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在乙醇溶液中以2-羟基-1-萘醛(2HN)和5-羟基色氨酸(5HTP)为原料直接合成了新的席夫碱目标物2-羟基-1-萘醛缩5-羟基色氨酸(2HN5HTP)。对目标物进行了熔点测定和红外光谱,紫外可见光谱,荧光光谱,核磁共振波谱等方法的表征。研究了荧光光度法测定弱酸碱解离常数的方法,在25℃下测得水溶液中目标物萘酚羟基酸解离常数pKa=9.42;不同极性溶剂(甲醇、乙醇、乙腈、丙酮)与水混合溶液(1+1)中的酸解离常数pKa分别为9.16、9.05、8.76、8.63,表明酸碱的解离与溶液的极性典型相关。进一步通过紫外可见分光光度法测定了各对应解离常数值,结果表明二种方法具有很好的一致性。
A new Schiff base target 2-hydroxy-1-naphthylaraldehyde 5-hydroxy was synthesized directly from 2-hydroxy-1-naphthaldehyde (2HN) and 5-hydroxytryptophan (5HTP) Tryptophan (2HN5HTP). The melting point of the target was measured and characterized by infrared spectroscopy, UV-visible spectrum, fluorescence spectroscopy and nuclear magnetic resonance spectroscopy. A method for the determination of the weak acid-base dissociation constant by fluorescence spectrophotometry was studied. The dissociation constant of naphthol hydroxy acid in aqueous solution was determined at 25 ℃. The dissociation constant of p-hydroxybenzoic acid pKa was 9.42. With different polar solvents (methanol, ethanol, acetonitrile and acetone) The acid dissociation constants pKa in the water mixed solution (1 + 1) were 9.16, 9.05, 8.76 and 8.63, respectively, indicating that the acid-base dissociation is typically related to the polarity of the solution. The corresponding dissociation constants were further determined by UV-Vis spectrophotometry. The results showed that the two methods have good agreement.