Ab initio investigation of the O–H insertion reactions of CH₂X–X(X = Cl, Br, I) isopolyhalomethanes with water

Here, we report ab initio calculations for the O–H insertion reactions of CH₂X–X(X = Cl, Br, I) with H₂O and examine substituent effects for changing the halogen atom. As Cl changes to Br and then I, the O–H insertion reactions lead to an HX acid leaving group and range from about 2.3 kcal/mol for X = Cl to about 16.3 kcal/mol for X = I. We compare the trends as the halogen atom varies from Cl to Br and I in the O–H insertion reactions of CH₂X–X with H₂O to the cyclopropanation reactions of CH₂X–X with ethylene. We very briefly discuss possible implications for phase-dependent photochemistry of polyhalomethanes in the atmosphere.