1,2,2,6,6-五甲基哌啶醇光稳定作用的研究

本文研究了1,2,2,6,6-五甲基哌啶醇在异辛烷溶液中的光稳定作用。实验结果表明:五甲基哌啶醇具有和四甲基哌啶醇基本相同,而此四甲基哌啶醇氮氧自由基略优的光稳定效率;五甲基哌啶醇和四甲基哌啶醇一样,在光稳定作用过程中产生氮氧自由基,并且氮氧自由基浓度变化经历了一个最大值,但其积累的速度及达到的浓度极大值均比四甲基哌啶醇的场合为低。实验还发现,五甲基哌啶醇在光稳定过程中产生一个稳定中间产物——N-氧化-1,2,2,6,6-五甲基哌啶醇。据此,提出了五甲基哌啶醇首先转化为N-氧化物,进而转化为氮氧自由基的两步作用机理。

STUDIES ON THE PHOTO-STABILIZING EFFECT OF 1,2,2,6,6-PENTAMETHYL-4-HYDROXY-PIPERIDINE

The photo-stabilizing effect of 1, 2,2, 6, 6-pentamethyl-4-hydroxy-piperidine (PMP) in isooctane solution, containing hexadecene-1 and di-t-butyl peroxide, has been investigated. It is shown from the experimental data that the photostabilizing effectiveness of PMP is approximately the same as 2,2, 6, 6-tetramethyl-4-hydroxy-piperidine-(TMP) and slightly higher than that of 2,2,6,6-tetramethyl-4-hydroxy-piperidine-N-oxyl (NO ), and that PMP, as well as TMP, produces N-oxyl in the photostabilizing process of PMP and the concentration of NO produced changes through a maximum. There is a difference related to the production of NO between PMP and TMP. In the case of PMP the rate of cumulation of NO is slower and the maximum value of NO concentration is lower than that in the case of TMP. It has been also found in experiments that a stable intermediate-1, 2,2, 6,6-pentamethyl-4-hydroxy-piperidine-N-oxide (PMPO) is produced in photostabilizing process of PMP. From the above mentioned facts it is suggested that the stabilizing effect of PMP is accomplished by a two-step mechanism in which PMP is first transformed into its oxide PMPO, and then PMPO is further transformed into NO .