Molecular compounds typically do not conduct electricity because they are composed of molecules held together by covalent bonds rather than ionic bonds. In these compounds, the electrons are shared between atoms, which results in the formation of neutral molecules. This means there are no free-moving charged particles, like ions or electrons, which are necessary for electrical conductivity.
When a molecular compound is in solid form, its molecules are arranged in a stable structure and are not free to move. Even when dissolved in water or melted, molecular compounds often do not produce ions. For example, sugar (a common molecular compound) dissolves in water but does not dissociate into charged particles, which is why it doesn’t conduct electricity well. In contrast, ionic compounds, which dissociate into ions when dissolved, allow for the flow of electricity. Therefore, the lack of free-moving ions in molecular compounds is the primary reason they do not conduct electricity.