高等学校化学学报 ›› 2002, Vol. 23 ›› Issue (7): 1285.

• 研究论文 • 上一篇    下一篇

电化学监测酸碱滴定法测定(R-H)键的异裂自由能

曾青, 何家骐, 程津培   

  1. 南开大学化学系, 天津 300071
  • 收稿日期:2001-05-28 出版日期:2002-07-24 发布日期:2002-07-24
  • 通讯作者: 程津培(1948年出生),男,博士,教授,博士生导师,中国科学院院士,从事物理有机化学理论研究.E-mail:ChengJP@mail.most.gov.cn E-mail:ChengJP@mail.most.gov.cn
  • 基金资助:

    国家自然科学基金(批准号:29392206)

Heterolytic (R-H)Bond Dissociation Free Energies in Solution Derived from Electrochemically-monitored Acid-Base Titration(EABT)

ZENG Qing, HE Jia-Qi, CHENG Jin-Pei   

  1. Department of Chemistry, Nankai University, Tianjin 300071, China
  • Received:2001-05-28 Online:2002-07-24 Published:2002-07-24

摘要: 建立一种电化学监测酸碱滴定(EABT)方法,利用循环伏安(CV)技术直接观测正离子基(RH)酸解过程中各物种浓度的变化,从而得到酸性离解常数(pKRH)和键异裂自由能(ΔGhet).所测吩噻嗪系列在二甲基亚砜和乙腈中的pKRH与文献中用间接法得到的pKRH值相当吻合,证实了本方法的可信度.由于不需要间接方法所必需的中性母体分子的pKa和负离子氧化电位,故该方法可适用于难于测定的大量有机体系pKRH常数的研究.

关键词: RH+·, 酸性离解常数, 正离子基, 循环伏安, 键异裂能

Abstract: An Electrochemically Monitored Acid Base Titration(EABT) method using cyclic voltammetry was established to measure directly the concentration change of all species, then to get the acidic dissociation constants(pKRH ) and bond heterolysis energies(Δ Ghet ) of radical cations. pKRH s of phenothiazine and its analogues in dimethylsulfoxide and acetonitrile were obtained and in good accordance with the pKRH s derived from indirect methods. So, the credence of the present method was tested. Because the exact values of p Ka(or BDE) of the parent molecules and of the anion oxidation potentials needed by indirect methods are not required, the EABTmethod can be applicable to a wide range oforganic systems whose pKRH s may otherwise be difficult to be obtained.

Key words: pKRH, Radical cation, Cyclic voltammetry, Bond heterolysis energy

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