"Although the chemistry of carboxylic anhydrides is very similar to that of acyl halides, anhydrides have some practical advantages. Acyl halides are so reactive that they are difficult to store for extended periods without some hydrolysis occurring due to exposure to atmospheric moisture. As a result, chemists usually prepare acyl halides immediately before they are to be used. Anhydrides, being slightly less reactive toward nucleophiles, are more stable, and several (including all the examples illustrated in this section) are commercially available. Consequently, carboxylic anhydrides are often the preferred reagents for the preparation of many carboxylic acid derivatives."