N-Nitrososulfamates: Sources of Carbonium Ions in Aqueous Media and Substrates in Solid-State Decompositions

Potassium N-nitrososulfamates of benzylamine, 2-phenylethylamine, and cyclohexylamine 2a-c were synthesized and examined as sources of carbonium ions in aqueous media. The nitrososulfamates are crystalline compounds which decompose readily at low pHs (~2) under conditions where the parent amines are relatively stable to nitrous acid. In water solutions they produce the corresponding alcohols, principally, along with small percentages of the corresponding esters of potassium bisulfate. The decomposition of the benzyl analogue 2b in the presence of sodium thiocyanate produced, principally, benzyl alcohol, but also benzyl thiocyanate and benzyl isothiocyanate in a ratio of 4.4/1, indicating a muted role for nucleophilicity in this carbonium ion reaction. In sulfate buffers they decompose by psuedo-first-order kinetics (rate constants are reported). In acetic acid they produce principally the corresponding acetate esters. A reaction mechanism is proposed in which the slow step involves the production of a diazohydroxide rather than a direct formation of a carbonium ion. The benzyl analogue 2b is an inhibitor of the enzyme pepsin; it also undergoes a photoelimination reaction on irradiation. The nitrososulfamates are perfectly stable when dry, but they undergo a relatively rapid solid-state decomposition (T_1/2 ≈ 2-5 days) when exposed to normal atmospheric humidity; surprisingly, the external appearance of the crystals does not change during the decompositions. The products are, principally, the esters of sulfuric acid and potassium bisulfate.