氮氧自由基的研究(Ⅰ)--哌啶类氮氧自由基的合成与反应

STUDIES ON NITROXIDES--Ⅰ--THE SYNTHESIS AND REACTIONS OF PIPERIDINE NITROXIDES

本文报导了从4-氧-2,2,6,6-四甲基派啶氧化成4-氧-2,2,6,6-四甲基哌啶-1-氧自由基的一个改进方法,它具有收率高、反应时间短的优点。还对4-氧-2,2,6,6-四甲基哌啶-1-氧与羟胺盐酸盐在不同pH条件下的反应进行了研究:在碱性条件(pH 9—11)下得到该自由基的肟,在近中性条件(pH 7—8)下,得到自由基肟的Beckmann重排产物,在酸性条件(pH 2—5)下,得多一非自由基产物的盐酸盐,其分子式为C_(9)H_(18)N_(2)O_(2)·HCl.4-氧-2,2,6,6-四甲基哌啶-1-氧自由基很容易与抗坏血酸反应,被还原为1-羟基-4-氧-2,2,6,6-四甲基哌啶。对几种氮氧自由基在固态的顺磁共振谱及质谱也进行了测定。

In this paper an improved procedure on the oxidation of 4-oxo-2,2,6,6-tetramethylpiperidine to 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl is described.The improved method gave high yields of the radical product within a much shortened time.The reaction between 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl with hydroxylamine hydrochloride under different pH conditions was studied.It was found that under basic conditions (pH 9-11),the oxime of the radical was obtained,under neutral conditions (pH 7-8),the Beckmann rearrangement product of the oxime was obtained,while under acidic conditions (pH 2-5),a nonradical product was obtained in the form of a hydrochloride which had the molecular formula of C_(9)H_(18)N_(2)O_(2)·HCl.4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl could be readily reduced by ascorbic acid to the corresponding hydroxylamine.The electron spin resonance spectra of the nitroxides in the solid state and their mass spectra were recorded.