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3.2 Naming Cycloalkanes and Alkyl Halides

Lesson Summary

Naming cycloalkanes involves the same rules as naming alkanes with two additions:

  • 1. When there are two substituents on a cyclic molecule, their direction must be indicated with prefix “cis”, meaning “same side”, and “trans”, meaning “opposite sides”.

  • 2. If there are more than two substituents, “cis” and “trans” are no longer enough, and these substituents must be named with their stereochemical configurations (R/S system).

When naming alkyl halides, we follow the same rules for naming alkanes, except that we use prefixes “fluoro-“, “chloro-”, “bromo-”, or “iodo-”, to identify each halogen substituent. Alternatively, we may use suffixes “-yl fluoride”, “-yl chloride”, “-yl bromide”, or “-yl iodide”.