Trifluroacetic acid

Trifluoroacetic anhydride is prepared by the dehydration of trifluroacetic acid with P205. It is a colourless liquid (b.p. 39.5°). 

The quality of this library was examined by monosaccharide compositional analysis. A portion of the trisaccharide library was treated with aqueous trifluroacetic acid at 100°C for 4 h. Analysis of the resulting mixture of monosaccharides on a Dionex HPLC system with a PA1 column and pulsed amperometric detection (PAD) showed that galactose, glucose, and mannose were present in approximately the required ratio. 

Abstract Bis(3-methylbutantio) maleonitril has been obtained from the reaction of disodium salt, l-bromo-3 methylbiitan in acetone under nitrogen for 11 hours. MgPz has been synthesized through the cyclotetramerization reaction of magnesium and n-butanol with bis(3-methylbutantio) maleonitril. The metal free pophyrazine derivative was obtained by its treatment with trifluroacetic acid and further reaction of this product with cobalt(II) acetate, nickel(II) acetate and zinc(II) acetate led to the metal porphyrazine (MPz, M = Co, Ni ve Zn). These new compounds have been investigated and characterized by UV, FT-IR, H NMR, GC-MS and elemental analysis methods. 

The NMR spectra (300 MHz) of the model diamides 1 and 2, and the polyamide 3, were recorded in trifluroacetic acid-d (TFA-d). Since the xylaramide component of 1-3 is symmetrical, one observes a single average coupling for H2-H2 and Experimental... 

Acids and bases are used to increase ionisation by protonation or deprotonation of the analyte, and it is important to choose the buffer and buffer strength very carefully because both have a noticeable effect on sensitivity. In the positive mode, high PA additives such as triethylamine (TEA) will successfully compete with the analyte for available protons and show an intense ion at miz 102. Sensitivity can drop substantially when TEA is buffered with trifluroacetic acid (TFA). This is shown in Figure 6.3. The top diagram shows the mass spectrum of a compound analysed using acetonitrile/H20/TFA as the eluent and shows MH at mIz 511. The mass spectram of the same compound when analysed using... 

Stereoselectivity in reductions of acyclic oximes depends on the configuration of C=N bond. ( )-Isomer of oxime 89 produced syn-hydroxylamine 90 in excellent stereoselectivity in reaction with phenyldimethylsilane-trifluroacetic acid while giving anti-product in the reaction with lithium aluminium hydride. Stereoselectivity in reductions of (Z)-isomers of 89 was substantially lower in both cases (equation 62) . It can be assumed that the rules of stereoselectivity established in diastereoselective reduction of ketones can be applied to reduction of oximes as well. 

In contrast, dichloromethane solutions of the nondeprotonated complex are blue emitters (489 nm) but the deprotonated form is non-emissive. The addition of triethylamine to the former makes it non-emissive and, similarly, addition to the latter of trifluroacetic acid forms the emissive complex. 

For H-acid catalysis stereospecifity is lowered and appears to be the same as in the reactions initiated with trifluroacetic acid instead of the ammoniumyl salt. For the cation-radical mechanism the sterically hindered base 2,6-bis(tert-butyl)pyridine does not inhibit the cyclization triarylamine retards this reaction photosensibilized one-electron oxidation of a diene leads to the same products, which are formed in the presence of the ammoniumyl salt. As shown, in the majority of cases only the cation radical chain mechanism of the diene-diene cyclization is feasible (Bauld, Bellville, Harirchian 1987). Meanwhile, cyclodimerizations of 2,4-dimethylpenta-1,3-diene (Gassman Singleton 1984) and 1,4-dimethylcyclohexa-1,3- or -1,4-diene (Davies et al. 1985) proceed through both mechanisms. 

The 9-ferrocenyl-9-barbaralyl cation 32c was found to be stable even in trifluroacetic acid . The C NMR chemical shifts of the cation are similar to that of the protonated barbaralone, reflecting the high stabilizing ability of the ferrocenyl group. 

Trifluoroacetic anhydride is prepared by the dehydration of trifluroacetic acid with P2O5. 

Ethers may be removed commonly by acid, with the THE derivative 1.79 reacting more rapidly than the tert-hutyl ether. Benzyl ethers may be removed under a variety of conditions such as hydrogenolysis, dissolving metal reduction (Na in NH3) and HBr (mild). Methyl ethers are cleaved by refluxing with EtSNa and DME tert-Butyl ethers can be cleaved with trifluroacetic acid (CE3COOH) at 25°C. 

Pal-HI was prepared by the addition of 1.2 equivalents of N-hydroxysuccinimidyl palmitate to a stirred solution of insulin in DMSO containing a 20-fold molar excess of tetramethylguanidine. After 30 minutes, the reaction was quenched with four volumes of O.IN HCl and the reaction mixture chromatographed on a Vydac C4-reversed phase column, eluted with a 0.1% trifluroacetic acid-acetonitrile gradient. Pal-HI (yield -40%) eluted at a solvent composition of about 40% acetonitrile. 

The reaction clearly proceeds via reduction of the iminium salt 208 produced on protonation, and as such the method is limited to indoles sufficiently basic to be protonated by acetic or trifluroacetic acids. 

Addition of phthalide anion to Schiffs base followed by reaction of the addition product with trifluroacetic acid give isoquinolones . ... 

Acidic compounds tail on silica because of interactions between acidic groups (e.g., -CO2H, -OH) and silanols— This may be reduced by the addition of a small amount of acid (e.g., 1% trifluroacetic acid or acetic acid) to the mobile phase, which will maintain acidic groups in a noniomzed form. 

Hexane, u-butyl benzene, toluene, many solvents in the presence of trifluroacetic acid... 

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