A probe method for studying dibromocarbene by time resolved infrared spectroscopy

Dibromocarbene reacts with tertiary-butylisocyanide to form a ketenimine. The absolute rate constant of the reaction (kTBI = 2.3 × 109 M−1 s−1) was determined by laser flash photolysis techniques with UV–vis detection of the dibromocarbene–pyridine ylide. The ketenimine was detected by TRIR spectroscopy at 2040 cm−1. Isocyanide trapping of carbenes to form ketenimines is proposed as a general method of studying IR silent carbenes by TRIR spectroscopy.