Effects of Oxygenation on the Reactions of the Iodiranium Ion c-C2H4I with Unsaturated Compounds in the Gas Phase

Abstract

The potential for ion-molecule reactions to identify alkene functional groups in substrates with increasing oxygenation is explored by using linear ion-trap mass spectrometry. Electrophilic attack by the iodiranium ion, c-C2H4I+ (m/z 155), proceeds at the collision rate with terminal alkenes RCH═CH2 (R = n-Pr), allyl ethers (R = MeOCH2), and nonconjugated methyl esters (R = MeO2CCH2), favoring transfer of the iodenium cation to the point of unsaturation by π-ligand exchange. Density functional theory (DFT) calculations at M06-2X-D3/def2-TZVP revealed a single energy well for π-ligand exchange, allowing for a barrierless and hence kinetically favorable reaction pathway. In contrast, ring-open..