Ylides are a class of chemical compounds characterized by the presence of a positively charged atom, typically phosphorus or sulfur, bonded to a negatively charged atom, often a carbon atom. This unique structure allows ylides to act as intermediates in various chemical reactions, particularly in the formation of alkenes through a process known as Wittig reaction. Ylides are commonly used in organic synthesis due to their ability to react with carbonyl compounds, leading to the creation of new carbon-carbon bonds. Their versatility makes them valuable in the development of complex molecules, including pharmaceuticals and natural products.