Abstract
Electron-impact-induced fragmentations were performed in the gas phase on δ-silyl aldehydes, ketones, thioketones, carboxylic acids, and acetates. All of these compounds showed significant silyl migration through a transition state with a seven-membered ring. For ketones and acetates, this silyl migration process may overwhelm the McLafferty rearrangement, which involves a transition state with a six-membered ring.