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Nomenclature of Alkynes

A number of hydrocarbons, called alkynes or acetylenes, have triple bonds between carbon atoms.3 They conform to the general formula CnH2n-2 for one triple bond.

The IUPAC system for naming alkynes employs the ending -yne instead of the -ane used for naming of the corresponding saturated hydrocarbon:


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The numbering system for locating the triple bond and substituent groups analogous to that used for the corresponding alkenes:

Hydrocarbons with more than one triple bond are called alkadiynes, alkatriynes, and so on, according to the number of triple bonds. Hydrocarbons with both double and triple bonds are called alkenynes {not alkynenes). The chain always should be numbered to give the multiple bonds the lowest possible numbers, and when there is a choice, double bonds are given lower numbers than triple bonds. For example,

The hydrocarbon substituents derived from alkynes are called alkynyl groups:

For further information, below are step by step IUPAC rules on naming alkynes.

 

IUPAC Rules for Alkynes Nomenclature*

 

1.   The yne suffix (ending) indicates an alkyne or cycloalkyne.


2.   The longest chain chosen for the root name must include both carbons of the triple bond.

3.   The root chain must be numbered from the end nearest a triple bond carbon atom. If the triple bond is in the center of the chain, the nearest substituent rule is used to determine the end where numbering starts.


4.   The smaller of the two numbers designating the carbon atoms of the triple bond is used as the triple bond locator.


5.   If several multiple bonds are present, each must be assigned a locator number. Double bonds precede triple bonds in the IUPAC name, but the chain is numbered from the end nearest a multiple bond, regardless of its nature.


6.   Because the triple bond is linear, it can only be accommodated in rings larger than ten carbons. In simple cycloalkynes the triple bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest substituent rule.


7.   Substituent groups containing triple bonds are:
HC≡C–   Ethynyl group
HC≡CH–CH2   Propargyl group

 

Above are more examples of alkynes hydrocarbon.

Naming and drawing alkynes hydrocarbons video

Learning to names alkynes is simple so drop by and have fun!

 

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*http://www2.chemistry.msu.edu/faculty  /reusch/VirtTxtJml/nomen1.htm

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