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Unsaturated chemical compounds are those that have triple and double bonds in their chemical structures. Alkynes are unsaturated hydrocarbons because they have triple bonds in their chemical structure and are made up of carbon and hydrogen atoms.Hydrocarbons are the most basic organic compounds, consisting only of carbon and hydrogen. These can be found in nature in the form of objects that we use every day. As a result, hydrocarbons are regarded as the biological parents of organic compounds. All other compounds, on the other hand, are thought to have been created by substituting functional groups for one or more hydrogen atoms.
Preparation of alkynes:
Some of the most common alkyne preparation methods are as follows:
Dehydrogenation of Dihaloalkanes: Alkynes can be synthesized by dehydrohalogenation vicinal-di haloalkanes in an alcoholic solution of potassium hydroxide. As an illustration,
Dehalogenation of Tetrahalides: Tetrahaloalkanes dehalogenate and produce alkynes when heated in methanol with zinc dust. As an illustration,
Dehalogenation of Haloforms: Chloroform and iodoform dehalogenate and yield ethyne when heated with silver powder.
Synthesis of Ethyne from Carbon and Hydrogen: Steam from hydrogen gas can also be used to produce ethyne by passing it through an electric arc formed between two carbon electrodes. This method is known as Berthelot synthesis.
Properties of alkynes:
The properties of alkynes are essentially the same as those of alkanes and alkenes.
- Alkynes are unsaturated carbons that share three levels of security at the carbon site.
- Except for ethylene, which has a slight distinctive odour, all alkynes are scentless and dismal.
- The first three alkynes are gases, and the next eight are fluids. All alkynes above these eleven are solids.
- Alkynes have a somewhat polar nature.
- The boiling point and liquefying point of alkynes increase as their atomic design increases. The edge of boiling over increases as their subatomic mass increases.
- Furthermore, because of an additional bond at the carbon site, the limits of alkynes are marginally higher than those of their corresponding alkenes.
Chemical Properties of alkynes:
Acidic nature:
When it comes to the synthetic properties of alkynes, we begin with their marginally acidic nature. Alkynes are currently marginally electronegative in nature. Alkynes have sp hybridised triply fortified carbon particles, whereas alkanes have sp3 hybridised single bond iotas, resulting in electronegativity differences. This makes it easier for them to draw in the C-H bond’s common electron pair. So, when we react with ethyne to a solid base like NaNH2, we get sodium acetylide and free hydrogen (H2) gas. Such reactions, however, will not occur in alkanes and alkenes. In the end, hydrogen particles connected to the carbon-carbon triple bond in alkynes are slightly acidic. It should be noted that the other hydrogen particles exposing these are not acidic.
Addition reaction:
When the conditions are right, alkynes undergo hydration reactions. When alkynes react with halogens, hydrogen, and other similar elements, a saturated molecule is formed. Because they have a triple bond, they can accept two hydrogen atoms, halides, or halogens.
Dihydrogen addition: To speed up the process, a catalyst such as nickel, platinum, or palladium is used. When we add hydrogen to an alkyne, we get an alkene.
Halogen Addition: When alkynes and halogens such as chlorine react, the halogen bonds to the structure of the alkynes, resulting in halogen-substituted alkenes. The final product will be tetrachloroethane
Ethyne:
The chemical compound ethyne has the formula C2H2. It is the most basic alkyne and a hydrocarbon. This colourless gas is widely used as a fuel and a building block in chemistry. Because it is unstable in its pure form, it is usually handled as a solution. Although pure acetylene is odourless, commercial grades typically have a strong odour due to impurities such as divinyl sulphide and phosphine.
Acetylene is an unsaturated alkyne because its two carbon atoms are bonded together in a triple bond. With CCH bond angles of 180°, the carbon–carbon triple bond connects all four atoms in a straight line.
Conclusion:
Because ethyne has a very hot fire, it is commonly used in oxyacetylene gas welding and oxyacetylene gas cutting. When ethyne is ignited with oxygen, the resulting fire has a temperature of around 3600 Kelvin.Some pharmaceuticals contain alkynes, including the contraceptive noretynodrel. A carbon–carbon triple bond can also be found in pharmaceuticals. Ene-diynes are molecules with a ring containing an alkene (between two alkyne groups). These compounds, such as calicheamicin, are among the most potent antitumor agents available, so much so that the ene-diyne subunit is sometimes referred to as a “warhead.” Ene-diynes undergo Bergman cyclization, resulting in highly reactive radical intermediates that attack DNA within the tumour.
