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Experiment 3 An Addition–Elimination Sequence: Preparation of a Bromoalkene

Two classes of reaction that are studied extensively in organic chemistry classes are additions and eliminations. In some ways they can be considered as opposites. Addition reactions involve the addition of a small molecule to a substrate. They are typical of unsaturated organic compounds such as alkenes and alkynes and may be considered as a process by which the double or triple bonds are fully or partially broken in order to accommodate additional atoms or groups of atoms in the molecule. For example, halogens undergo addition reactions with alkenes to yield di-halide products. Elimination reactions involve the loss of a small molecule from a substrate. They are the primary route by which organic compounds containing only single carbon-carbon bonds are transformed to compounds containing double or triple carbon-carbon bonds. Using these two processes in combination results in an overall substitution reaction.