Date: 2009. 6. 3, 1:00 PM Place: Rm. L303, Bldg 500 -Abstract- 1-Halovinyllithium carbenoids can undergo the Fritsch-Buttenberg-Wiechell (FBW) rearrangement to form alkynes. This reaction is quite facile when a hydrogen atom is present on carbon 2. The gas phase reaction mechanism may consist of a single step or several steps, depending on the aggregation state of the carbenoid. We examined the FBW reaction of 1-fluoro, chloro-, and bromovinyllithium in the monomer and two isomeric dimers. The migratory aptitude of the hydrogen atoms is dependent on the halogen and the aggregation state.