Chapter 5, Problem 61IP

Interpretation Introduction

Interpretation:

Two stereoisomers of $\text{1,4-dimethylcyclohexane}$ has to be drawn and it should be explained why only two stereoisomers are observed for this molecule.

Concept introduction:

Cis-trans isomerism: In a compound with a Carbon-Carbon double bond, geometric isomerism is possible. The plane which is perpendicular to the pi-orbitals is considered the reference. There are a total of four substituents, two each at either of the carbons indulged in the double bond.

When two of the heaviest substituents are oriented on the same side of the reference plane, the geometric isomer is termed a ‘cis’-isomer.

When two of the heaviest substituents are oriented on the opposite sides of the reference plane, the geometric isomer is termed a ‘trans’-isomer.

Geometric isomers: Two atoms with the same side location of the double bond are called cis isomers and two atoms with opposite side locations of the double bond are called Trans isomers.

In a cyclic compound: The spatial orientation of the di substituents cyclic compound must be viewed as a three-dimensional conformation. Generally, a solid wedge bond indicates it is above the plane of the ring and a broken wedge bond indicates it is below the plane.

The stereoisomerism is the arrangement of atoms in molecules whose connectivity remains the same but their arrangement in different in each isomer.

The two molecules are described as stereoisomers if they are made of the same atoms connected in the same sequence, but the atoms are positions differently in space.

For $\text{1,4-disubstitutedcyclohexane}$ the same substituents on the axial or equatorial position gives the trans isomer while the same substituent on the axial and equatorial position gives the cis isomer.

Among this the equatorial isomer is more stable due to the absence of $\text{1,3-diaxial}\text{interactions}$.

Chiral centre: A chiral center is defined as the tetrahedral carbon atom in an organic molecule that is connected to four non-identical groups/substituents. It is sometimes known as a stereo genic center.