Classifying Isomers

Establishing the isomeric relationship between two molecules plays an important part in predicting their relative chemistries. For example, as we have seen, discerning that two molecules are enantiomers tells us that they will behave identically under most chemical circumstances, whereas finding them to be diastereomers tells us that they will have distinctly different behaviors. The chart below represents the process of classification as a series of YES or NO decisions. Start with a pair of molecular structures, answer the boxed questions, and follow the appropriate arrows. An accurate classification will result.

Here are a few problems to use for practice with the flow chart. Some pairs are constitutional isomers, some are stereoisomers.

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