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过去,我们在有机化学教学中,讲授结构和性质的关系时,介绍甲基供电性的概念是必要的,但并不全面。随着科学技术的发展以及理论和实验水平的提高,对甲基供电性的概念有所发展。近年来,有些文献报导了甲基的吸电性。这样甲基不但可以作为供电基,也可以作为吸电基。究竟是“供电”还是“吸电”,要看甲基处在什么体系中。一、甲基作为吸电基当甲基连到SP~3杂化碳原子(烷烃体系中的饱和碳原子)上时,甲基为吸电基。这种情况可由偶极矩的数据及动力学的研究等方面得到证实。Lide用微波法测定了异丁烷的偶极矩,其数值为0.132D,但不能确定其方向。为了确定其方向,Lide把异丁烷分子中的次甲基上
In the past, when we talked about the relationship between structure and nature in organic chemistry teaching, it is necessary to introduce the concept of methyl electricity supply, but it is not comprehensive. With the development of science and technology and the improvement of theory and experiment level, the concept of methyl electricity supply has been developed. In recent years, some papers reported the electronegativity of methyl. Such methyl can not only be used as a power base, but also as a base. Whether it is “power supply” or “power-off” depends on what system methyl is in place. I. Methyl as Electro-Absorption Base When methyl is attached to SP 3 hybridized carbon atoms (saturated carbon atoms in the alkane system), the methyl group is an electron-withdrawing group. This situation can be dipole moment data and kinetic studies have been confirmed. Lide measured the dipole moment of isobutane by the microwave method, its value is 0.132D, but can not determine the direction. To determine its orientation, Lide puts the isobutane molecule in the methine group