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The products of the thermal decomposition of CH3CHO
3. J. Ernst and K. Spindler, Ber. Bunsenges. Phys. Chem. 79, 1163 (1975).
4. J. Ernst, K. Spindler, and H. G. Wagner, Ber. Bunsenges. Phys. Chem. 80, 645 (1976).
13.Some bond dissociation energies are: D0(CH3–CHO) = 83.0 ± 0.2 kcal mol−1; D0(CH3CO–H) = 87.9 ± 0.4 kcal mol−1; D0(H–CH2CHO) = 95 ± 1 kcal mol−1; D0(H–CO) = 14.4 ± 0.1 kcal mol−1; D0(CH3–H) = 103.4 ± 0.1 kcal mol−1; ΔrxnH0(CH3CHO → CH4 + CO) = –6.0 ± 0.1 kcal mol−1; ΔrxnH0(CH3CHO → HCCH + H2O) = 34.5 ± 0.5 kcal mol−1; ΔrxnH0(CH3CHO → H2 + CH2=C=O)=19.7 ± 0.2 kcal mol−1.
14. S. W. Benson, Foundations of Chemical Kinetics (McGraw Hill, New York, 1960).
15. P. L. Houston, Chemical Kinetics and Reaction Dynamics (Dover, New York, 2006), Example 2.7: The Rice Herzfeld Mechanism for Decomposition of Acetaldehyde, p. 74.
17. B. R. Heazlewood, M. J. T. Jordan, S. H. Kable, T. M. Selby, D. L. Osborn, B. C. Shepler, B. J. Braams, and J. M. Bowman, Proc. Natl. Acad. Sci. USA 105, 12719 (2008).
21. P. Chen, in Unimolecular and Bimolecular Ion-Molecule Reaction Dynamics, edited by C. Y. Ng, T. Baer, and I. Powis (Wiley, Cambridge, England, 1994), p. 371.
22. X. Zhang, A. V. Friderichsen, S. Nandi, G. B. Ellison, D. E. David, J. T. McKinnon, T. G. Lindeman, D. C. Dayton, and M. R. Nimlos, Rev. Sci. Inst. 74, 3077 (2003).
23. A. Vasiliou, M. R. Nimlos, J. W. Daily, and G. B. Ellison, J. Phys. Chem. A 113, 8540 (2009), See Figs. 3 (PIMS measurements) and 4 (matrix IR spectroscopy).
25. P. A. Heimann, M. Koike, C. W. Hsu, D. Blank, X. M. Yang, A. G. Suits, Y. T. Lee, M. Evans, C. Y. Ng, C. Flaim, and H. A. Padmore, Rev. Sci. Inst. 68, 1945 (1997).
27. J. W. Daily, Q. Guan, A. Vasiliou, M. R. Nimlos, and G. B. Ellison, “The thermodynamic and transport properties of a SiC microtubular reactor,” Int. J. Chem. Kin. (to be submitted).
28.In studies at LBNL's Advanced Light Source, the threshold for observation of the m/z 43 peak at 1125 K was found to be as low as 10.1 eV. Consequently, given both experimental estimates of the room temperature threshold, and the bond energy [CH3CO–H]+ bond energy that we have calculated to be about 0.6–0.7 eV (which implies a 0 K threshold for CH3CHO ' CH3CO+ + H of about 10.8 – 10.9 eV), this suggests a substantial amount of vibrational excitation (of order 0.7 eV) in the 1125 K acetaldehyde. This seems to be very large, and is, in fact, inconsistent with preliminary studies of heated acetaldehyde vibrational states via chirped-pulse mm microwave spectroscopy [Kirill Kuyanov-Prozument and R. W. Field, unpublished results, 2011]. An alternative explanation, which cannot be excluded at this point, is that the m/z = 43 signal comes from dissociative ionization of vinyl alcohol (CH2=CH–OH), because IE(CH2CHOH) ≤ 9.33 ± 0.05 eV. There might be a relatively low energy dissociative ionization channel leading to protonated ketene: CH2CHOH+ → CH2=C=OH+ + H.
