Dialkylstannylene acetals are tin-containing species employed extensively as intermediates to facilitate high-yielding and regioselective monosubstitution reactions of diols or polyols with various electrophiles, which is an important application of organotin compounds in organic synthesis. Although an abundance of experimental studies of these reactions have been reported, the mechanism of the reaction has not been well defined. High-level theoretical methods are used in this thesis to investigate the chemistry of organotin systems at a molecular level. This involves the exploration of the geometry characteristics of the gas-phase structures along the reaction paths in order to understand the mechanism of the organotin-mediated alkylations of diols. Alkylation reactions which require strict conditions can be dramatically enhanced by the presence of nucleophiles. The effects of added nucleophiles were examined computationally by comparing reaction profiles obtained for alkylations of dimethylstannylene acetals in the presence of different nucleophiles.