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Anesthesia

Glossary Index

Anhydrous

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Definition

• Ananhydride is awater reactive compound that gives anacid or abase when combined with water.

Additional Info

Many substances are not themselves acids or bases, but will become such when exposed to water. This does not necessarily require the addition of water (such as from a fire hose). Many anhydrides will react readily with ambient humidity and even the water present in your skin or lungs!

The reaction of anhydrides with water is often very violent andexothermic (giving off a great deal of heat energy). Some examples of anhydrides and their reaction products with water include:

See the links under Further Reading below for the preparation and reactivity of other anyhydrides.

The reaction to form sulfuric acid is one step in the reaction of sulfur oxide emissions to form "acid rain". The reaction to formacetic acid is used in certain silicone caulks, leading to the familiar smell of vinegar (vinegar is a 5%solution of acetic acid in water) while the caulk cures.

MSDS Relevance

Treat anhydrides with great respect, keeping them away from water and recognizing that they can be as dangerous orcorrosive as their correspondingacid. Always wear properpersonal protective equipment, including chemical splash goggles and gloves when handling anhydrides.

Note above that reaction of anhydrides can often be violent andexothermic. Plan experiments and emergency procedures to deal with such situations before beginning your work.

Further Reading

• Derivatives of Carboxylic Acids, a lecture from the U of Southern Maine which includes discussion of anhydrides.
• Reactions of Acid Anhyrides With Water, Alcohols, and Phenol for youorganic chemists out there.
• Nomenclature of Anhydrides as well as theirpreparation and reactivity (see slides 55-60) at the U of Alberta.

See also:acid,base,hygroscopic,pH,water reactive.

Additional definitions fromGoogle andOneLook.