High-Temperature Experimental and Theoretical Study of the Unimolecular Dissociation of 1,3,5-Trioxane

Abstract

Unimolecular dissociation of 1,3,5-trioxane was investigated experimentally and theoretically over a wide range of conditions. Experiments were performed behind reflected shock waves over the temperature range of 775 -1082 K and pressures near 900 Torr using a fast response time-of-flight mass spectrometer (TOF-MS) coupled to a shock tube (ST). Reaction products were identified directly and it was found that formaldehyde is the sole product of 1,3,5-trioxane dissociation. Reaction rate coefficients were extracted by the best fit to the experimentally measured concentration time-histories. Additionally, high-level quantum chemical and RRKM calculations were employed to study the fall off behavior of 1,3,5-trioxane dissociation. Molecular geometries and frequencies of all the species were obtained at the B3LYP/cc-pVTZ, MP2/cc-pVTZ and MP2/aug-cc-pVDZ levels of theory, whereas the single-point energies of the stationary points were calculated using coupled-cluster with

Monitoring formaldehyde in a shock tube with a fast dual-comb spectrometer operating in the spectral range of 1740–1790 cm–1

“…It can be seen that the activation energies obtained in different works agree well, with the only exception of the value Fig. 7 reveals that the absolute values of the rate coefficients determined in shock tubes at high temperatures of Irdam and Kiefer [34] (blue) and Alquaity et al [33] (cyan), and the extrapolated flow-reactor value of Hochgreb and Dryer [33] at 700-800 K (magenta), agree well with our values. On the other hand, the extrapolation of the rate coefficients determined at lower temperatures by Aldridge et al [36] (orange), Hogg et al…”

“…This is probably due to the fact that Wang et al [35] fitted their experiments with a single-exponential growth and did not consider the temperature decrease due to the endothermicity of the 1,3,5-trioxane decomposition. The coefficient of Irdam and Kiefer [34] (blue) is only slightly too slow, while simulations with the rate coefficient of Alquaity et al [33] show the best agreement with our measurements. Figure 7 makes these first conclusions even more evident through an Arrhenius representation of the rate coefficients from literature together with the values measured in the current work.…”

“…The red solid line is the best-fit result of the experimental data; while the blue, green and cyan lines are results of simulations using different rate coefficients reported in literature [33][34][35]. An iterative procedure is used to determine the best-fit for each experiment shown in Fig.…”

“…From the measured CO and OH profiles the rates of the reactions H + O 2 = OH + O and CO + OH = CO 2 + H have been improved. Alquaity et al [33] investigated the unimolecular dissociation of 1,3,5-trioxane between 775 and 1082 K and at a pressure of ~ 1.2 bar using high-repetitionrate time-of-flight mass spectrometry (TOF-MS) in a shock tube. At these conditions, formaldehyde was identified as the sole product.…”

A shock tube laser schlieren study of cyclopentane pyrolysis

“…For example, the product of cyclohexane pyrolysis is 1-hexene via ring opening and isomerization, possibly through a biradical intermediate [9,[11][12][13][14][15]. On the other hand, 1,4dioxane produces two different linear ethers (ethylene-glycol-vinyl-ether and 2-ethoxyacetaldehyde) via concerted ring opening and hydrogen transfer [16], whereas 1,3,5-trioxane undergoes a concerted dissociation to form three formaldehyde molecules [17][18][19][20]. In this experimental study, the effect of reducing a cyclic, saturated hydrocarbon ring from 6 to 5 carbon atoms is examined.…”