Forster循环法估算1-萘胺的基态酸式电离常数  

The Estimate of Ground-state Acidic Dissociation Constant by Forster Cycle

作　　者：徐朝翔 陈亮[2] 

机构地区：[1]山西省环境监测中心站,山西太原030027 [2]山西大学化学化工学院,山西太原030006

出　　处：《山西大学学报（自然科学版）》2004年第3期276-278,共3页Journal of Shanxi University(Natural Science Edition)

摘　　要：2-萘酚(2-NOH)的基态与激发态酸碱电离已有诸多报道,比较而言,1-萘胺(NA)的较少,且研究主要集中于低pH介质中1-萘胺离子的酸碱电离过程.最近,文献报道的激发态NA分子中,由于发生分子内电荷转移(ICT)过程而在pH介质中观察到了萘胺的激发态酸碱电离过程,关于萘胺的基态电离常数还未见报道.已经知道,Weller基于Forster循环所得的方程可根据基态热力学以及激发态电子转移能量推测荧光分子在激发态的电离平衡常数.本文根据Forster循环,采用文献中1-NA的激发态酸碱电离常数14,估算得1-NA的基态酸式电离常数pKa为22.It has been reported that both 2-naphthol(2-NOH) and 1-naphthylamine(1-NA) have the intramolecular charge transfer (ICT) characteristic which would greatly decrease their acidic dissociation constant.Recently,the excited state deprotonation of naphthylamines has been estimated to be 14,whereas the research on ground-state acidic dissociation constant of 1-NA has been limited.A possible reason could be the high ground state pKa of the amines,for example,the pKa of NH_3 is 35 and of aniline is 25.An indirect method of determination of excited state equilibrium such as pK~* values,based on the weller equation acquired from Forster Cycle is introduced in this paper.This cycle is simple because it considers only the difference in molar enthalpy change of reaction of ground and excited states,neglecting the difference in molar entropy change Therefore,1-NA as example was selected,its ground-state acidic dissociation constant was estimated to be 22.The feasibility of this method was further validated by (2-NOH).

关 键 词：Forster循环法 1-萘胺 基态酸式电离常数 分子内电荷转移 氨基基态 激发态 2-萘酚 

分 类 号：O623.731[理学—有机化学] O646.5[理学—化学]