Fourier transform infrared emission study of the mechanism and dynamics of HOI formed in the reaction of alkyl iodides with O(3P)

Abstract

Vibrationally excited hypoiodous acid (HOI) is observed as a product in the reaction of alkyl iodides with O(3P). Fourier transform infrared emission techniques are used to detect the excited ν1, OH, stretch of the HOI product, to determine the mechanism of HOI production, and to measure the vibrational product state distributions. The HOI product is formed by O atom reaction with two-carbon and larger straight or branched chain alkyl iodides and cyclic alkyl iodides, e.g., C2H5I, n-C3H7I, i-C3H7I, (CH3)3CI, n-C6H13I, and c-C6H11I, but not with CH3I. Experiments with selectively deuterated ethyl iodides provide direct evidence that HOI is formed in a beta-elimination mechanism involving a five-membered ring transition state. The O atom attacks the iodine and then abstracts a hydrogen from the beta carbon during the lifetime of the complex. Time-resolved experiments allow the extraction of nascent vibrational state distributions for the ν1 stretch of HOI (v=1:v=2:v=3) using different alkyl iodides and assuming the radiative rates are given by Aν→ν−1=vA1→0: C2H5I, 0.53(4):0.39(3):0.08(3); n-C3H7I, 0.61(6):0.34(5):0.05(2); and i-C3H7I, 0.54(6):0.38(4):0.08(3). These distributions are nonstatistical with the v=2 states having only slightly less population than those with v=1. For product molecules with up to three quanta of ν1 excitation, more than 50% of the reaction exothermicity is deposited into the OH stretch.

Potential Energy Surfaces for the Reaction of O Atoms with CH3I: Implications for Thermochemistry and Kinetics

“…This situation may be contrasted to that for C 2 H 5 I + O( 3 P), where it has been shown experimentally that HOI is a major product, 19,25,26 a result which is in accord with the G2 PES we have computed for that reaction. 26,27 Kinetic Analysis of IO and OH Production. Quantum RRK theory 28 was employed to investigate part of the singlet PES, in a more detailed consideration of the fate of initally excited CH 3 IO* formed by addition of O to CH 3 I.…”

The direct production of CO(v=1–9) in the reaction of O(3P) with the ethyl radical

“…Reaction of O( 3 P) with C 2 H 5 I leads to the production of C 2 H 5 ϩIO and C 2 H 4 ϩHOI. 28 Both of these hydrocarbon products are then able to react with another O( 3 P) atom in the ways already described, with the former contributing to the reactions 3͑a͒-3͑f͒ that are probed, and the latter being much slower than the sum of channels 3͑a͒-3͑f͒. Diethyl ketone is also able to react with O( 3 P) but at only a very slow rate (kϳ1.7ϫ10 Ϫ14 cm 3 molecule Ϫ1 s Ϫ1 ) and leading only to the OH product.…”

Co-60 gamma radiation assisted diffusion of iodine in polypropylene

“…However, it is quite possible that this broad peak is due to HOI (Hypoiodous acid) species. OH stretch in HOI is reported to show absorbance in the region 3292-3625 cm À1 [31,33]. The chemistry of iodine is quite complex and the simultaneous gamma radiolysis of iodine (I 2 ), oxygen (O 2 ) and PP (C 3 H 6 ) n may lead to the formation of HOI species through several possible reaction pathways.…”

“…This indicates that iodine has interacted with the PP only by forming the Charge Transfer Complexes. Another possibility is that the diffused iodine may have reacted with the PP network to form alkyl iodides, but these are reported to be short lived and undergo photodecomposition [31]. Further, the C-I bonds are weak and can break due to illumination [19].…”