Silicon forms very strong bonds to oxygen and fluorine (particularly to oxygen) – this provides a driving force for much of silicon’s chemistry.
Silicon is more electropositive than carbon, so when bonded to carbon it often represents an attractive site for nucleophilic attack (i.e. it has δ+) – particularly if a halogen is attached.
The mechanism for nucleophilic substitution is very similar to that for SN2, except that the 5-coordinate transition state in the latter is replaced by a 5-coordinate intermediate in the former. For example;
Carbocations β to silicon are stabilised by it.
Carbanions α to silicon are stabilised by it.
Silylcarbinols (see the example below for what a silylcarbinol is) can undergo 1,2-rearrangements if treated with a catalytic amount of base or active metal (e.g. Na/K alloy). The following example shows the mechanism of such rearrangements;