Comparative Kinetics of the 3-Buten-1-ol and 1-Butene Reactions with OH Radicals: A Density Functional Theory/RRKM Investigation

Abstract

The compared kinetics of the reactions of unsaturated alcohols and alkenes with OH radicals is a topic of great interest from both the theoretical chemistry and the atmospheric chemistry points of view. The enhanced reactivity of an unsaturated alcohol, with respect to its alkene analogue, toward OH radicals has been previously demonstrated, at 298 K, by experimental and theoretical research. In this work, a new comparative investigation of such reactions is performed for 3-buten-1-ol and 1-butene. The model assumes that the overall kinetics is governed by the first OH addition steps of the mechanism. Calculations have been performed at the DFT level, employing the BHandHLYP functional and the cc-pVDZ and aug-cc-pVDZ basis sets, and the rate coefficients have been determined on the basis of the microcanonical variational transition state theory. The rate coefficients obtained for the OH reactions with 3-buten-1-ol (kOH(31BO)) and 1-butene (kOH(1B)) at 298.15 K are lower than the experimental rate coefficient available in the literature, showing deviations of 18% and 25%, respectively. Negative temperature dependence is verified for these rate coefficients. The kOH(31BO)/kOH(1B) ratios have also been investigated as a function of the temperature, suggesting that at room temperature the unsaturated alcohol reacts with the OH radicals faster than 1-butene, by a factor of 1.2, but at higher temperatures (400-500 K), the alkene should react faster, and that the stabilization of prebarrier complexes and saddle points due to hydrogen bonds is no longer an important factor to govern the reactivity of the unsaturated alcohol toward OH radicals, with respect to the alkene analogue.

Kinetics and Mechanism of the NH (X3Σ–) + SO (X3Σ–) Reaction: A Theoretical Approach

“…It should be noted that, as mentioned above, on both surfaces (see Figures S8) the total rate and rate of formation of main products are pressure-independent due to the equilibrium Boltzmann distribution of energy and angular momentum populations. 59 Moreover, there are deep wells on both PESs, in which the deepest wells are −379.9 and −154.2 kJ mol −1 on the 1 PES and 3 PES, respectively. As a result, there is a little probability for deactivation of corresponding intermediates under collision and the possibility of returning of these intermediates to reactants are assumed to be negligible.…”

Atmospheric reactivity of HCCCH2OH (2-propyn-1-ol) toward OH radicals: experimental determination and theoretical comparison with its alkyne analogue

“…In this work we used a valence triple zeta Pople basis set, augmented with diffuse functions in all atoms and including up to f polarization functions in the main atoms and d functions on the hydrogen atoms, 6-311++G(2df,2pd). This is a more extended and complete basis set than those used in similar studies, 23 roughly in between aug-cc-pVTZ and aug-cc-pVQZ in Dunning's nomenclature. 24 The presence of sp diffuse functions helps to describe the more diffuse electron density of the radicals, as compared to that of closed-shell species, especially in the transition states.…”

Temperature dependence of rate coefficients for the gas phase reaction of OH with 3-chloropropene. A theoretical and experimental study

“…In general, the negative dependence of the rate coefficients with the temperature has been justified by a mechanism in which the reversible formation of a pre-barrier complex takes place in the OH radical electrophylic addition to the double bond, followed by an irreversible reaction step through a saddle point, to products. [14][15][16] . In particular, Zhang et al 6 have computationally investigated the gas phase reaction of OH radical with 3-Chloropropene to products at 100 Torr and between 200-600 K temperature range.…”

“…For the OH addition to the double bond reactions, π pre-barrier complexes have been proposed in previous studies [14][15][16]25 , in which the OH radical moiety lies nearly perpendicular to the C=C plane. Such pre complexes were not found in the present work at the level of theory used.…”

“…Calculated rate coefficients are also lower than those predicted by Zhang and coworkers, who adopted a microcanonical method, based on the RRKM model, for the calculation of the rate expression. A comparison among canonical and microcanonical rate coefficients for OH reactions with unsaturated compounds can be found elsewhere 15,16 .…”