Fig. 1: Geometries of species observed in this work.

a Precursor (Z)-(CH2I)HC=C(CH3)I (1). b Iodoalkenyl radical (Z)-C2H3C(CH3)I (2). c Criegee intermediate syn-trans-C2H3C(CH3)OO (3). d Iodoperoxy radical C2H3C(CH3)IOO (4) predicted with the B3LYP/aug-cc-pVTZ-pp method.