Illustrated Glossary of Organic Chemistry

Dehydration (desiccation): A process such as a chemical reaction that removes water.

Reaction of 1-methyl-1-cyclohexanol with aqueous sulfuric acid results in dehydration and formation of an alkene product. The atoms which constitute the molecule of water that is removed are shown in red. The reaction follows the E1 mechanism, as shown in this example.

CoCl2.  6 H2O		Anhydrous CoCl2

Gently heating CoCl₂ ^. 6 H₂O (red) causes it to dehydrate. The product is anhydrous CoCl₂ (blue). Watch a time lapse video.

Sucrose + H2SO4		Carbon + water vapor (steam)

The modern term 'carbohydrate' is a contraction of 'carbon hydrate'. Carbohydrates such as sucrose (C₁₂H₂₂O₁₁) where once thought of as 'carbon hydrates', having one molecule of water bonded to each carbon atom,  giving a molecular formula approximating C₁₂(H₂O)₁₂. While this is not an accurate structure for sucrose, its reaction with concentrated H₂SO₄ (a dehydrating agent) does produce carbon and water vapor (steam). Watch a video of this reaction.