Conformational Analysis of Trifluoroacetyl Triflate, CF3C(O)OSO2CF3: Experimental Vibrational and DFT Investigation
<p>Definition of the dihedral angles τ<sub>1</sub> = O=C−O−S and τ<sub>2</sub> = C−O−S−C of trifluoroacetyl triflate.</p> "> Figure 2
<p>(<b>a</b>) Potential energy surface and (<b>b</b>) contour map computed with the B3P86/6-31+g(d) approximation as a function of the dihedral angles τ<sub>1</sub> = O=C−O−S and τ<sub>2</sub> = C−O−S−C of trifluoroacetyl triflate varied from −180 to 180° and from 0 to 360°, respectively, in steps of 10°.</p> "> Figure 3
<p>Molecular models of the conformers of trifluoroacetyl triflate computed with the B3LYP/cc-pvtz approximation: (<b>a</b>) <span class="html-italic">syn–anti</span> (the C=O double bond <span class="html-italic">syn</span> with respect to the O−S single bond and the C−O single bond <span class="html-italic">anti</span> with respect to the S−C bond); (<b>b</b>) <span class="html-italic">syn–gauche</span> (the C=O double bond <span class="html-italic">syn</span> with respect to the O−S single bond and the C−O single bond <span class="html-italic">gauche</span> with respect to the S−C bond).</p> "> Figure 4
<p>Gas-phase FTIR spectrum (blue trace, pressure 1.7 mbar, 0.5 cm<sup>−1</sup> resolution, 64 scans), Ar matrix FTIR spectrum (red trace, 1:1000, 0.5 cm<sup>−1</sup> resolution, 256 scans), and liquid-phase Raman spectrum (green trace, λ<sub>exc.</sub> 514.5 nm) of trifluoroacetyl triflate.</p> "> Figure 5
<p>Simulated IR spectra in selected regions for the conformers of TFAT, scaled by their relative abundances at 25 °C, calculated with the B3LYP/cc-pvtz approximation: <span class="html-italic">syn–anti</span> conformer, blue spectrum scaled by 0.69 factor; <span class="html-italic">syn–gauche</span>, green spectrum scaled by 0.31 factor; weighted sum of the spectra of the two conformers, red spectrum, shifted on the vertical axis for clarity purposes only.</p> "> Figure 6
<p>Comparison of the simulated IR spectra in selected regions for the conformers of TFAT, scaled by their relative abundances at 25 °C, calculated with the B3LYP/cc-pvtz approximation: <span class="html-italic">syn–anti</span> conformer, blue spectrum scaled by 0.69 factor; <span class="html-italic">syn–gauche</span>, green spectrum scaled by 0.31 factor; weighted sum of the spectra of the two conformers, red spectrum, shifted on the vertical axis for clarity purposes only and the Ar matrix FTR spectrum of TFAT (black-trace, 1:1000, 0.5 cm<sup>−1</sup> resolution, 256 scans).</p> "> Figure 7
<p>Selected regions of FTIR spectra of an Ar matrix containing TFAT in 1:1000 proportion: after deposition (black trace) and 12 (red trace) and 50 min (blue trace) of irradiation with broad-band UV–visible light. The spectra are normalized to the intensities of the absorption assigned to the <span class="html-italic">syn–anti</span> conformer, for clarity purposes only.</p> "> Scheme 1
<p>Synthesis of trifluoroacetyl triflate.</p> "> Scheme 2
<p>Secondary reactions in the synthesis of trifluoroacetyl triflate.</p> ">
Abstract
:1. Introduction
2. Materials and Methods
3. Results and Discussion
3.1. Synthesis of Trifluoroacetyl Triflate (TFAT)
3.2. Quantum Chemical Calculations
3.3. Vibrational Studies
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Theoretical Approximation | ΔE (Kcal·mol−1) 1 | ΔG° (Kcal·mol−1) 2 | % syn–anti 3 |
---|---|---|---|
B3LYP/6-31++G(d) | 1.26 | 2.22 | 96 |
B3LYP/6-311++G(d) | 1.23 | 2.02 | 94 |
B3LYP/tzvp | 1.11 | 1.34 | 83 |
B3LYP/cc-pvtz | 0.87 | 0.88 | 69 |
MP2/6-31++G(d) | 0.70 | 0.98 | 72 |
