The following non-systematic names are retained:
Examples to Rule A-3.1
The name "acetylene" for is retained.
3.3 - Unsaturated unbranched acyclic hydrocarbons having both double and triple bonds are named by replacing the ending "-ane" of the name of the corresponding saturated hydrocarbon with the ending "-enyne", "-adienyne", "-atrienyne", "-enediyne", etcNumbers as low as possible are given to double and triple bonds even though this may at times give "-yne" a lower number than "-ene". When there is a choice in numbering, the double bonds are given the lowest numbers.
3.4 - Unsaturated branched acyclic hydrocarbons are named as derivatives of the unbranched hydrocarbons which contain the maximum number of double and triple bonds. If there are two or more chains competing for selection as the chain with the maximum number of unsaturated bonds, then the choice goes to (1) that one with the greatest number of carbon atoms; (2) the number of carbon atoms being equal, that one containing the maximum number of double bonds. In other respects, the same principles apply as for naming saturated branched acyclic hydrocarbons. The chain is so numbered as to give the lowest possible numbers to double and triple bonds in accordance with Rule A-3.3.
Examples to Rule A-3.3
1,3-Hexadien-5-yne 3-Penten-1-yne 1-Penten-4-yne
The following name is retained for the unsubstituted compound only:
Examples to Rule A-3.4
3.5 - The names of univalent radicals derived from unsaturated acyclic hydrocarbons have the endings "-enyl", "-ynyl", "-dienyl", etc., the positions of the double and triple bonds being indicated where necessary. The carbon atom with the free valence is numbered as 1.
Examples to Rule A-3.5
Ethynyl 2-Propynyl 1-Propenyl 2-Butenyl 1,3-Butadienyl 2-Pentenyl 2-Penten-4-ynyl
The following names are retained (for unsubstituted radical only):
|Vinyl (for ethenyl)|
|Allyl (for 2-propenyl)|
See Recommendations'93 R-3.1.1
Examples to Rule A-3.6
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