Transformational Isomers In Chemistry

The isomers which can be inter converted solely by rotation about formally single bonds in a form of stereoisomerism in chemistry studies are defined as conformational isomers. This phenomenon in chemistry is called as conformational isomerism. Conformational isomers are stereoisomers which arise from the rotation about sigma (σ) bond (single bond). It is usually fast interconverting in room temperature, causing in different arrangements of atoms in three-dimension space. The isomers which created in the specific conformational isomerism can be referred as conformers, or pointedly as rotamers. It is different with constitutional isomers, which have unlike linkages of atoms, different conformers have the same linkages of atoms and cannot usually

The staggered conformation in Newman projection has the lowest energy, which is the most steady arrangement. This is because all the C-H bonds are further away from another as possible due to the repulsion of electron clouds in the chemical bonds. So, the eclipsed conformation has the highest energy, means that it is the least steady arrangement as all the C-H bonds are arranged as near as possible.

Figure 2: Staggered and eclipsed conformations of ethane The eclipsed conformer has higher energy compared to staggered conformations. For an example, the eclipsed conformation of ethane has extra 2.9 kcal/mol of energy compared to staggered conformation of ethane. This is due to the torsional strain. Torsional strain can be also defined as eclipsing strain. It arises from the repulsive force between the electron clouds in the Carbon-Hydrogen bonds which are not sharing an atom and cause the increase of potential energy since the bonds are closed to each other in eclipsed conformer.

1.0 CONFORMATIONAL STEREOISOMERS OF BUTANE Butane can be presented in an infinite number of conformations. However, among them, there are only three conformers which have minimum potential energy, two gauche conformations and the anti-periplanar

So, as the bond rotation of butane continues, the molecule will reach the conformation situation of staggered and gauche. At this conformation, the butane also achieved the energy minima as it does not achieve the eclipsed conformation. The arrangement is staggered as the two methyl groups is 60°apart. This gauche conformation has the energy of 3.8 kJ/mol. The steric strain is arose due to the hydrogen atoms of the methyl groups are near to each other in the gauche conformation. Steric strain refers to the repulsive interaction that happens when atoms are forced to be close together over than their atomic radii allow and fill in the same