Which of the following Newman projection has highest energy ?
The Correct Answer and Explanation is :
To determine which Newman projection has the highest energy, we need to analyze the types of interactions between atoms and groups in the molecule, particularly focusing on steric strain and torsional strain. In a Newman projection, the molecule is viewed down the bond between two atoms (typically carbon-carbon in alkanes or other organic molecules).
The following types of interactions can occur in Newman projections:
- Staggered Conformation: This is the most stable conformation. In this arrangement, the bonds on the front carbon are as far as possible from those on the back carbon, minimizing steric hindrance. The energy is lowest in this conformation because of the reduced repulsion between atoms and groups.
- Eclipsed Conformation: This is the least stable conformation. The atoms or groups on the front carbon are directly aligned with those on the back carbon, leading to a high level of torsional strain due to electron-electron repulsion. This is the highest energy conformation.
- Gauche Conformation: This is a type of staggered conformation where two substituents are 60° apart, leading to some steric strain, but not as much as the fully eclipsed conformation.
- Anti Conformation: This is a type of staggered conformation where the substituents on the front and back carbons are 180° apart. It is the most stable staggered conformation due to minimal steric hindrance.
Now, looking at these options:
- If the molecule is in an eclipsed conformation, it will have the highest energy. This is because eclipsed conformations result in maximal torsional strain and significant steric repulsion.
- In the staggered conformation, the energy will be lower, with anti being the most stable and gauche being less stable but still lower in energy than eclipsed.
Thus, if you have an eclipsed Newman projection in the choices, that would have the highest energy. The eclipsing interactions cause significant destabilization due to steric repulsions between adjacent bonds, raising the molecule’s energy compared to the staggered conformations.
In summary, the eclipsed Newman projection conformation has the highest energy due to increased steric and torsional strain.