Formation reaction mechanism and infrared spectra of anti-trans-methacrolein oxide and its associated precursor and adduct radicals.

ABSTRACT: Methacrolein oxide (MACRO) is an important carbonyl oxide produced in ozonolysis of isoprene, the most abundantly-emitted non-methane hydrocarbon in the atmosphere. We employed a step-scan Fourier-transform infrared spectrometer to investigate the source reaction of MACRO in laboratories. Upon UV irradiation of precursor CH₂IC(CH₃)CHI (1), the CH₂C(CH₃)CHI radical (2) was detected, confirming the fission of the allylic C‒I bond rather than the vinylic C‒I bond. Upon UV irradiation of (1) and O₂ near 21 Torr, anti-trans-MACRO (3a) was observed to have an intense OO-stretching band near 917 cm^-1, much greater than those of syn-CH₃CHOO and (CH₃)₂COO, supporting a stronger O‒O bond in MACRO because of resonance stabilization. At increased pressure (86‒346 Torr), both reaction adducts CH₂C(CH₃)CHIOO (4) and (CHI)C(CH₃)CH₂OO (5) radicals were observed, indicating that O₂ can add to either carbon of the delocalized propenyl radical moiety of (2). The yield of MACRO is significantly smaller than other carbonyl oxides.

SUBMITTER: Cai JR 

PROVIDER: S-EPMC9814089 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature