Alkynes

Naming Alkynes
Definition of Alkynes :
Alkynes are organic chemical compounds that include a triple covalent bond between two carbon atoms.
That is, alkynes are the class (or "category") of organic hydrocarbon compounds that include a part consisting of two carbon atoms attached to each other by a triple covalent bond, which is usually represented in molecular diagrams as three parallel straight lines between the carbon atoms attached together by that triple bond.
Alkyne molecules can vary in size up to very long molecules most of which consist of carbon atoms attached to each other and also to hydrogen atoms.
Names of Alkynes in General
Alkynes are named according to the same system as other organic compounds, with the suffix -yne used to designate the presence in the molecule of a triple carbon-carbon bond.
The first step is to consider the number of carbon atoms forming a chain. If they are attached together in a linear (i.e. unbranched ) configuration then the number of carbon atoms is indicated according to the same system as used for naming alkanes (see the examples listed in the table below).
However, if the carbon atoms do not form a linear chain but include branches , the longest linear chain of carbon atoms within the molecule determines the base of the name of the compound, onto which is added information about the branches incl. their
lengths in terms of the number of carbon atoms in each branch (i.e. methyl- indicates a branch consisting of just one carbon atom attached to the main chain, ethyl- indicates a branch of two carbon atoms in length, etc.) and their positions along the longest linear carbon chain (e.g. attached to the 2nd carbon, 3rd carbon, etc.).
The simplest linear alkynes are named and their structures drawn in the following table.
Names and Structures of simple Linear Alkynes
The first ten members of the homologous series of linear alkynes with the triple bond attached to the first (=last) carbon atom is shown below.
The simple structures drawn below show bond types such as single and triple bonds, but not accurate bond angles.
Ethyne (C 2 H2 )
Simple Formula:
HCCH
Simple Structure:
* Examples of other / previous names:
acetylene
acetylen
ethenylene
ethine
ethin
vinylene
Propyne (C 3 H4 )
Simple Formula:
CH 3 CCH
Simple Structure:
* Examples of other / previous names:
1-propyne
prop-1-yne
methylacetylene
methyl acetylene
allylene
propylene tetramer
Butyne (C 4 H6 )
Simple Formula:
CH 3 CH 2 CCH
Simple Structure:
* Examples of other / previous names:
1-butyne
but-1-yne
butyne-1
ethylacetylene
ethyl acetylene
Pentyne (C 5 H8 )
Simple Formula:
CH 3 CH 2 CH 2 CCH
Simple Structure:
* Examples of other / previous names:
1-pentyne
pent-1-yne
acetylene
Hexyne (C 6 H10 )
Simple Formula:
CH 3 CH 2 CH 2 CH 2 CCH
Simple Structure:
* Examples of other / previous names:
1-hexyne
hex-1-yne
butylacetylene
n-butylacetylene
Heptyne (C 7 H12 )
Simple Formula:
CH 3 CH 2 CH 2 CH 2 CH 2 CCH
Simple Structure:
* Examples of other / previous names:
1-heptyne
hept-1-yne
amylacetylene
Octyne (C 8 H14 )
Simple Formula:
CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CCH
Simple Structure:
* Examples of other / previous names:
1-octyne
oct-1-yne
hexylacetylene
Nonyne (C 9 H16 )
Simple Formula:
CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CCH
Simple Structure:
* Examples of other / previous names:
1-nonyne
non-1-yne
Decyne (C 10 H18 )
Simple Formula:
CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CCH
Simple Structure:
* Examples of other / previous names:
1-decyne
octylacetylene
Why stop at ten carbon atoms (in the chain)? It doesn't.
There are more similar linear alkynes.
*Note : The synonyms indicated for compounds listed above are just some examples of alternative names found online and believed to have been used to refer to the substance indicated. They have not all been verified and may include common (non-scientific) names, trade names specific to particular suppliers, and perhaps errors. The purpose of these lists is to give a general indication of the range of names by which alkynes are known - both generally, and specifically. Knowledge of these alternative names is not usually required for A-Level Chemistry or other school exams.
See also the related page about functional groups in organic molecules , which includes the alkyne group, among others.
Note : This is one of many pages about types of organic compounds in our Organic Chemistry Section. Similar and related pages describe hydrocarbons , alkanes , haloalkanes, alkenes, alkynes , cycloalkanes, aromatic hydrocarbons (arenes), alcohols , esters ,
ethers, aldehydes , ketones , carboxylic acids ,
acid chlorides , acid anhydrides , azo dyes,
amines , amides , nitriles , amino acids (chemistry), peptides, proteins (chemistry), polypeptides and others. If you need further information ask your chemistry tutor.
According to the International Union of Pure and Applied Chemistry (IUPAC) recommendations for nomenclature of organic chemistry, compounds that include the -alkyne group functional group may be called
alkynes .