29. A. Vasiliou, K. Piech, X. Zhang, B. Reed, M. R. Nimlos, M. Ahmed, A. Golan, O. Kostco, D. L. Osborn, J. W. Daily, J. F. Stanton, and G. B. Ellison, “Thermal decomposition of CH3CHO studied by matrix infrared spectroscopy and photoionization mass spectroscopy,” J. Chem. Phys. 2011, (in preparation).
30.Important ionization energies: IE(CH3CHO) = 10.2298 ± 0.0007 eV; IE(CH2=CHOH) ≤ 9.33 ± 0.05 eV; IE(H2O) = 12.61737 ± 0.00025 eV; IE(CO) = 14.0142 ± 0.0003 eV; IE(CH3) = 9.8380 ± 0.0004 eV; IE(CH4) = 12.618 ± 0.004 eV; IE(CH3CH3) = 11.56 ± 0.02 eV; IE(HCCH) = 11.4006 ± 0.0006 eV; IE(CH2O) = 10.8850 ± 0.0002 eV; IE(CH2CH2) = 10.51268 ± 0.00003 eV; IE(CH2CO) = 9.617 ± 0.003 eV.
31.The commercial samples of CD3CHO and CD3CDO are produced by equilibrating acetaldehyde with D2O and base. The proton NMR spectrum of the CD3CHO sample shows that 6% is CD2HCHO arising from incomplete proton/deuteron exchange. This is evident in the 118.2 nm PIMS in Fig. 1. The black trace for CD3CHO shows a small feature at m/z 45 which is assigned to CD2HCO+ produced by dissociative ionization of CD2HCHO. Likewise, the final red trace for CD3CDO diplays a weak band at m/z 47 which is CHD3CDO+. The extent of impurity in the CD3OD sample, 2 %, was determined by integrating the corresponding peaks in the room temperature mass spectrum.
32. A. Vasiliou, K. M. Piech, M. R. Nimlos, J. W. Daily, J. F. Stanton, and G. B. Ellison, “A vibrational analysis of CH3CHO, CH3CDO, CD3CHO, and CD3CDO,” J. Mol. Spectrosc. 2011, (in preparation).
37.The feature at m/z = 20 also arises, in part from Ar++, which is always observed at the ALS facility due to stray high-energy radiation.
38. J. D. Roberts and M. C. Caserio, Basic Principles of Organic Chemistry (Benjamin, California, 1977), pp. 739–740.
39. T. Shimanouchi, Tables of Vibrational Frequencies. Consolidated, Volume I (NSRDS-NBS 39, Baltimore, MD, 1972), methane has four vibrational modes but only the degenerate CH stretch, f2 ν3, and the degenerate deformation, f2 ν4, are IR active. In the gas-phase, ν3 CH4 is observed at 3019.9 cm−1 and ν4 CH4 is found at 1306.2 cm−1. These values shift in an Ar matrix to ν3 = 3032 cm−1 and ν4 = 1305 cm−1. The signal from ν4 is very intense and easy to detect in an cryogenic matrix.
40. B. R. Heazlewood, A. T. Maccarone, D. U. Andrews, D. L. Osborn, L. B. Harding, S. J. Klippenstein, M. J. T. Jordan, and S. H. Kable, “Near-threshold H/D exchange in CD3CHO photodissociation” Nature Chemistry 3, 443 (2011).
52.See P. R. Westmoreland's comments at the end of the 2007 paper by Gupte et al.
56.Acetaldehyde could rearrange to the vinyl alcohol via the methylhydroxycarbene: CH3CHO → [CH3–C–OH] → CH2=CH–OH. But this pathway would predict that the vinyl alcohol resulting from CH3CDO would be CH3CDO [CH3–C–OD] CH2=CH–OD. Figure 2 shows that the vinyl alcohol resulting from CH3CDO is CH2=CD–OH. Likewise, when CD3CHO rearranges, we observe CD2=CHOD and not CD2=CD–OH.
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