Carbonate dianion buffer

The absence of catalytic cleavage of nonionized phthalimide in the presence of carbonate buffer solution cannot be attributed to the steric requirement of carbonate dianion, because trimethylamine and DABCO may be considered to have the same or even more steric requirements than carbonate dianion. The most... 

The 5,8-dihydroxy-4(3//)-quinazolinones possess three protons capable of dissociation in aqueous buffer, viz. N3—H and the protons of the 5- and 8-hydroxyl groups (Scheme 107). Initial acid dissociation of the N3 proton does not take place at low pH because electron-rich substituted quinazolin-4(3//)-ones possess pK values greater than 10. The first dissociation is from the 5-hydroxyl which affords an anion (697) which is stabilized by internal hydrogen bonding expressed by pK 7.3 (7.8). Cleavage of the halogen-carbon bond in the 2-substituent in (697) involves a rate-determining reaction of the hydroquinone monoanion and dianion species, since there is an approximate 100-fold difference in rate constants between the precursor 2-chloro (696 X = Cl) and... 

The very useful A-sulfonyloxaziridines are conveniently prepared by treating A-sulfonylimines with Oxone in a biphasic solvent system (eq 18). Either bicarbonate or carbonate can be used to buffer this reaction, but reaction is much faster with carbonate, suggesting that the monopersulfate dianion is the oxidizing species (for illustrations of the remarkable chemistry of these oxaziridines, see N-(Phenylsulfonyl)(3,3-dichlorocamphoryl)-oxaziridine). 

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