Trifluoroacetic acid deuterated

Nesmeyanov et a/.545 used a mixture of ferrocene, deuterated trifluoroacetic acid and benzene in the molar ratios 1 2 20 in a preliminary investigation of the reactivity of ferrocene and its derivatives. At 25 °C, rate coefficients were 1,620 x 10-7 (ferrocene) and 19.3 xlO-7 (acetylferrocene). In a subsequent publication by Alikhanov and Shatenshtein543 these values were altered to 1,600 x 10-7 and 1.5 x 10 7, respectively, and a value of 0.77 x 10"7 added for 1,1-diacetylferrocene. Under the same conditions, toluene gave a value of 0.3 x 10-7 so that the activating effects of these compounds relative to benzene can be approximately determined. 

Nesmeyanov et a/.546 have also measured the effects of substituents in deuteration of ferrocene by deuterated trifluoroacetic acid in dichloromethane at 25 °C. Rate coefficients were measured for ferrocene and its derivative in a range of such acid mixtures, the composition of which was omitted, and in some cases the rate of exchange for ferrocene was calculated on the basis of a linear relationship between log and —H0. Results including the calculated knl values are given in Table 161. It should be noted that, in discussing those results, the authors quoted the incorrect partial rate factors for dedeuteration of toluene arising from the use of the incorrect data for benzene (see p. 199). This should be taken into account... 

Firstly, catheter sample 1 was dissolved in deuterated trifluoroacetic acid, and the solution analyzed by [H NMR spectroscopy. The [H NMR spectrum of the sample is shown in Figure 52. The peaks at 1.16 ppm, 2.56 ppm, and 3.40 ppm are consistent with a polyamide-12 (PA-12) structure. The signal at 3.58 ppm can be attributed to tetramethylene glycol (TMG) protons adjacent to the ether linkages. The signal at 1.60 ppm is composed of overlapping resonances from both components. The smaller peaks are most likely due to polymer end groups or protons at the junction of two blocks the material is an amide-ether block... 

The 1H NMR spectra of parbendazole was recorded with a JEOL-PS 100 NMR spectrometer operating at a frequency of 100 MHz and a magnetic field strength of 2.349 T. Spectra were determined over the region 10.8-0.0 parts per million (ppm), with a sweep time of 250 s. Chemical shifts were recorded as S (delta) ppm downfield from tetra-methylsilane (TMS). Proton noise and off-resonance decoupled 13C NMR spectra were measured on a JEOL FX 90Q Fourier Transform NMR spectrometer operating at 90 MHR and spectral width of 5000 Hz (220 ppm). All measurements were obtained with the compound being dissolved in deuterated dimethyl sulfoxide (DMSO-d6) for dT NMR and in deuterated trifluoroacetic acid (TFA-dx) for 13C NMR. 

Evidence that this reduction proceeds mainly via an N-acyl iminium ion intermediate 120 was obtained by carrying out the triethylsilane reduction of 108 in deuterated trifluoroacetic acid (Scheme 49). As before, two C-4 epimeric protected kainoid analogues 121 and 122 were obtained, H NMR showing loss of the C-4 proton in both products accompanied by a simplification in the spin-spin coupling pattern of the C-5 protons.73 A close examination of the 2H NMR spectrum of each diastereoisomer did, however, reveal a trace of deuteration at C-5 indicating that a small percentage of the reduction also occurs via a benzylic carbocation intermediate 123 (Figure 12). 

Deuterated trifluoroacetic acid was prepared by hydrolyzing a slight excess of trifluoroacetic anhydride with D20. The product was purified by distillation and stored under vacuum in sealed glass ampoules until needed. The isotopic purity was estimated from NMR measurements to be at least 95%. 

XMR spectra and peak assignment of PM and PMC are shown in Figure 1. The spectrum of PM was obtained in DMSO, while that of PMC was obtained in DMSO plus 1% deuterated trifluoroacetic acid (TFA). All peaks from TFA were carefully removed for better resolution. A normal APT method was used for the simplification of the peak assignment. 

DEUTERATION Trifluoroacetic acid. Tris(triphenylphosphine)chlororhodium. 

Hanstein and Traylor544 used a 4.3 M solution of trifluoroacetic acid in chloroform to measure the rates of deuteration of (PhCH2)2Hg at 35 °C, for which kx = 2,100 x 10"7. Comparison with other deuteration rates (which, however, were neither quoted nor referred to) was said to give a (CH2HgCH2Ph) = — 1.14 and the ortho para ratio was 0.84. For the compound PhCH2B(OH)j, the rate of deuteration by 3 M tartaric acid at 100 °C was found to be 5 x 10 7 (ortho para ratio = 1.1) and from this a value of ff4 (CH2B(OH)J) of —1.11 was claimed, but without the relevant data used to obtain these c+ values cautious use of them seems appropriate. 

