Acid anhydrides are chemical compounds formed by the removal of water from an acid. They typically consist of two acyl groups bonded to the same oxygen atom. Common examples include acetic anhydride and phthalic anhydride, which are used in various industrial applications, such as the production of plastics and pharmaceuticals. These compounds can react with water to regenerate the corresponding acids, making them important in organic synthesis. Acid anhydrides are also known for their ability to react with alcohols to form esters, a reaction that is widely utilized in the creation of fragrances and flavorings.