Staggered conformation of propane

All the staggered conformations of propane are equivalent to one another, and all its eclipsed conformations are equivalent to one another. The energy diagram resembles that of ethane in that it is a symmetrical one. 

In a Newman projection it doesn t matter which C you pick to be in the front or the back. All of the Newman projections shown here represent the staggered conformation of propane. 

All of the Newman projections shown here represent the staggered conformation of propane. 

In the eclipsed conformation of propane, we now have a larger CH3 close to H atom. This results in increased repulsive force or increased steric strain. The energy difference between the eclipsed and staggered forms of propane is greater than that of ethane. 

As in the case of ethane, two extreme conformations of propane are possible—in one the C-H and C—C bonds are staggered in the other they are eclipsed. 

Conformation and Conformational Analysis Conformation of Ethane Conformation of Propane Conformation of Butane Eclipsed and Staggered Eorms Ring Strains in Cycloalkanes Principles of Conformation 165... 

Follow this procedure for any C-C bond. With a Newman projection, always consider one C-C bond only and draw the atoms bonded to the carbon atoms, not the carbon atoms in the bond itself. Newman projections for the staggered and eclipsed conformations of propane are drawn in Figure 4.7. 

Newman projections for the staggered and eclipsed conformations of propane... 

Draw Newman projections for one staggered conformation and one eclipsed conformation of propane. 

Figure 3.8 Newman projections of propane showing staggered and eclipsed conformations. The staggered conformer is lower in energy by 14 kJ/mol.

In the eclipsed form of propane there is more steric hindrance than in the staggered form. There is also a greater torsional strain in the eclipsed form. As a result, the eclipsed form is expected to be higher in energy than the staggered form. Therefore the staggered conformation is more stable. The perspective formulas and Newman projections are sketched below ... 

---