Infrared Spectrum\nof the Adduct 2‑Chloro-2-hydroperoxybut-3-ene\n[(C<sub>2</sub>H<sub>3</sub>)CCl(CH<sub>3</sub>)OOH] of the Reaction\nbetween the Criegee Intermediate Methyl Vinyl Ketone Oxide [C<sub>2</

Methyl vinyl ketone oxide (MVKO, C<sub>2</sub>H<sub>3</sub>C(CH<sub>3</sub>)OO) is an important Criegee intermediate produced\nfrom ozonolysis\nof isoprene, which is the most abundant nonmethane hydrocarbon emitted\ninto the atmosphere. Reactions between Criegee intermediate and hydrogen\nchloride (HCl) are important because of their large rate coefficients.\nIn this work, we photolyzed a mixture of (<i>Z</i>)-(CH<sub>2</sub>I)HCC(CH<sub>3</sub>)I/HCl/O<sub>2</sub> at 248 nm\nto produce MVKO to carry out the reaction MVKO + HCl and recorded\ninfrared spectra of transient species with a step-scan Fourier-transform\ninfrared absorption spectrometer. Eleven bands near 1415, 1381, 1350,\n1249, 1178, 1118, 1103, 1065, 978, 931, and 895 cm<sup>–1</sup> were observed and assigned to the hydrogen-transferred adduct (C<sub>2</sub>H<sub>3</sub>)CCl(CH<sub>3</sub>)OOH (2-chloro-2-hydroperoxybut-3-ene,\nCHPB) according to the predicted IR spectrum using the B3LYP/aug-cc-pVTZ\nmethod; the conformation could not be definitively determined. According\nto calculations, most low-energy conformers can interconvert, and\nthe most stable conformers <i>anti</i>–<i>trans</i>-CHPB and <i>syn</i>–<i>trans</i>-CHPB\nmight have the major contributions. Four bands near 1423, 1360, 1220,\nand 1080 cm<sup>–1</sup> were observed and tentatively assigned\nto the OH-decomposition products (C<sub>2</sub>H<sub>3</sub>)CCl(CH<sub>3</sub>)O (1-chloro-1-methyl-2-propenyloxy, CMP); both <i>trans</i>-CMP and <i>cis</i>-CMP might contribute. Unlike in the\ncase of CH<sub>2</sub>OO + HCl and CH<sub>3</sub>CHOO + HCl, in which\nsecondary reactions of the OH-decomposition products reacted readily\nwith O<sub>2</sub> to produce the dehydrated products HC(O)Cl and\nCH<sub>3</sub>C(O)Cl, respectively, the secondary reaction of CMP\nwith O<sub>2</sub> was not observed because there is no feasible H\natom in CMP for O<sub>2</sub> to abstract.