紫外光照下尿嘧啶在磷酸盐水溶液中的新型光化学反应研究

在中压汞灯光照下,无机磷酸盐能促进尿嘧啶水溶液(pH=8)的光解作用(磷酸盐效应),发生嘧啶碱基的光解取代反应,主要光解产物为6-磷酸基尿嘧啶(C₄H₅N₂O₆P).通过元素分析,UV,IR,EIMS,¹HNMR,¹³CNMR,³¹PNMR等测试手段和方法,确定了光解产物的组成和结构.实验表明,在中压汞灯的发射光谱(连续光谱)中,对磷酸盐效应起作用的波长为190～220nm.

New Photochemical Reaction of Uracil in Phosphate-buffered Saline Under UV Irradiation

Under UV irradiation the photoreaction of pyrimidine bases in aqueous solution has involved three types of reactions, (1) namely nucleophilic addition of water, ethanol, or hydrogen cyanide at the 5,6-double bond; (2) dimerization by addition at the same double bond; (3) ring cleavage. It was reported that the presence of phosphates altered the course of the photolysis process of pyrimidine bases and derivatives under the irradiation of low pressure mercury lamp(LPML, 254 nm), but the role of phosphate in the mechanism was not clear. In previous papers we found a new type of the photoreaction(replacement reaction) of pyrimidine bases in phosphate aqueous solutions under the irradiation of medium pressure mercury lamp(MPML). The photoreaction of 1.0×10-4 mol/L uracil in 0.05 mol/L phosphate solution by irradiation of MPML was reported and the photoreactive enhancement of uracil by adding phosphate was found, which produced a novel compound. The composition and structure of the compound was identified by elemental analysis, EI-MS, UV, IR, 1H NMR, 13C NMR,31P NMR. Filter experiments demonstrate that the wavelengths(190—220 nm) in the spectrum of MPML are responsible for the phosphate-induced enhancement.