Trifluoroacetic acid properties

Fluorinated Acids. This class of compounds is characterized by the strength of the fluorocarbon acids, eg, CF COOH, approaching that of mineral acids. This property results from the strong inductive effect of fluorine and is markedly less when the fluorocarbon group is moved away from the carbonyl group. Generally, their reactions are similar to organic acids and they find apphcations, particularly trifluoroacetic acid [76-05-1] and its anhydride [407-25-0] as promotors in the preparation of esters and ketones and in nitration reactions. 

Physical Properties. Trifluoroacetic acid [76-05-1], CF COOH, is a colorless Hquid with a sharp odor resembling that of acetic acid. Its... 

At Smith Kline French a general approach to cephalosporin and penicillin nuclear analogs was developed that utilizes a monocyclic /3-lactam (59) with the correct cis stereochemistry as a key intermediate. This is prepared by reaction of the mixed anhydride of azidoacetic acid and trifluoroacetic acid with imine (58) followed by oxidative removal of the dimethoxybenzyl group. This product could be further elaborated to intermediate (60) which, on reaction with a -bromoketones, provides isocephalosporins (61). These nuclear analogs displayed antibacterial properties similar to cephalosporins (b-79MI51000). 

The proton magnetic resonance spectrum of the product in trifluoroacetic acid shows that the isomeric purity is greater than 90%. The proton magnetic resonance spectral properties for the isomeric amino ketones in both trifluoroacetic acid and chloroform-d are as follows (solvent) 8 (multiplicity, number of protons, assignment, coupling constant J in Hz.) 1-... 

Some commonly used buffers, such as sodium and potassium phosphate, are incompatible with ELSD, but there are ready alternatives. For example, ammonium acetate has similar buffering properties to potassium phosphate, and ammonium carbonate, ammonium formate, pyridinium acetate, and pyridinium formate are options for different pH ranges. Typical mobile phase modifiers that do not meet the volatility criteria can be replaced by a wide variety of more volatile alternates. For example, phosphoric acid, commonly used as an acid modifier fo control pH and ionization, can be replaced by trifluoroacetic acid other acids that are sufficiently volatile for use with FLSD include, acetic, carbonic, and formic acids. Triethylamine, commonly used as a base modifier, is compatible with FLSD other base modifiers that can be used are ethylamine, methylamine, and ammonium hydroxide [78]. 

The reaction of 9,10-borazaronaphthalene (64) with malondialdehyde bisdiethylacetal in trifluoroacetic acid yields a violet product. Its spectroscopic properties are in agreement with structure 65, which is closely related to that of the cycl[3,3,3]azines, but attempts to isolate a solid salt were unsuccessful.90... 

There is an interesting difference in properties between fluoro compounds and the corresponding hydrogen compounds that can be explained by the assumption of the formation of C—H---X bonds. For example, trifluoroacetyl chloride, F CC0C1, has a boiling point below 0°C, whereas that of acetyl chloride is 51°C similarly, trifluoroacetic acid anhydride, (FjCCO O, boils at 20°C and acetic acid anhydride at 137°C. 

The heteroatoms of the heavier heterobenzenes show neither basic nor nucleophilic properties. For example, arsabenzene is not detectably protonated in trifluoroacetic acid 91 nor can it be alkylated with methyl iodide or stronger alkylating agents 92). This contrasts with simple tertiary arsines which show modest basicity 93) and which are good nucleophiles ... 

In acetonitrile/dichloromethane solution this type of dendrimer shows three kinds of emission bands having their origin in the excited state localised within the naphthyl group, a naphthyl excimer, and a naphthyl/amine exciplex. Titration with trifluoroacetic acid revealed that, in spite of formally possessing four nitrogen atoms, the cyclam core undergoes only two successive protonation steps which significantly affect the luminescence properties. 

Becker et al. prepared a series of 10-substituted and 10,10 -disubstituted l,2-di(9-anthryl)ethanes 349 and their photochemical properties have been studied by determining the quantum yields for intramolecular (4tt + 4 77) photocyclomerization and the quantum yields of fluorescence in both cyclohexane solutions [347] (Scheme 96). The quantum yields for the intramolecular cyclization of monosubstituted 1,2-dianthrylethanes are higher than those for disubstituted analogs (see Table 8). Bulky substituents increase the fluorescence efficiencies and decrease the quantum yields for cycloaddition. The rate of the cycloreversion is enhanced by the addition of trifluoroacetic acid. 

A major advantage is the potential to lock (and protect) written information in the photobistable material. A number of chemical gated systems involving mutual regulation of the photochromic event and, for instance, fluorescence, ion binding, or electrochemical properties have been reported.1501 Scheme 19 illustrates a chiral gated response system based on donor-acceptor substituted alkene 17.[511 The photochemical isomerization process of both the M-ds and the P-trans form was effectively blocked by the addition of trifluoroacetic acid. Protonation of the dimethyl-amine donor unit of M-rfs-17a and P-trons-17b resulted in an ineffective acceptor-acceptor (nitro and ammonium) substituted thioxanthene lower half. Since the stereoselective photoisomerization of 17 relies on the presence of both a donor and acceptor unit, photochemical switching could be restored by deprotonation by the addition of triethylamine. 

Analytical Properties Similar separations as obtained using C3 bonded silica, with a much larger pH stability range than silica-based phases useful for protein and peptide separations using TFA (trifluoroacetic acid) as a mobile phase modifier less mechanical stability than silica-based phases Reference 19... 

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