HSC · Topic explainer
Alkane bromination in HSC Chemistry
An alkane can react with bromine in ultraviolet light by free-radical substitution. A bromine atom replaces a hydrogen atom and the carbon skeleton stays intact. If the alkane has different hydrogen environments, more than one structural product may form. Use the displayed product to locate the bromine before you name it.
Worked example
Consider propane reacting with bromine under ultraviolet light. A hydrogen atom can be replaced by bromine while the three-carbon skeleton stays intact. This is substitution.
Replacing a hydrogen at the end gives 1-bromopropane. Replacing one on the middle carbon gives 2-bromopropane. If the question gives the product structure, use its bromine position to choose the name. In an addition reaction, by contrast, the reagents add across an unsaturated bond.
Official exam practice
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Further reading. NESA 2025 Chemistry marking feedback