四苯硼钠、四丁基溴化铵和溴化钠在二肽-水混合溶剂中的电导性质

Conductance Studies of NaBPh4,NBu4Br and NaBr in Dipeptide-water Mixed Solvents

采用电导法测定了298.15 K时四苯硼钠(NaBPh4)、四丁基溴化铵(NBu4Br)和溴化钠(NaBr)在二肽-水混合溶剂中的电导率,进而计算得到了3种电解质在这些体系中的极限摩尔电导率及其组成离子的极限摩尔电导率、归一化Walden值R和Stokes半径.结果表明,3种电解质在二肽-水混合溶剂中的极限摩尔电导率随二肽-水溶液中肽浓度的增加而减小,这是由混合溶剂微观黏度的增加和电解质被肽优先溶剂化引起的.在结构性强的肽水溶液中,结构破坏性离子Na+和Br-比结构促进性离子BPh4-和NBu4+有较大的R值,且Na+和Br-的Stokes半径随肽浓度的增加而增大的幅度较小,说明在二肽-水混合溶剂中,BPh4-和NBu4+被溶剂化的程度更大,离子在溶剂中的行为主要受溶剂结构因素的影响.

The conductivity data of the electrolyte（NaBPh4,NBu4Br and NaBr）＋dipeptide＋water ternary systems are measured at 298.15 K.Based on the molar conductivity,the limited molar conductivity of the electrolytes,limited ionic molar conductivity,ionic Walden value normalized to their values in water R and Stokes radius of ions are evaluated.The results show that the limited molar conductivity data of three studied electrolytes in the dipeptide-water mixed solvents decrease with the increasing concentration of the dipeptide. This can be ascribed to the increase in viscosity of solvent and the presotvation of electrolytes by peptide molecules. In the aqueous solution of peptide, the structure-breaking ions of Na^＋ and Br^- have the larger R values than the strucvure-making ions BPh4 and NBu4^＋ . The Stokes＇ radius of Na^＋ and Br ions doesn＇t increase a lot with the increasing of the peptide concentration compared to BPh4^- and NBu4^＋ ions. These indicate that BPh4^- and NBu4^＋ ions are largely solvated. The behaviour of these ions is mainly affected by the solvent structure.