A Level Chemistry OCR Practice Exam

Which process is an example of an elimination reaction?

1. Breaking down glucose into pyruvate

2. Removing water from ethanol to form ethene

3. Combining hydrogen and oxygen to form water

4. Oxidizing carbon to form carbon dioxide

The correct answer is: Removing water from ethanol to form ethene

The process of removing water from ethanol to form ethene is indeed an example of an elimination reaction. In this reaction, a molecule of water is eliminated from ethanol (C2H5OH), which results in the formation of ethene (C2H4). This type of reaction is characterized by the removal of small molecules to form a double bond in the product. In the case of ethanol, the elimination of water involves the breaking of a C–H bond and an O–H bond, leading to the formation of a carbon-carbon double bond in ethene. Elimination reactions are often associated with the formation of alkenes, as seen in this process, and they typically require certain conditions such as heating with an acid catalyst or dehydration. The transformation involves the loss of specific groups or atoms from the reactant to result in a product with a higher degree of unsaturation, which is evident in the conversion of a saturated alcohol into an unsaturated alkene. The other options do not fit the definition of an elimination reaction. Breaking down glucose into pyruvate is a metabolic process known as glycolysis, which involves several hydrolysis and oxidation reactions but does not focus on the removal of small molecules to create double bonds. Combining hydrogen and oxygen