Petroleum processing results in the generation of significant quantities of elemental sulfur (S8), leading to a surplus of sulfur worldwide. Despite its abundance and low cost, the use of sulfur in value-added organic compound synthesis is limited due to its unpredictable and misunderstood reactivity. This dissertation aims to address this issue by tackling it from two angles. Firstly, by utilizing Density Functional Theory (DFT) calculations, the reactivity of sulfur in the presence of nucleophiles is studied. This facilitates the identification of organic polysulfide intermediates that can be generated under different conditions, as well as the corresponding reactivity for each type of nucleophile. This computational study begins with a benchmarking of numerous DFT functionals against experimental data and high-accuracy ab initio computations to determine the best functional(s) for studying elemental sulfur and polysulfides in organic reactions. Using the best DFT method, the mechanism of monosulfide formation from cyanide and phosphines is explained. At the end of this computational study, the mechanism of 2-aminothiophene formation via the Gewald reaction is elucidated. Secondly, attempts are made to synthesize sulfur-based organic compounds using elemental sulfur or compounds with a sulfur source through the utilization of boron, imine, and aryne chemistry. In summary, this dissertation aims to expand the use of sulfur in organic chemistry by providing an understanding to predict its reactivity with nucleophiles, as well as demonstrating its potential for the low-cost synthesis of valuable sulfur-based organic compounds
