Question

For each of the following compounds, predict the energy barrier to rotation (looking down any one of the C-C bonds 2,2-dimethylpropane & 2-methylpropane

Answer 1

Rotation around single bonds leads to the formation of conformational isomers (conformers). The energy barrier to rotation around C–C bonds is generally small (usually less than 15 kcal/mole), leading to rapid rotation and interconversion of conformers. This prediction requires highly sophisticated ab initio molecular mechanics calculations coupled with DFT (Density Functional Theory) studies. We cannot predict directly and there is no universal formula for calculation. As we do not have such more expensive systems and softwares. But it was already published in reputed international journals.

I just gone through various journals and online library and find the below is more accurate one.