Alkyne - Structure, Properties and Uses
Any organic compound consisting of two elements, hydrogen (H) and carbon (C), is a hydrocarbon. Usually, the carbon atom is encircled by a hydrogen atom in a different configuration to form the molecular structure. Hydrocarbons are natural organic molecules abundant in nature and primary constituents of natural gas and petroleum. In addition, fossil fuels are found in plants and trees. Earlier hydrocarbons were classified according to their properties and origin, but in contemporary chemistry, hydrocarbons are distinguished according to their atomic structure rather than the source. There are four different kinds of hydrocarbons, namely, alkane, alkene, alkyne, and aromatic hydrocarbons.
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Structure of Alkynes
An alkyne is a hydrocarbon featuring at least one carbon to carbon triple bond with the general formula of alkynes \[C_n H_{2n-2}\] (C represents carbon, represents hydrogen and n represents the number of carbon atoms) stoichiometry.
Stoichiometry shows the relationship between reactants and or products to derive desired quantitative data. Two sets of overlapping p orbital bonds are shaped by the carbon triple bond, causing sp hybridization of the alkyne carbon. The structure of alkynes has rectilinear geometry with \[180^\circ\] bond angles. Triple bonds of alkyne are strapping, diminutive, and reactive. All alkynes contain one suffix representing carbon to carbon triple bond. Alkynes examples are ethyne (\[C_2 H_2\]), propyne (\[C_3H_4\]), and butyne (\[C_4H_6\]).
Alkanes and Alkenes
Alkanes have only one carbon bond; alkenes contain double carbon to carbon bonds. Alkanes are the simplest form of hydrocarbon with a single bond, molecular formula \[C_n H_{2n+2}\](C represents carbon, represents hydrogen and n represents the number of carbon atoms). The three most prevailing and less intricate alkanes are methane (\[CH_4\]), ethane (\[C_2H_6\]), and propane (\[C_3H_8\]). Like alkanes, alkenes are true hydrocarbons as no other element than hydrogen and carbon exist in them. In the structure of the alkene, for every double bond, there is at least one carbon atom, molecular formula \[C_2H_{2n}\]. Ethene (\[C_2H_4\]) and propane (\[C_3H_6\]) are the most common and least complex forms of alkenes.
Aromatic hydrocarbons contain only one hydrogen and a carbon atom. Their atomic structure is more intricate than other forms of true hydrocarbons. Aromatic hydrocarbons are more stable than alkanes, alkenes, and alkynes because of a benzene ring with or without. Due to the strong aroma attached to them, they are called aromatic hydrocarbons; the most common of them is benzene (\[C_6H_6\]).
Properties of Alkynes
The general formula of alkyne is \[C_n H_{2n-2}\], unsaturated carbon with a triple carbon bond. There are two types of alkynes: terminal and internal. In a terminal alkyne, carbon at the end of the series shares a triple bond with the carbon atom. In internal alkynes, the triple bond is between carbons none of them is terminal. Alkynes are nonpolar, unsaturated hydrocarbons with higher boiling points than alkanes and alkenes. Alkynes are totally insoluble in water but partially soluble in polar solvents and completely dissolved in organic solvents. The acidity of alkyne compounds is greater than alkanes and alkenes; because of linear configuration, the sp hybridized ones are most acidic. Alkyne series are more unstable due to the repulsion of electrons with high energy potential.
Chemical Properties of Alkynes
The Alkyne reaction is an addition due to the existence of loosely held pi-electrons. The existence of a triple bond permits water, halogens, and other substances to be added by the process of the addition reaction. The unsaturated compound, after undergoing additional reaction, turns into a saturated compound due to the supplemented group of atoms or molecules. Alkynes mix with water without reacting under normal conditions. But in the presence of dilute sulphuric acid and mercuric sulphate stimulates alkyne to react with water to form alkenes that instantly tautomerize (a net process of proton transfer from one site to another by a sequence of steps when the solvent is intermediary) to ketones.
Uses of Alkynes
Alkynes are used to prepare organic solvents, to fuel portable lamps known as acetylene lamps mounted on bicycles and homes. Acetylene (ethyne) is used to cut, weld materials that require a high-temperature\[3500^\circ\]. Acetylene is used to produce an array of inorganic compounds used for the synthesis of Vitamin A and E.
Conclusion
Alkynes are hydrocarbons that consist of a sequence of carbon and hydrogen atoms with no less than one triple carbon to carbon bond. These homologous series have a molecular formula of \[C_n H_{2n-2}\] . In longer alkyne series, additional carbon atoms are attached by a single covalent bond. Due to the triple bond, alkynes have restricted rotations but do not have stereoisomers because of sp hybridization.
FAQs on Alkyne
1. What are the uses of hydrocarbons?
Ans: Hydrocarbons have only two elements, hydrogen and carbon; these compounds are not themselves beneficial in medicine. But when modified, it becomes functional to form pharmaceutical drugs. Hydrocarbon derivatives extracted from crude oil are extensively used in cosmetics. It would not be an overstatement to say hydrocarbons are the driving force of the world economy. The most crucial use of hydrocarbons is fuel. The most common hydrocarbon fuels are gasoline, diesel oil, natural gas, kerosene, aviation fuel, and propane—methane, the lightest gas, is largely used for industrial and domestic heating. Methane is used in electrical power generation and for the production of methanol. In compressed liquid form, it is known as liquefied natural gas (LNG).
2 .What are the properties of aromatic hydrocarbons?
Ans: Aromatic hydrocarbons are extremely stable and less reactive than alkenes, making them ideal for industrial solvents for nonpolar compounds. This unsaturated hydrocarbon cyclic structured compound derives its name due to its fragrant property. The structure of aromatic hydrocarbons has a closed ring of alternate single and double bonds with delocalized electrons. The bonding is stronger than assumed, as all atoms in the ring share the delocalized electron density. Usual aromatic hydrocarbons are immiscible and non-reactive with water. The high ratio of carbon to hydrogen causes a sooty yellow flame. The aromatic substance is derived from multiple sources, including petroleum and coal tar.
3 .How do hydrocarbons affect global warming?
Ans: Hydrocarbons are organic compounds found in fossil fuels such as coal, natural gas, and crude oil. The combustion of hydrocarbon fuels releases carbon dioxide, and other greenhouse gases augment global warming and climate change. Impurities in fossil fuel cause byproduct emission, but combustion of hydrocarbon fuels inevitably produce carbon dioxide; the level of carbon dioxide emission depends on the chain length and molecular complexities of the hydrocarbon compound. The incomplete combustion of hydrocarbon fuels produces toxic, carcinogenic molecules that contaminate soil and groundwater. Methane, with the great potentiality of heat-trapping, contributes more to climate change than carbon dioxide. One of the most feasible and quick ways to reduce climate change is to replace the least energy-efficient fuel with more effective and cleaner fuel.
