Trifluoroacetic propionic

Physical Properties.—In studies of the secondary thioamide. function, the i.r. and, where possible, the Raman spectra of a series of iV-methyl-thioamides XCSNHMe (X = CSNHMe, CSNH2, CONHj, or COjK) and of N- and C-deuteriated products were determined, vibrational analyses were proposed, and the results were compared with data for other JV-methyl-thioamides. The C n.m.r. spectra of a series of tertiary thioamides of formic, acetic, trifluoroacetic, propionic, and... 

When one of the two acids is used in excess and the pk -values of the two acids differ strongly, the salt deficit method should be used with caution. Formic add, acetic acid, propionic acid, and trifluoroacetic acid have been electrolyzed competitively in mixtures of pairs. Formic acid and trifluoroacetic acid are comparable in case of electrolysis, both are more readily electrolyzed than acetic and propionic adds. Deviations are rationalized on the basis of differences in ionization [147]. It might 1 useful in such cases to neutralize both acids completely. Sometimes one of the two acids, although being the minor component, is more favorably oxidized possibly due to preferential adsorption or its higher acidity [148]. In this case the continuous addition of the more acidic add to an excess of the weaker acid may lead to successful cross-coupling [149], The chain length of the two acids should be chosen in such a... 

CijH,7NO, 87848-98-4) see Acrivastine ethyl 3-[4-(o-tolyl)-l-piperazinyl]propionate (CifiH24N202 63853-99-6) see Dapiprazole ethyl A-(p-tolylsulfonyl)carbainate see under ethyl 4-toluenesulfonylcarbamate ethyl trifluoroacetate... 

The factors chosen for study were the concentration of the ion-pairing reagent, the solution pH ( quantitative factors) and the acid chosen for pH adjustment (formic, acetic, propionic and trifluoroacetic acids) ( quahtative factor). The effect of these factors was assessed by using responses that evaluated both the HPLC (the number of theoretical plates and the retention time) and MS performance (the total peak area and peak height) for each of the four analytes studied, i.e. 1-naphthyl phosphate (1), 1-naphthalenesulfonic acid (2), 2-naphthalenesulfonic acid (3) and (l-naphthoxy)acetic acid (4). 

The effect of the buffer on the efficiency of electrospray ionization was mentioned earlier in Section 4.7.1. This is a good example of the dramatic effect that this may have - good chromatographic separation and ionization efficiency with formic, acetic and propionic acids, and good separation, although with complete suppression of ionization, with trifluoroacetic acid (TFA), the additive used for the protein application described previously. Post-column addition of propionic acid to the mobile phase containing TFA has been shown to reduce, or even... 

Acidic modifier Trifluoroacetic acid Formic acid Propionic acid Acetic acid Ionization completely suppressed Good separation/ionization Good separation/ionization Best separation/ionization... 

CR y)-2-Amino-3-(3-hydroxy-l,2,5-thiadiazol-4-yl)propionic acid 42 was resolved into the (—)- and (+)-enantiomers using a semipreparative Crownpak CR(+)-column (150 x 10mm2) equipped with a Crownpak CR(+) guard column (10 x 4.0 mm2) (Daicel). The column was eluted at 0 °C (ice bath) with aqueous trifluoroacetic acid (TFA) (pH 2.0) at 1.5 mlmin-1. After removal of the acidic mobile phase, the pure enantiomers could be crystallized as zwitterions with high ee (99.9%) <2002BMC2259>. The first eluted (—)-enantiomer has the ////-configuration as proved by an X-ray crystallographic analysis. 

Rate constants and Arrhenius parameters for the reaction of Et3Si radicals with various carbonyl compounds are available. Some data are collected in Table 5.2 [49]. The ease of addition of EtsSi radicals was found to decrease in the order 1,4-benzoquinone > cyclic diaryl ketones, benzaldehyde, benzil, perfluoro propionic anhydride > benzophenone alkyl aryl ketone, alkyl aldehyde > oxalate > benzoate, trifluoroacetate, anhydride > cyclic dialkyl ketone > acyclic dialkyl ketone > formate > acetate [49,50]. This order of reactivity was rationalized in terms of bond energy differences, stabilization of the radical formed, polar effects, and steric factors. Thus, a phenyl or acyl group adjacent to the carbonyl will stabilize the radical adduct whereas a perfluoroalkyl or acyloxy group next to the carbonyl moiety will enhance the contribution given by the canonical structure with a charge separation to the transition state (Equation 5.24). 

The selective oxidation of C—H bonds in alkanes under mild conditions continues to attract interest from researchers. A new procedure based upon mild generation of perfluoroalkyl radicals from their corresponding anhydrides with either H2O2, m-CPBA, AIBN, or PbEt4 has been described. Oxidation of ethane under the reported conditions furnishes propionic acid and other fluorinated products.79 While some previously reported methods have involved metal-mediated functionalization of alkanes using trifluoroacetic acid/anhydride as solvent, these latter results indicate that the solvent itself without metal catalysis can react as an oxidant. As a consequence, results of these metal-mediated reactions should be treated with caution. The absolute rate constants for H-abstraction from BU3 SnH by perfluorinated w-alkyl radicals have been measured and the trends were found to be qualitatively similar to that of their addition reactions to alkenes.80 a,a-Difluorinated radicals were found to have enhanced reactivities and this was explained as being due to their pyramidal nature while multifluorinated radicals were more reactive still, owing to their electrophilic nature.80... 

