The reaction of CHBr3/CHCl3 or CHBr3/CCl4 with magnesium under general Grignard reaction condition is studied and is for the first time found to produce dihalocarbene which is trapped with some different olefins to prepare the gem-dihalocyclopropane derivatives in good yields. The reaction having advantages of easy work-up, mild reaction condition and high yield is a novel convenient method for the generation of dihalocarbene. A possible mechanism (Single Electron Transfer, SET) is described. The effect of different reaction condition on the reaction is studied.

Key words: METHANE P, MAGNESIUM, REACTION MECHANISM, INFRARED SPECTROPHOTOMETRY, CARBENE, PROTON MAGNETIC RESONANCE SPECTROMETRY