Orbital Interaction 1 | syn–anti | syn–gauche |
---|---|---|
lpπO6 → π*C2=O8 | 39.20 | 35.65 |
lpσO6 → σ*C2=O8 | 7.20 | 7.48 |
lpσO6 → σ*S=O4 | 5.42 | − |
lpσO6 → σ*S=O5 | 5.42 | − |
lpσO6 → σ*S−C3 | − | 5.93 |
Total anomeric effect | 18.04 | 13.41 |
Total hyperconjugative effect | 39.20 | 35.65 |
Total | 57.24 | 49.06 |
syn–anti | syn–gauche | |
---|---|---|
Wavelength (nm) | 226 | 229 |
Oscillator strength | 0.0013 | 0.0014 |
Assignment | HOMO → LUMO | HOMO → LUMO |
lppO → π*C=O | lppO → π*C=O |
Experimental a | B3LYP/cc-pvtz c,d | Tentative Assignment | |||
---|---|---|---|---|---|
Gas-FTIR ν (cm−1) | Ar matrix FTIR ν (cm−1) b | Liquid Raman ν (cm−1) | syn–anti | syn–gauche | |
1852 m | 1860 w | 1880 | 1892 (37) | ν C=O syn–gauche | |
1845 w | 1851 | 1882 (38) | ν C=O syn–anti | ||
1465 m | 1475 m | 1455 | 1434 (33) | νas SO2 syn–anti | |
1453 m | 1426 (35) | νas SO2 syn–gauche | |||
1314 w | 1319 vw | 1317 | 1301 (7) | ν C−CF3 syn–anti | |
1315 vw | 1293 (9) | ν C−CF3 syn–gauche | |||
1252 s | 1249 s | 1242 (35) | νas CF3 (−SO2) syn–anti | ||
1248 s | 1241 (64) | νas CF3 (−SO2)syn–gauche | |||
1241 s | 1243 s | 1266 | 1236 (41) | νas CF3 (−C=O) syn–anti | |
1241 s | 1234 (36) | νas CF3 (−C=O) syn–gauche | |||
1234 sh | 1236 m | 1231 (31) | 1231 (29) | νas CF3 (−SO2) | |
1228 m | 1254 | 1225 (27) | 1225 (6) | νs SO2 syn–anti | |
1204 m | 1200 w | 1182 (44) | νas CF3 (−C=O)syn–gauche | ||
1196 m | 1179 (35) | νas CF3 (−C=O)syn–anti | |||
1142 m | 1136 s | 1133 | 1106 (36) | 1106 (42) | νs CF3 (−SO2) |
1040 s | 1047 m | 1061 (100) | ν C−Osyn–anti | ||
1018 m | 1043 (100) | ν C−Osyn–gauche | |||
842 w | 847 w | 840 | 852 (15) | δ OCO syn–anti | |
836 w | 843 (6) | δ OCO syn–gauche | |||
788 w | 788 w | 780 | 774 (7) | δo.o.p. (C=O) syn–gauche | |
786 m | 765 (2) | δo.o.p. (C=O) syn–anti | |||
779 sh | 780 vw | 770 (<1) | 770 (1) | νs CF3 (−SO2) | |
751 w | 746 m | 759 | 741 (9) | δs CF3 (−C=O) syn–anti | |
733 m | 730 w | 734 (8) | δs CF3 (−C=O) syn–gauche | ||
704 sh | 705 vw | 733 | 686 (46) | 686 (46) | ν S−O |
611 m | 611 m | 594 (20) | ω SO2 syn–gauche | ||
609 m | 587 (10) | ω SO2 syn–anti | |||
600 w | 601 w | 585 | 575 (7) | ν C−S syn–gauche | |
598 w | 566 (8) | ν C−S syn–anti | |||
585 sh | 580 vw | 556 (<1) | 554 (<1) | δ CF3 (−SO2) | |
566 vw | 566 w | 559 | 544 (1) | 547 (<1) | δ CF3 (−SO2) |
522 vw | 521 vw | 519 (1) | 517 (<1) | δ CF3 (−C=O) | |
498 w | 496 m | 489 (7) | δ SO2 syn–anti | ||
492 w | 487 (10) | δ SO2 syn–gauche | |||
438 | 432 | 428 | δ O=S=O | ||
421 | 415 | 381 | δ C−C=O | ||
330 | 325 | 335 | δ F−C−C | ||
302 | 300 | 284 | δ F−C−C | ||
276 | 257 | 277 | δ F−C−S | ||
242 | 236 | 243 | ω CF3 (−C=O) | ||
202 | 186 | 200 | δ C−O−S | ||
170 | 159 | 149 | δ O−S−C |
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Spaltro, A.; Peluas, M.G.; Della Védova, C.O.; Romano, R.M. Conformational Analysis of Trifluoroacetyl Triflate, CF3C(O)OSO2CF3: Experimental Vibrational and DFT Investigation. Spectrosc. J. 2024, 2, 68-81. https://doi.org/10.3390/spectroscj2020005
Spaltro A, Peluas MG, Della Védova CO, Romano RM. Conformational Analysis of Trifluoroacetyl Triflate, CF3C(O)OSO2CF3: Experimental Vibrational and DFT Investigation. Spectroscopy Journal. 2024; 2(2):68-81. https://doi.org/10.3390/spectroscj2020005
Chicago/Turabian StyleSpaltro, Agustín, Melina G. Peluas, Carlos O. Della Védova, and Rosana M. Romano. 2024. "Conformational Analysis of Trifluoroacetyl Triflate, CF3C(O)OSO2CF3: Experimental Vibrational and DFT Investigation" Spectroscopy Journal 2, no. 2: 68-81. https://doi.org/10.3390/spectroscj2020005