IUPAC Nomenclature of Alkanes, Alkenes & Alkynes – Key Rules & Examples

15 question-and-answer flashcards covering the main IUPAC rules illustrated in the lecture notes, including parent chain selection, numbering priorities, handling of multiple bonds, and proper alphabetical ordering of substituents.

What determines the parent (base) chain in IUPAC nomenclature of hydrocarbons?

The longest continuous carbon chain that contains the highest-priority functional group or multiple bond (double/triple) present.

When both a multiple bond and substituents are present, which gets priority in choosing carbon numbering direction?

Numbering must give the lowest set of locants to the multiple bond (double or triple) before considering alkyl substituent positions.

How is the position of a double bond indicated in the IUPAC name of an alkene?

By the lowest-numbered carbon involved in the double bond, placed immediately before the parent name (e.g., 2-hexene).

Give the correct IUPAC name for C₆H₁₂ with its only C=C bond starting at carbon-2.

2-Hexene

What is the IUPAC name of the molecule commonly called isopentane?

2-Methylbutane

In the name 2,5-heptadiyne, what does the suffix “-diyne” tell you?

The molecule contains two triple bonds; their locants are at carbons 2 and 5.

How are two different double bonds in the same parent chain indicated?

Use the suffix “-diene” and list both locants, e.g., 1,3-butadiene.

Explain why the name 9-ethyl-5,6-dimethyl-7-propyl-3-decene lists ethyl first.

Substituents are alphabetized ignoring numerical prefixes (di-, tri-) and the prefixes sec- or tert-. ‘E’ (ethyl) comes before ‘M’ (methyl) and ‘P’ (propyl).

Which parts of substituent prefixes are NOT considered when alphabetizing substituents?

Multiplicative prefixes (di-, tri-, tetra-) and stereochemical designations (sec-, tert-). The ‘iso-’ prefix is alphabetized under I.

How are multiple identical substituents indicated in an IUPAC name?

Use multiplicative prefixes (di-, tri-, tetra-, etc.) along with all applicable locant numbers, e.g., 5,6-dimethyl.

Write the full IUPAC name for a 7-carbon chain with triple bonds at C-2 and C-5.

2,5-Heptadiyne

Which suffixes correspond to single, double, and triple carbon-carbon bonds in hydrocarbon IUPAC names?

-ane for single bonds, ‑ene for double bonds, ‑yne for triple bonds.

What is the correct order of components in an IUPAC hydrocarbon name?

Substituent(s) in alphabetical order + parent chain + suffix for multiple bond(s) + possible stereochemistry or functional group endings.

True or False: ‘tert-butyl’ is alphabetized under T.

False. ‘tert-’ is ignored; tert-butyl is alphabetized under B.

Why must you include locant numbers even when the position seems obvious in larger chains (e.g., 2-hexene versus hex-2-ene)?

Locants remove ambiguity, especially in longer or branched chains; IUPAC rules require explicit indication of the multiple bond’s position.