Question

Relation between compound Z-1-chloro-1, 2-difluoropropene and Trans-1-chloro-1, 2 -difluropropene is (A) Optical isomers (B) Identical (C) Geometrical isomer (D) Conformational isomers

Short answer

The relationship between Z-1-chloro-1, 2-difluoropropene and trans-1-chloro-1, 2-difluoropropene is (C) Geometrical isomer. Both compounds have the same molecular formula and connectivity, but they differ in the arrangement of fluorine atoms around the double bond, with Z-configuration in one compound and trans-configuration in the other.

Step-by-step solution

Draw the molecular structures of the compounds

First, we need to draw the molecular structures of Z-1-chloro-1, 2-difluoropropene and trans-1-chloro-1, 2-difluoropropene. Z-1-chloro-1, 2-difluoropropene : C=C(Cl)(F)C(F)C(F) Trans-1-chloro-1, 2-difluoropropene : C=C(Cl)(F)CF_2

Define types of isomers

Next, let us understand the different types of isomers that are given in the exercise: (A) Optical Isomers: Stereoisomers that are non-superposable mirror images of each other. (B) Identical: Compounds having the same molecular formula and the same structural formula. (C) Geometrical Isomers: Stereoisomers with the same molecular formula and the same connectivity of atoms but different arrangement of atoms in space due to the presence of a double bond, a ring or other rigid structural element. (D) Conformational Isomers: Isomers that can be interconverted through rotation around a single bond, and are present in dynamic equilibrium with each other.

Comparing the compounds

Compare the structures of Z-1-chloro-1, 2-difluoropropene and trans-1-chloro-1, 2-difluoropropene to determine if they are Optical isomers, Identical, Geometrical isomer, or Conformational isomers. Both compounds have the same molecular formula: C_3H_2F_2Cl. However, the connectivity of atoms is different. In Z-1-chloro-1, 2-difluoropropene, the double bond is between the first carbon and the second carbon having a chlorine atom and fluorine atom each. In trans-1-chloro-1, 2-difluoropropene, the double bond is also between the first carbon and second carbon having a chlorine atom and fluorine atom each. The difference lies in the arrangement of the fluorine atoms around the double bond. Z-1-chloro-1, 2-difluoropropene has the Z-configuration, which means the two highest priority groups (chlorine and fluorine) are on the same side of the double bond. In contrast, trans-1-chloro-1, 2-difluoropropene has the trans-configuration, where the highest priority groups (chlorine and fluorine) are on opposite sides of the double bond. This makes them geometrical isomers. Answer: The relationship between Z-1-chloro-1, 2-difluoropropene and trans-1-chloro-1, 2-difluoropropene is (C) Geometrical isomer.

Key concepts

Stereochemistry

Stereochemistry is the branch of chemistry that focuses on the spatial arrangement of atoms within molecules and how this arrangement affects the physical and chemical properties of those substances. It's important to understand that molecules are three-dimensional entities, and the arrangement of atoms and groups within these molecules can result in different properties, even if they share the same molecular formula.

For instance, the concept of chirality arises from stereochemistry, where chiral molecules have non-superposable mirror images, much like our left and right hands. The study of stereochemistry also includes understanding the arrangement of atoms around double bonds, which gives rise to geometrical isomers, as demonstrated in the original exercise with Z-1-chloro-1, 2-difluoropropene and trans-1-chloro-1, 2-difluoropropene.

Isomerism in Organic Chemistry

Isomerism in organic chemistry refers to the phenomenon where compounds have the same molecular formula but differ in the arrangement of their atoms or groups. These differences can result in compounds with unique chemical and physical characteristics.

There are two main types of isomerism: structural (or constitutional) isomerism and stereoisomerism. Structural isomers have different connectivity of atoms, resulting in variations like chain isomerism, position isomerism, and functional group isomerism. Stereisomers, on the other hand, have the same connectivity but differ in their spatial arrangement. Subclasses of stereoisomers include geometrical and optical isomers. It's essential for students to grasp the differences between these types of isomers, as they can dramatically affect the properties and reactions of organic compounds.

Z-E Isomerism

Z-E isomerism, also known as cis-trans isomerism, is a form of geometrical isomerism that arises due to restricted rotation around double bonds or ring structures. The 'Z' stands for 'zusammen', which means 'together' in German, indicating that the highest priority groups are on the same side of the double bond. In contrast, the 'E' stands for 'entgegen', which means 'opposite', representing the highest priority groups on opposite sides of the double bond.

The priority of groups is determined by the Cahn-Ingold-Prelog priority rules, which depend on the atomic number of the atoms directly attached to the double bond or ring. In the case of Z-1-chloro-1, 2-difluoropropene and trans-1-chloro-1, 2-difluoropropene, the Z isomer has chlorine and fluorine on the same side of the double bond, whereas the trans isomer has them on opposite sides, defining their geometrical isomerism. Understanding Z-E isomerism is crucial in areas such as drug design and organic synthesis, as it affects the biological activity and chemical reactivity of molecules.