N-Tritylhydroxylamines: preparations, structures, base strengths, and reactions with nitrous acid and perchloric acid

N-Trityl, N-(4-methoxytrityl), N-(4,4'-dimethoxytrityl), arid N-(4,4',4"-tr imethoxytrityl) derivatives of hydroxylamine; O-methylhydroxylamine, and O- benzylhydroxylamine have been prepared and characterised. Additionally, N,O -ditrityl- and N,O-bis(4,4'-dimethoxytrityl)-hydroxylamines have been made, and the X-ray crystal structure of the former has been determined. The pK( a) value of O-benzylhydroxylammonium in water (6.2) and of its N-trityl ana logue in aqueous acetonitrile (7.5) have been measured. The N-tritylhydroxy lamines all decompose under aqueous acidic conditions to give the correspon ding trityl alcohols, and rate constants for uncatalysed and hydronium ion catalysed reactions of N-(4,4'-dimethoxytrityl)-O-methylhydroxylamine have been measured by stopped flow kinetics at 25 degreesC. This compound compar es in reactivity with N-alkyl-N-(4,4'-dimethoxytrityl)amines rather than wi th 4,4'-dimethoxytritylamine. Attempted nitrosation of N-tritylhydroxylamin e and its O-alkyl derivatives gave trityl alcohol, the intermediate N-nitro so compound being detectable but too unstable to isolate. From N-trityl-O-b enzylhydroxylamine, attempted nitrosation led to the formation of triphenyl methane in addition to trityl-alcohol, benzyl alcohol, and trityl benzyl et her. The mildly acidic conditions used for attempted nitrosation of methoxy -substituted N-tritylhydroxylamines led to deamination before addition of t he nitrosating agent.