Density functional theory has been used to investigate the reactions of 1,5 enynes with alcohols in the presence of a gold catalyst. We have compared the mechanism of the alcohol addition reaction for the enyne with that of the enyne where the carbon at position 3 is replaced with silicon. We find that different intermediates are present in both cases, and in the case of the silicon analogue, the intermediate that we find from the calculations is different from any that have previously been proposed in the literature. For the silicon analogue we have been able to rationalize the observed effects of alcohol concentration and nucleophilicity on the product distribution. For the carbon-based enyne we have shown why different products are observed depending on the substitution at position 3 of the enyne. Overall, we have provided for the first time a consistent explanation and rationalization of several different experiments that have been previously published in the literature. Our mechanism will assist in predicting the outcome of experimental reactions involving different alcohols, reagent concentrations, and substitution patterns of the 1,5 enynes.