Blackley548 measured the rates of deuteration of biphenylene, fluorene, tri-phenylene, and phenanthrene relative to o-xylene as 6.15 5.85 1.08 1.32, which is in very good agreement with the values of 8.80 7.00 - 1.14 which may be deduced from the detritiation data in Table 159, obtained using anhydrous trifluoroacetic acid. Aqueous trifluoroacetic acid (with the addition in some cases of benzene to assist solubility) was used by Rice550, who found that triptycene was 0.1 times as reactive per aromatic ring as o-xylene (cf. 0.13 derivable from Table 159) whereas the compound (XXXI) was 0.9 times as reactive as o-xylene. An exactly comparable measure is not available from Table 158, but dihydroanthracene (XXXII), which is similar, was 0.51 times as reactive as o-xylene and... 

A relative reactivity of ferrocene benzene of 105-106 has been quoted557 following a kinetic study of the deuteration of ferrocene in acetic acid-trifluoroacetic acid mixtures at 25 °C, but the value is entirely in error, being based on two faulty assumptions. The data are given in Table 166 and a linear plot of log Art versus —H0 was extrapolated to — H0 = 5.0, a rate coefficient of 1.3 x 10 1 being obtained. This was compared to the Gold and Satchell value for dedeuteration... 

Secondly, the five additional catheter samples (2 through 6) were analyzed using H NMR spectroscopy to provide a direct comparison of these samples to the results for catheter sample 1. Approximately 30 mg of each additional sample was dissolved in 1 mL of deuterated 2,2,2-trifluoroacetic acid, and these solutions were analyzed using 1H NMR analysis. The 1H NMR spectra of all five of these... 

Use of deuterated silane and/or acid with this method leads to site-specific deuterium incorporation in the reduced products. Thus, treatment of 2-methyl-l-pentene with one equivalent of deuterated triethylsilane and two equivalents of trifluoroacetic acid at 50° for 24 hours gives 2-rnethylpentane-2-(7l in 90% yield (Eq. 73) 221 In the same way, isopropenylcyclopropane gives an 80% yield of deuterated isopropylcyclopropane after 30 minutes at —10° (Eq. 74).221... 

Trisubstituted Alkenes. With very few exceptions, trisubstituted alkenes that are exposed to Brpnsted acids and organosilicon hydrides rapidly undergo ionic hydrogenations to give reduced products in high yields. This is best illustrated by the broad variety of reaction conditions under which the benchmark compound 1-methylcyclohexene is reduced to methylcyclohexane.134 146,192 202 203 207-210 214 234 When 1-methylcyclohexene is reduced with one equivalent of deuterated triethylsilane and two equivalents of trifluoroacetic acid at 50°, methylcyclohexane-... 

Proton exchange at the meso position of corrole is facile, and the deuteration is complete in 15 min in trifluoroacetic acid at room temperature. Under similar condition, porphyrin does not exchange the meso protons. 

Electrophilic proton exchange occurs readily for sapphyrin (39) and meso deuteration is completed in trifluoroacetic acid and at room temperature overnight.274 The substitution proceeds at a moderate rate for two of the meso protons but very slowly for the other two in the dioxa analogue... 

The spectra of gaseous formic acid found by Millikan and Pitzer (1411) are distinctive because the spectral features indicate spacings independent of the deuteration, in contradiction to the results presented by Josien and Fuson for trifluoroacetic acid, for which the spacing seems to be halved on deuteration (1061). These formic acid spectra are further unusu2il because of the presence of distinctive... 

When trifluoroacetic acid was added to butylcyclopropane derivatives 12, Markovnikov products were obtained predominantly. Treatment of cyclopropane with concentrated sulfuric acid yielded propanol. With the deuterated acid, D2SO4, deuterium was found at all three carbon atoms presumably due to the formation of a protonated cyclopropane intermediate. When exo-tricyclo[3.2.1.0 ]octane (13) was treated with deuterated sulfuric acid an end-on attack of the deuterium ion at the most strained bond with inversion of configuration to give 14 was observed. 

Deuteration and trittation.7 Labeled trifluoroacetic acid has some advantages for deuteration and tritiation. It is obtained in quantitative yield by mixing trifluoroacetic acid and labeled water. It has excellent solvent properties and also functions as the acid catalyst. The uptake of label can be followed by nuclear magnetic resonance the reagent is readily removed by evaporation in vacuo. In the case of olefins, addition to form the trifluoroacetate occurs simultaneously. It lias been used for the labeling of A8- and A9-tetrahydrocannabinol. 

Venkatasubramanian and Krishnamachari required deuterated oxazoles for a study of the flash photolysis of oxazole 1. They obtained (2-D)-oxazole 593 exclusively from 1 using CF3COOD and D2O (Scheme 1.162). The authors did not speculate about this surprising result. The reaction is selective for monodeu-teration, but 1 also suffers decomposition (up to 40%) under the reaction conditions leading to a mixture of 593 and deuterated pyrazines 594 n = 0-4. Trifluoroacetic acid-D was much more efficient than deuterosuUuric acid for this reaction. 

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