RESUMEN
Roytman and Singleton argue that our proposed electrophilic mechanism for the sulfonation of methane in superacid conditions is "not plausible." We clarify certain terms that might have caused misinterpretation of our proposed mechanism and supplement the discussion. We reaffirm that an electrophilic mechanism may be operative under our reaction conditions.
RESUMEN
Direct methane functionalization to value-added products remains a challenge because of the propensity for overoxidation in many reaction environments. Sulfonation has emerged as an attractive approach for achieving the necessary selectivity. Here, we report a practical process for the production of methanesulfonic acid (MSA) from only two reactants: methane and sulfur trioxide. We have achieved >99% selectivity and yield of MSA. The electrophilic initiator based on a sulfonyl peroxide derivative is protonated under superacidic conditions, producing a highly electrophilic oxygen atom capable of activating a C-H bond of methane. Mechanistic studies support the formation of CH3 + as a key intermediate. This method is readily scalable with reactors connected in series for prospective production of up to 20 metric tons per year of MSA.