Organosilicons 2

The high felixibility of silicones can be traced back to two things.

1. The low energy of the Si-O-Si bending vibration

While these bonds are normally zig-zagged, the planar form is stabilized by negative hyperconjugation, from the pi of oxygen to backlobe of the sigma* Si-Ch₃ orbital.

2. Low barriers of conformational changes around the Si-C bond:

Which is because unlike the C-CH₃ bonds, the diffuse Si orbitals cannot stabilize certain confirmations.