摘要
一定条件下,偶氮氯膦Ⅲ的重稀土螯合物可由α型转化成β型。连续扫描的谱图表明:α型是瞬时形成的。随着反应进行,α峰下降而β峰上升。在恒溫、Yb:R=1:1和pH=3.2时,测得非缓冲体系和缓冲体系(NaAc—HCl)的反应级数分别为2和1,表观活化能分别为71.1KJ/mol和49.8KJ/mol。对于许多缓冲体系,具有亲核基团的缓冲介质能够加速此转化过程。在此缓冲体系中,β型螯合物的生成速率随氢离子浓度的增大而减小,随缓冲介质浓度增大而增大。实验还表明:两个α型分子形成一个β型分子并释放出一个质子。据此,对缓冲体系和非缓冲体系分别拟出了合理的机理,稳态处理后的动力学速率方程满意地解释了所有实验事实。最后讨论了反应机理的可能模式。
Under a certain experimental condition,a-type of heavier rare earths chelates of chlorophosphonazo(III)can be converted toβ-type.In continuous scanning spectrogram,it is shown thatα-type is formed instantaneously.Theα-peaks decline and theβ-peak raises when the reaction is in process.when Yb:R=l:1 and pH=3.2,we had determinated at constant temperature that the order of reaction is equal to 2 and 1 for nonbuffer system and buffer system(NaAc-HCl)while apparent activation energy is equal to 71.7 KJ/mol and 49.8KJ/mol,respectively.For many buffer systems of interest,it is clear that buffer medium of having nucleophilic groups can accelerate the converted process.In these buffer systems the observed formation rate ofβ-type chelates decreases with increasing of hydrogen ion concentration and increases with the buffer medium concentration.The experimental result tells us that two a-type molecules combine into aβ-type molecule and liberate a proton at the same time.With these information,therefore,we can suggest a reasonable mechanism for nonbuffer system-and the differential rate equation,obviously,is-For buffer system a reasonable mechanism will be.The differential rate equation becomesIn accord with these results,we can satisfactorily explain all experimental facts.At last,the geometrical configuration and the reaction mode are discussed in this paper.
作者
林智信
曾云鹗
Lin Zhixin;Zeng Yune(Department of Chemistry,Wuhan University,wuhan)
出处
《高等学校化学学报》
SCIE
EI
CAS
1982年第2期243-250,共8页
Chemical Journal of Chinese Universities