红霉素肟贝克曼重排反应中的构型异构化

碱性条件下红霉素肟容易由E构型转化为Z构型从而达到平衡。但发现同样是在碱性条件下的贝克曼重排反应后,E构型产物的质量分数相对于原料中E肟的质量分数而言提高了,而Z构型产物的质量分数相应降低了,说明在贝克曼重排反应过程中Z构型异构化为了E构型。该异构化现象的发现为控制阿奇霉素生产条件,从而降低产物中由红霉素Z肟重排得到的副产物的质量分数,提高最终产品阿奇霉素的产率提供了参考,对异构化机理也进行了探讨。

类硅烯[CH(R)N]_2SiLiF(R=H和t-Bu)的构型及异构化反应

用密度泛函理论(DFT)在B3LYP/6-31G(d)计算水平上首次研究了N-杂环类硅烯[CH(R)N]_2SiLiF(R=H和t-Bu)的构型及异构化反应。计算得到了[CH(H)N]_2SiLiF的五个平衡构型和[CH(t-Bu)N]_2SiLiF的四个平衡构型。两种类硅烯的各构型中,包含四元环结构的p-络合物构型都是最稳定的,是实验上可能存在的构型。三元环构型、σ-络合物构型和"经典"四面体构型都是不稳定的。t-Bu基团增强了σ-络合物构型的稳定性,但减小了类硅烯的复合能,从而进一步证明了t-Bu取代的硅烯的稳定性。

Comparison on Commercial Application of Two Types of C_8 Aromatics Isomerization Catalysts

The results of commercial application of two types of C_8 aromatics isomerization catalysts under different feed conditions were compared to gain an insight in the techno-economical basis for selecting proper technological route at the plant.The comparison reveals differences in every aspect of feed consumption,unit capacity,product output,product distribution,and unit process parameters depending upon which catalyst type is adopted by the integrated PX complex.The type of aromatics isomerization catalyst has its influence on the plant scale,the construction cost,the process unit capacity and the product cost,with the magnitude of its impact varying with changing feed conditions.