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The reaction of (tBu)2ArP (1a - 1h), where the para position of the Ar group contains electron donating or electron withdrawing groups, with sulfated zirconium oxide partially dehydroxylated at 300 oC (SZO300) forms [(tBu)2ArPH][SZO300] (2a - 2h). The equilibrium binding constants of 1a - 1h to SZO300 is related to the pKa of [(tBu)2ArPH]; R3P that form less acidic phosphoniums (high pKa values) bind stronger to SZO300 than R3P that form more acidic phosphoniums (low pKa values). These studies show that Brønsted acid sites on the surface of SZO300 are not superacidic.
PMID: 30624924 [PubMed - as supplied by publisher]