Access to analogues with higher substitution was easily achieved. From either the propionate ester 193 or acetic acid 188, we previously made the propionic acid appendaged 189, which was in turn alkylated to the gem-dimethyl acid 194 in 76% yield (93% based on recycled starting material). The vinylsilane of 194 underwent addition of ozone to eventually afford hydroperoxide 195, and final ring closure was accomplished with trifluoroacetic acid and acetone to afford gem-dimethyl analogue 169 in 19% overall yield from 194 (Eq. 20). 

Methyl formate Methyl acetate Methyl propionate Methyl isobutyrate Methyl difluoroacetate Methyl trifluoroacetate Methyl monochloroacetate Methyl dichloroacetate Ethyl trichloroacetate Methyl trichloroacetate Methyl cyanoacetate Methyl methoxyacetate Methyl benzoate... 

To a solution of the (+)-methyl 2-[2-(N-phenylsulfonyl)indolyl]-2-hydroxy-3-[3-(N-allyl-5-ethyl-l,2,3,6-tetrahydropyridine)]propionate (a mixture of diastereomers at C-2) in dry dimethoxyethane at -50°C under argon was added sodium naphthalenide (1 M in THF). The mixture was quenched with trifluoroacetic acid, and extracted with ethyl acetate (3 times 10 ml). The extract was washed with saturated aqueous NaHC03 solution, dried (MgS04) and evaporated in vacuo to give the (+)-methyl 2-(2-indolyl)-2-hydroxy-3-[3-(N-allyl-5-ethyl-l,2,3,6-tetrahydro-pyridine )]propionate. The mixture of diastereomers was not separated but chromotagraphed over silica gel eluting with hexane/ethyl acetate/10% aqueous NH4OH/MeOH (5 1 1) to remove more polar impurities. 

The early work was done with acetyl chloride catalyzed with lead acetate [2], propionic and butyric anhydrides in xylene without catalyst [49], and several unsaturated carboxylic acids in the presence of trifluoroacetic anhydride (TFAA) [62,63]. 

The specimens were treated according to the method of Nakagami and coworkers [17,18]. Japanese linden Tilia japonica Smik.) was treated with trifluoroacetic acid anhydride and the fatty acids (TFAA method), which included acetic acid, propionic acid, valeric acid, hexanoic acid, decanoic acid, lauric acid, and palmitic acid. Dynamic measurements were made with a torsion pendulum apparatus under a vacuum. An increasing temperature rate was 2°C/min. The amount of introduced side chain per gram of wood is about 4-6 mmol/g [16]. The chemical structure of the treated wood is presented by the formula ... 

Taylor and cowoikers have studied the intramolecular capture of radical cations from the thallium trifluoroacetate oxidation of arylalkanoic acids and arylalkanols. For example, 3-(3,4-dimethoxyphe-nyl)propionic acid (43) on treatment with thallium trifluoroacetale in trifluoroacetic acid containing a small amount of boron trifluoride etherate fw a few seconds gave the oxidized products (44-46 Schenne... 

From computations with basis sets of the polarized 6-3IG type, at SCF and MP2 levels, the change from formic acid dimer to acetic acid dimer has only a very minor influence upon the energetics of binding . This conclusion is indeed verified by resonant laser photoacoustic spectroscopic measurements i 79,181,182 which find further that trifluoroacetic and propionic acid dimers have a very similar binding enthalpy to formic dimer. One may extrapolate that the formic acid dimer Fl-bond energy is probably applicable for most carboxylic acids with alkyl chains replacing the CH group. 

The main reasons for derivatization of steroids are to decrease heat sensitivity of steroids to avoid irreversible adsorption of steroids onto the stationary phase to increase volatihty of steroids to increase the separation efficiency to achieve enhanced selectivity of the separations, and to improve the sensitivity of the detectors. Segura et al. described some important general requirements for derivatization reactions, i.e., a single derivative should be formed for each analyte the reaction should be simple and rapid, and they should occur under mild conditions the derivate should be stable, reproducible, and produced with high yield in quantitative analyses, the calibration curve should be linear. The main derivatization method for steroids is silylation, but other derivatization methods using, for example, acetic acid anhydride, trifluoroacetic anhydride (TFA), pentafluoro-propionic acid (PFPA), or heptafluoroabutyric anhydride (HFBA) could also be used. " For anabolic steroids... 

The t-Boc protein can then be attached to methoxy PEG-succinimidyl propionate in DMSO-TEA mixture. The mPEG-Boc-protein solution can then be extensively dialyzed and lyophilized [14]. Quantitative deprotection of the lyophilized product can then be achieved by reaction with trifluoroacetic acid (TEA) at 0°C. The conjugate can now be purified by using reverse phase-high performance liquid chromatography (RP-HPLC). 

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