The carbenoids 2 undergo at -110-degrees-C a bromine/lithium exchange reaction with 1,1-dibromo alkanes. This leads to partial equilibration of the carbenoids 2 during their generation from the 1,1-dibromo compound 1. In the absence of the precursor 1, the carbenoids 2 have been found to be configurationally stable at -110-degrees-C.