Conformational analysis is a fundamental tool for assessing the three-dimensional spatial arrangements, energies, and stability of conformers influenced by intermolecular and intramolecular interactions. Rotational spectroscopy plays a crucial role in determining spectroscopic parameters by identifying their spectral fingerprints, while high-level quantum chemical calculations aid in the assignment of spectra and provide insights into conformational preferences and internal dynamics. In this thesis, we investigated the effect of different organic fragments on the conformational landscape of chalcogen-bridged compounds (oxygen vs sulfur). As previous microwave spectroscopic studies predominantly centered around small molecules containing O and S, our objective is to bridge this research void by analyzing relatively large and flexible molecules. We observed drastic differences in the conformational equilibria when transitioning from O to S bridged compounds, involving diallyl ether, diallyl sulfide, allyl ethyl ether, allyl ethyl sulfide, ethyl vinyl ether, ethyl vinyl sulfide, propyl vinyl ether, propyl vinyl sulfide, butyl vinyl ether, butyl vinyl sulfide. Additionally, we explored the effects of microsolvation through diallyl ether-water and diallyl sulfide-water complexes. A general trend emerged, indicating that the O-bridged compounds exhibit a competitive and rich conformational landscape in the presence of partially unsaturated side chains. However, the inclusion of saturated side chains with an increase in their length led to conformers being more close in terms of relative energies and to a greater number of conformers in S-bridged compounds compared to oxygen ones. Non-covalent interaction, natural bond orbital, quantum theory of atoms in molecules, and symmetry-adapted perturbation theory calculations, revealed the pivotal role of interactions involving the lone pairs of the central chalcogen atom (oxygen or sulfur) and the organic fragment in governing conformational preference and energy ordering. We also observed complex splitting patterns attributed to methyl internal rotations in molecules featuring a methyl group. The results presented here lay a solid foundation for future studies aimed at advancing the development and modeling of chemical bonds, dynamics, and reactivity of organochalogens and main group compounds.