Radical reactions must be carried out under inert atmosphere as dioxygen is a triplet radical which will intercept radical intermediates. Because the relative rates of a number of processes are important to the reaction, concentrations must be carefully adjusted to optimize reaction conditions. Reactions are generally carried out in solvents whose bonds have high bond dissociation energies (BDEs), including benzene, methanol or benzotrifluoride. Even aqueous conditions are tolerated, since water has a strong O-H bond with a BDE of 494 kJ/mol. This is in contrast to many polar processes, where hydroxylic solvents (or polar X-H bonds in the substrate itself) may not be tolerated due to the nucleophilicity or acidity of the functional group.