Infrared chemiluminescence studies of the hydrogen + chlorine fluoride reaction. Energy disposal and branching ratios

Abstract

Publication costs assisted by the National Science FoundationInfrared chemiluminescence under arrested relaxation conditions has been used to study the HF and HCl formation channels of the H + C1F reaction at 300 K. From the relative infrared emission intensities the ratio of channels was determined as 4.4 in favor of HC1, the less exoergic channel. The energy disposal is ( / " ) H a = 0.42, (~R ) H C I = 0.14, (~T ) H c~ = 0.44, and (f\-)HF = 0.57, (~R ) H F = 0.10, (fT)HF = 0.33. The rotational distribution for the HF channel is much broader than for the HC1 channel, which is a consequence of two pathways for HF formation. The low J component is attributed to direct reaction and the high J component to migratory collisions in which the H that intially attacked the C1 end of the molecule migrates and forms HF. Since -57% of the HF distribution can be assigned to a high J component, only about one-half of the HF is formed directly.The migratory aspect of the H + ClF reaction is less important than for the H + IC1 or BrCl reactions recently studied by Polanyi and co-workers. The energy disposal and inferred reaction dynamics for H + ClF are compared to that for H + Clz and H + Fz reactions. Using a numerical procedure, improved HC1 and HF transition probabilities were calculated and these values were used to convert the HC1 and HF rotational line intensities to relative populations. These new HCl and HF Einstein coefficients are presented in the Appendix.

Infrared chemiluminescence: Evidence for adduct formation in the H + CH2XI reaction and studies of the N + CH2X (X = Cl/F/I/H) reactions

“…16 For reactions of H atoms with IX compounds (X ¼ Cl=F), an H migration step following adduct formation has long been recognized. [17][18][19] In the present study infrared chemiluminescence from HCl(v) was observed from the H þ CH 2 ClI reaction, and an adduct seems to facilitate HCl formation. At least two channels are possible: The thermochemistry is not well established, but the enthalpies of reaction (in kJ mol À1 ) based upon our thermochemical estimates, vide infra, are given in parentheses.…”

“…The distribution is nearly flat for v ¼ 1-3 and it is similar to the HX(v) distribution observed from the H þ IX reactions. [17][18][19] For comparison, the HX distributions from H þ ICl, NFCl 2 , CF 3 O and CF 2 Cl are included in Table 1. The H þ CF 2 Cl and CF 3 O reactions give stable molecules before unimolecular HX elimination occurs.…”

The dynamics of the reaction of O(1D) with HBr studied by crossed molecular beams and time-resolved Fourier transform spectroscopy

“…We note parenthetically that the observation of high rotational excitation in the products of the gas phase reaction, to which we have referred earlier, does not contradict the insertion mechanism because Monte Carlo simulations of the o('D) + HCl reaction using a statistical model suggest (60) that the high OH rotational excitation arises from angular momentum constraints and has no unique dynamical origin. It has been noted that the energy partitioning of both the ground state and excited state reactions resembles that of the direct abstraction reaction of F with HBr (34,61). The observation, however, of a marked propensity for production of the II(A') A component in the OH product of the o('D) + HCI reaction (13) implies that the half-filled IT orbital of OH lies preferentially oriented in its rotational plane and remains in the plane of the dissociating triatomic complex.…”

An analytical potential energy surface of the HClF (2A′) system based on ab initio calculations. Variational transition state theory study of the H+ClF→F+HCl, Cl+HF and F+HCl→Cl+HF reactions and their deuterium isotope variants

“…leads to the study of the rate constant branching ratio (k 1 /k 2 ) for each possible interhalogen molecule and its comparison with the study of the reactions with di †erent XY and (or X 2 molecules. Moreover, the hydrogen exchange reaction Y 2 ) between a halogen Y and the HX molecule is a reaction that involves as reactants the products of reactions (1) and (2). These three reactions close the triangle of connections among the three asymptotic regions of the ground potential energy surface (PES) 2A@ of the HXY system.…”

“…In this work, we have studied the three exoergic reactions involved in the HClF system (X \ Cl, Y \ F). In previous studies on reactions (1) and (2) using infrared chemiluminescence techniques, there have been measured detailed rate constants k(v@) and k(v@, J@) at 300 K.1h3 Microscopic branch-ing has also been observed in reaction (2) but not in reaction (1). Infrared chemiluminescence studies of reaction (3) have also furnished detailed rate constants k(v@) and k(v@, J@) at 300 and 1700 K ;4 k(v \ 0, 1, 2), k(v \ 1, J), k(v@ o v) and other detailed rate constants have also been reported in the same work (primed variables refer to the products vibrational and rotational quantum numbers).…”