oa South African Journal of Chemistry - A coloured spin trap which works as a pH sensor : research article
|Article Title||A coloured spin trap which works as a pH sensor : research article|
|© Publisher:||South African Chemical Institute (SACI)|
|Journal||South African Journal of Chemistry|
|Publication Date||Jan 2008|
|Pages||123 - 126|
|Keyword(s)||Free radical, Nitrone, pH sensor, Spin-trapping and Synthesis|
Nitration of 4-hydroxybenzaldehyde afforded 2,6-dinitro-4-hydroxybenzaldehyde 2, which in the presence of thionyl chloride is converted to 4-chloro-2,6-dinitrobenzaldehyde 3. This compound is very reactive towards nucleophiles, and reacts easily with methoxyamine, affording the intermediate 4-aminomethoxy-2,6-dinitrobenzaldehyde 4. Reaction of 4 with N-t-butylhydroxylamine led to a new spin trap of the nitrone type, namely 4-aminomethoxy-3,5-dinitrophenyl-1-t-butylnitrone 6. The spin-trapping capabilities of the new compound have been tested in a classical system, in which short-lived radicals were generated by irradiation. The new compound 6 contains an acidic proton with a pKa value of 7.8, and removal of this by a base induces a colour change, from yellow to green-blue. In a similar way, a new stable nitronyl-nitroxide radical 8 has been obtained from the intermediate 4.
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