Photochemistry of Iodoform in Methanol: Formation and Fate of the Iso ‐CHI 2 ‐I Photoproduct

Ultrafast population and structural dynamics due to the iso ‐CHI 2 ‐I isomer product formed upon UV excitation of iodoform (CHI 3 ) in solution is monitored by femtosecond transient absorption with deep‐UV through near‐IR probing and picosecond transient resonance Raman spectroscopy. Iso ‐CHI 2 ‐I is found to be a major photochemical product regardless of excitation wavelength (266 and 350 nm) and choice of solvent (methanol, acetonitrile, and cyclohexane), and is produced in 50 % quantum yield upon 266 nm excitation of CHI 3 in CH 3 OH. The isomer remains stable up to at least several nanoseconds in C 6 H 12 and CH 3 CN, but undergoes decay with a 740 ps lifetime in CH 3 OH simultaneously with the formation of an iodide ion. In agreement with the experiments, MP2 calculations suggest that iso ‐CHI 2 ‐I readily reacts with CH 3 OH via O‐H insertion/HI elimination reactions.