The calculated energy of the reaction between Ph3CH and the pyrosulfate that forms [Ph3C][SZO300] is -34.7 kcal mol -1 . The Ph3C + fragment is planar at the central carbon (SCCC = 359.9), as expected for the sp 2 hybridized carbocation. Much like the calculated TEPO*SO3 and pyridine*SO3 adducts discussed above, the sulfur has a tetrahedral structure with SOSO of 330.8 and S-H bond length of 1.361 Å and S-O bond lengths of 1.454, 1.456, and 1.498, respectively. The calculated S-H stretch is 2501 cm -1 , which is close to a weak band at 2590 cm -1 in [Ph3C][SZO300] observed experimentally (Figure ). 9,10-dihydroanthracene (DHA) reacts with SbCl5 to form isolable [DHA][SbCl6]. 25 DHA-d4 could serve as a probe for reversible hydride abstraction by transient SO3 if H/D exchange is observed. Contacting SZO300 with DHA-d4 (5.4 mmol g -1 ) at 25 o C in cyclohexane-d12 results in a bright orange solid. HD, the expected product that forms from reaction of a Brønsted site with DHA-d4, was not observed in this reaction (Figure ). After 60 min at 25 o C the solution phase 1 H NMR spectrum contains signals for DHA-d0 and DHA-d4-x, 26 indicating that ~79 % of DHA-d4 undergoes reversible H/D exchange under these conditions. The FTIR of SZO300 after H/D scrambling contains nO-D bands. These bands are not present in SZO300 after soaking in cyclohexane-d12 solutions containing DHA, indicating that DHA-d4 is the source of deuterium. A plausible mechanism for this behavior is shown in Scheme 1. Pyrosulfate sites reversibly abstract deuteride from DHA-d4 to form the DHA + . Scrambling of -OD sites with nearby -OH sites and subsequent recombination generates DHA-d3. Repetition of this sequence results in the observed DHA-d0 and DHA-d4-x mixture.