A Level Chemistry OCR Practice Exam

What type of reaction involves the removal of water from a saturated molecule to create an unsaturated molecule?

1. Dehydration

2. Hydration

3. Hydrolysis

4. Oxidation

The correct answer is: Dehydration

The process that involves the removal of water from a saturated molecule to create an unsaturated molecule is known as dehydration. During dehydration reactions, a water molecule is eliminated as two reactants combine, often resulting in the formation of a double bond or ring structure in the product, transforming a saturated compound (which contains single bonds) into an unsaturated one (which contains double or triple bonds). Dehydration is particularly significant in organic chemistry, such as when alcohols are converted into alkenes. For example, in the dehydration of ethanol, the removal of a water molecule results in the formation of ethylene, an unsaturated compound. In contrast, hydration refers to the addition of water to a molecule, hydrolysis involves the cleavage of bonds by the addition of water, and oxidation typically refers to a reaction involving the loss of electrons or an increase in oxidation state, rather than the removal of water.