation products occurs with darker lithotypes (Table 1). This result is consistent with increasing aromaticity (Figure 2) and the preferential attack on aromatic structures by the pertrifluoroacetic acid reagent. The total destruction of the tertiary structure within the brown coal lithotypes is evidenced by their low yield of insoluble products (Residue) which is primarily composed of mineral matter. 

The great utility of hydrogen peroxide as a reagent for the conversion of sulphoxides to sulphones spurred the investigation of other peroxy-containing compounds. Probably the most commonly used species is peracetic acid which is formed by the reaction of acetic acid with hydrogen peroxide. In addition, other peroxy acids such as pertrifluoroacetic acid and m-chloroperbenzoic acid and hydroperoxides and hydrotrioxides are often used to convert sulphoxides to sulphones. 

Perphthalic acid <550SC(3)619) is an even milder reagent that works even at —20 to 20 °C. Performic, permaleic and pertrifluoroacetic acids are strong oxidizing agents and they are recommended for AT-oxidation of the least reactive substrates. The last of the three is the most commonly used, especially for the oxidation of highly deactivated substrates (Scheme 16) such as perchloropyridine (electronic deactivation) (74MI20501) and 2,6-dibromopyridine (electronic and steric deactivation) (equation 35). 

Pertrifluoroacetic acid may be prepared by the reaction of hydrogen peroxide with trifluoroacetic acid. The following procedure gives an anhydrous solution of the reagent. Add trifluoroacetic anhydride (25 ml, 0.18 mol) dropwise to a stirred suspension of 86 per cent hydrogen peroxide (4.1 ml, 0.15 mol) in ice-cold dichloromethane (70 ml). On completion of the addition stir at 0°C for a further 10 minutes, dry with anhydrous sodium sulphate and use the solution... 

The oxidation of oximes offers an attractively simple route to nitroalkanes from carbonyl compounds. The most effective reagent is pertrifluoroacetic acid in acetonitrile in the presence of sodium hydrogen carbonate as a buffer. Yields are improved by the addition of small quantities of urea to remove oxides of nitrogen. The reaction is illustrated by the conversion of dipropyl ketoxime into 4-nitroheptane (Expt 5.190). 

One of the most important methods for lactone preparation, and hence of the corresponding hydroxy acids (or halogeno acids, Section 5.14.1 above) is the Baeyer- Villiger rearrangment of cyclic ketones by the action of peracids. A wide variety of peracids have been used in this reaction but currently the reagents of choice are pertrifluoroacetic acid, m-chloroperbenzoic acid, and permaleic acid. The mechanism is formulated below for the conversion of an acyclic ketone into an ester. 

Pertrifluoroacetic acid, produced in situ from HP and trifluoroacetic anhydride, is an efficient reagent for B V oxidation of butanone to yield ethyl acetate. The possible mechanism of the oxidation of aliphatic ketones by pertrifluoroacetic acid is discussed. Several organic reactions, including BV oxidations, have been studied by using reactivity and selectivity indexes proposed in the DFT. The concepts of electrophilicity and nucleophilicity have been applied as reactivity descriptors. The local hardness has been applied as well as a selectivity descriptor. The reactivity and selectivity patterns have been studied for the reactants involved in these organic reactions. They have been ranked in theoretical scales, which are comparable with experimental results obtained from... 

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