The alkynes or acetylenic hydrocarbons are hydrocarbons characterized by the presence of a carbon-carbon triple bond. Non-cyclic alkynes respond to the molecular formula CnH2n-2. They have an even higher degree of establishment than that of alkenes.
Among the chemical properties of alkynes highlights the fact that they are low polarity compounds, so insoluble in water, but quite soluble in common organic solvents such as ether, benzene, or carbon tetrachloride.
Theboiling and melting points of alkynes are very similar to those of alkanes or alkenes of equal carbon numbers. The effect on these physical constants, on the other hand, is more noticeable than the number of carbons and the presence of branches in the chain (which change in the same direction).
The simplest alkyne is acetylene, they follow the propylene (or tip) and the butino, which can be 1-butyne (triple bond at the end of the molecule) or 2-butyne (triple bond in the center of the molecule). These three are gases; those with the highest number of carbon atoms are liquids or solid.
Similar to alkenes, the triple bonds that characterize alkynes give them great chemical reactivity these substances and make them very prone to undergo addition reactions (hydrogen, halogens, water, etc.) and others. However, the three bonds that join one carbon atom with another are not equivalent: one of them (called the sigma bond) is stronger and acts as the main responsible for the union. The resulting compound can happen to have double bonds or only single bonds.
Compounds that have the triple bond at one end of the chain are called terminal alkynes; these compounds are characterized by their marked acidity. In fact, the terminal alkynes are the most acidic simple hydrocarbons. The length between carbon atoms in the bond is 1.20 amstrongs (even shorter than that of alkenes ─1.34 amstrongs─- and that of alkanes ─1.54 amstrongs─). Single, double and triple carbon-carbon bonds can coexist in the same molecule. When this happens, the hydrocarbon is named as an alkyne and the position of the double bond is indicated with the termination "ene", inserting it where appropriate
Examples of alkynes are listed below:
- ethyne (acetylene)
- tip
- 2- pentine
- 2-butyne
- 1-butyne
- October 3
- 2-nonino
- Methyl acetylene
- Ethyl acetylene
- 1-ene-4-hexyne
- Propyl acetylene
- Terbutyl acetylene
- 6,6-diethyl-4-noniino
- 5,6-dimethyl-3-heptin
- 3,3-diethyl-3,5-nonadiino
- cyclobutine
- 3-ethyl -5-ethynylhepta-1,6-diino
- 5-methyl-2-hexyne
- 3,5,7-decatriino
- 6-methyl-2,4-heptadiino
