Bond selective photochemistry in CH2BrI through electronic excitation at 210 nm

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Abstract
To explore the possibility of bond selective photochemistry in an excited electronic state, we have studied the photolysis of CH2BrI in a molecular beam at 210 nm. Following the direct local excitation of a repulsive transition on the C–Br bond at 210 nm, the fragments were detected by time‐of‐flight mass spectrometry. The dominant channel was found to be C–Br fission (60%) releasing an average of 15 kcal/mol into translation with the remainder reacting to form CH2+IBr and CH2+I+Br. There was no evidence for the primary fission of the C–I bond, making this the first clear example of the selective cleavage of a stronger bond in a molecule over the weakest one.