Millimeter wave spectrum of bromomethyl radical, CH2Br

Abstract

The rotational spectra of the two isotopic species of the bromomethyl radical, CH2 79Br and CH2 81Br, have been observed in their ground electronic state 2B1 in the 180-470 GHz frequency region, corresponding to a-type transitions from N=8-7 to N=21-20. The radical was produced by hydrogen abstraction of methylbromide (CH3Br) either by chlorine or by fluorine atoms in a free space cell. Hyperfine structure due to the bromine nucleus has been resolved in the observed spectra, and the rotational constants as well as the fine and hyperfine interaction constants were accurately determined for both isotopomers. The inertial defect was determined to be 0.028 96(20) and 0.028 95(20) amu A(2), for CH2 79Br and CH2 81Br, respectively, suggesting a planar structure. By fixing the [angle]HCH bond angle at 124.5 degrees , an effective molecular structure can be derived as r0(CBr)=1.848 A and r0(CH)=1.084 A. A comparison of the molecular structure of various halogen-substituted methyl radicals with respect to the planarity of these radicals is discussed.

On the reaction of ground-state nitrogen atoms with bromomethyl radicals: A computational study

“…1-3 shows that MP2 and B3LYP methods yield in general very similar geometri- Table 1 Relative energies (in kcal mol −1 ) at different levels of theory for the different species involved in the reaction of N( 4 S) with CH 2 Br ( 2 B 1 ) [46,47] which conclude that the reactant CH 2 Br is planar, whereas MP2 predicts CH 2 Br to be non-planar. However, both the small deviation from planarity of the MP2 C s -symmetry minimun (the dihedral angle HCNH is 174.5 • ) and the low imaginary frequency of the transition vector in the planar transition structure (74i cm −1 ), allow us to assume C 2v symmetry for this species whose electronic state is then 2 B 1 .…”

Spin–Orbit Ab Initio Investigation of the Photolysis of Bromoiodomethane

“…In the analysis of the photoproducts of CH 2 BrI, it is necessary to consider the CH 2 [48] ) and 3.49 eV (exptl. 3.67 eV [49] ), respectively.…”

Theoretical kinetic study of the CH3Br+OH atmospheric system

“…The optimized geometries of reactants and both channel products for the various employed basis sets are presented in Table 1, along with available experimental values [35,[39][40][41][42], whereas those of transition states and intermediates are provided in Table 2. Energetic values obtained for both pathways are given in Table 3, together with experimental reaction enthalpies obtained from available enthalpies of formation for each species [43][44][45][46][47][48][49].…”