Introduction and Naming
Start with the big picture
An acyclic, monounsaturated alkene has a C=C bond and the general formula CₙH₂ₙ; the corresponding alkyne has a C≡C bond and formula CₙH₂ₙ₋₂. For index of hydrogen deficiency, each double bond contributes one unit and each triple bond two. IUPAC naming begins with the longest chain containing the multiple bond, followed by numbering that gives the first multiple bond the lowest possible locant. The lesson’s broader framework covers bond-position suffixes, multiple identical bonds, substituent names, and names for compounds containing both double and triple bonds. It also introduces geometric descriptors for alkenes, cumulenes, terminal and internal alkynes, cycloalkenes, and the distinction between common and formal IUPAC names.
What you'll learn
- Distinguish alkenes from alkynes by their carbon–carbon bonds and acyclic monounsaturated formulas.
- Relate double and triple bonds to their contributions to index of hydrogen deficiency.
- Apply parent-chain selection, numbering, and suffix principles to multiple-bond names.
- Recognize naming considerations for geometric isomers, cumulenes, and cycloalkenes.
- Differentiate terminal from internal alkynes and identify relevant substituent names.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
