Self-association of nicotinamide in aqueous solution: Light-scattering and vapor pressure osmometry studies
Self-association of nicotinamide in aqueous solution: Light-scattering and vapor pressure osmometry studies
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DOI：
10.1021/js9505197
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发表时间：
1996-08-01
影响因子：
3.8
通讯作者：
Kildsig, DO
中科院分区：
文献类型：
--
作者：
Coffman, RE;Kildsig, DO
烟酰胺是一种水溶助长剂，据报道其在水溶液中自缔合。本研究的目的是表征烟酰胺的自缔合的程度，以及使用光散射和蒸汽压渗透压测定的缔合常数。这两种方法都可以计算缔合常数;然而，虽然光散射测量取决于溶液中颗粒的大小，但蒸汽压渗透压测定法取决于溶液中颗粒的数量。使用光散射，发现烟酰胺主要以二聚体和三聚体的形式缔合。高阶聚集体的特征在于平均聚集数为4.37。二聚和三聚的缔合常数分别为9.99 L/mol和13.1 L/mol。从蒸气压渗透压测定数据计算出二聚常数为0.203 L/mol，三聚常数为14.1 L/mol。相比之下，三聚常数是在良好的协议，而二聚常数相差一个数量级。由于光散射测量对于低浓度的烟酰胺等小分子不太可靠，因此认为由蒸气压渗透压测定法计算的二聚常数更准确。
Nicotinamide is a hydrotropic agent that has been reported to self-associate in aqueous solution. The objective of this study is to characterize the self-association of nicotinamide with regard to the extent of self-association as well as association constants using light-scattering and vapor pressure osmometry. Both methods allow calculation of association constants; however, while light-scattering measurements depend on the size of particles in solution, vapor pressure osmometry depends on the number of particles in solution. Using light-scattering, nicotinamide was found to associate primarily as dimers and trimers, Higher order aggregates can be characterized by an average aggregation number of 4.37. The association constants were 9.99 L/mol and 13.1 L/mol for dimerization and trimerization, respectively. From vapor pressure osmometry data were calculated a dimerization constant of 0.203 L/mol and a trimerization constant of 14.1 L/mol. In comparison, the trimerization constants are in good agreement, while the dimerization constants differ by an order of magnitude. Since light-scattering measurements are less reliable for small molecules like nicotinamide al low concentrations, it is felt that the dimerization constant calculated from vapor pressure osmometry is the more accurate.