Cisisomer: Two identical atoms or groups on the same side of a double bond or ring are cis isomers, also known as cis.
Trans isomer: Two identical atoms or groups on both sides of a double bond or ring are trans isomers, also known as trans.
Production conditions:
At least one bond in the (1) molecule cannot rotate freely (otherwise it will become another molecule);
⑵ Double bonds cannot have the same group on the same carbon.
speciality
Isomerization refers to the same molecular formula but different structural formulas, and cis-trans isomerization refers to different spatial conformations. So cis-trans isomerization belongs to isomerization.
If two carbon atoms on a double bond are connected to four completely different atoms or groups, then the two atoms or groups connected to each carbon atom are compared according to the "order rule". If the two better groups are on the same side of the π bond plane, they are Z isomers, and those on the other side are E isomers.
Order rule
(1) is determined by the atomic numbers of two atoms directly connected to the carbon of the double bond, and the larger the atomic number, the better. If the atomic numbers are the same, compare the relative atomic masses.
(2) If the first atom directly connected to the double bond carbon atom is the same, the second or even the third atom should be compared in turn, and so on until the priority order is compared.
Note: Shun, reverse, Z and E are two different labeling methods. Shun is not necessarily Z-shaped, but reverse is not necessarily E-shaped.
Cis-trans isomerization: also known as geometric isomerization, it belongs to one of functional group isomerization in structural isomerization of stereoisomerization. This isomerization phenomenon is generally caused by functional groups in the structure of organic compounds, such as C=C double bond, C≡C triple bond, C=N double bond, N=N double bond or alicyclic ring, which cannot rotate freely. Organic compounds containing this isomerism are called cis-trans isomers, and they are obviously different in physical, chemical and biological properties. Their nomenclature can be divided into cis-trans isomeric nomenclature and ze nomenclature. In addition, there may be, but not limited to, cis-trans geometric isomerism of coordination ions in coordination compounds.
Bezerius proposed that substances with the same composition but different properties should be called "isomerism". The discovery and theoretical elucidation of isomerism is an important step in the development of material composition and texture theory, which opens the study of molecular structure and promotes the development of organic chemistry.
After the discovery of the optical isomerism of tartaric acid,1September, 874, the Dutch physical chemist Jacobs Hendricks van tehoff (1852-1911) discussed Paster's pamphlet "worster El Tuo. 1874165438+10 In October, French chemist Joseph Achile Lebel (1847- 1930) published his papers in the Paris Bulletin of Chemical Society, and they can use geometric heterogeneity independently. Suppose that two tetrahedrons around two carbon atoms in a molecule are connected together along one side of the tetrahedron, indicating a double bond that cannot be rotated. Then, the hydrogen group and carboxyl group are placed in the two models so that they cannot overlap. It is not an optical isomer, and its physical properties are different, so cis-trans isomers are found. ? [ 1]?
1964, German chemist Xiao studied aliphatic hydrocarbons, carefully investigated the relationship between organic structure and properties, confirmed the unity of the four valence of carbon atoms, gave a reasonable explanation for the isomerization phenomenon, and shaped the theory of organic structure.