# Why are silyl chlorides more readily hydrolysed than alkyl chlorides?

I know that the $\ce{Si-Cl}$ bond has a slightly higher energy, but silyl chlorides are much more readily hydrolyzed compared to alkyl chlorides. I do not fully understand why that is. My thoughts so far are:

• There is a better match in energy between the orbitals of the $\ce{Si-Cl}$ bond and water.

• Reactions proceed when there is a favorable interaction between HOMO and LUMO.

• In this case, the HOMO is the lone pair on the water molecule. The LUMO of a $\ce{Si-Cl}$ bond is closer to it in energy compared to a $\ce{C-Cl}$ bond.

Is this the right argument to take?

Using $\ce{CCl4}$ and $\ce{SiCl4}$ as the basis for comparison, there are several reasons.
1. The greater electronegativity difference between Si and Cl leads to a larger $\delta^+$ on silicon, making it more electrophilic and susceptible to attack by water.
3. It is possible that the hydrolysis of $\ce{SiCl4}$ proceeds via an alternative, faster pathway that involves a five-coordinate intermediate (as opposed to $\ce{CCl4}$, in which five-coordinate carbon does not occur).