Hey,
I'm having trouble understanding a result of a chemist lab which involved computing the energies of molecules using software. I found the energies of (Z)- 1,1 diisopropyl ethene, (E) 1,1 diisopropyl ethene and 1,1 diisopropyl ethane to be -102.10 , -102.17, and -89.49 kJ/mol, respectively. I understand why the E isomer is more stable than the Z isomer, but why is the 1,1 diisopropyl ethane less stable than both of the others?

Question

Hey,
I'm having trouble understanding a result of a chemist lab which involved computing the energies of molecules using software. I found the energies of  (Z)- 1,1 diisopropyl ethene, (E) 1,1 diisopropyl ethene and 1,1 diisopropyl ethane to be -102.10 , -102.17, and -89.49 kJ/mol, respectively. I understand why the E isomer is more stable than the Z isomer, but why is the 1,1 diisopropyl ethane less stable than both of the others?

ggrree · Answer

I was thinking that the ability to rotate around the single bond would allow it to reduce any steric stress, but this isn't reflected in the software.  Why is this?